Biodiversity

WEBVTT
Kind: captions
Language: en

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- [Instructor] Today, we're going to talk

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about biodiversity.

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So biodiversity as you might've guessed

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comes from two words,
biological and diversity.

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And essentially, it's the variations

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or the diversity present
between living things.

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Now, I grew up in the
sunny state of Arizona.

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And at first glance,

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there doesn't seem to be much variety

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in such a hot and dry place.

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I mean, it's the desert, right?

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But if we take a closer look

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at a place such as the Sonoran Desert,

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and here's a picture,

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we would find all kinds
of different living things

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like saguaro cacti,
jackrabbits, tarantulas,

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silver-haired bats and the roadrunner,

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which is my personal favorite.

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So we can say that the desert
is actually quite biodiverse.

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So in other words,

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it's home to a large
variety of living things.

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Since there are both big
and small differences

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between different living things,

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we can think of biodiversity
on three different levels.

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So the first and smallest scale level

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is going to be genetic biodiversity,

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which is just the genetic variation

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within a group of organisms.

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And a really great example
of this kind of biodiversity

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is the rock pocket mouse.

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And I know, that's a
mouthful of words to say.

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But it's really cute.

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I mean, look at this picture.

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So this is a species that can
actually be found right here

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in the Sonoran Desert.

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And the cool thing
about this mouse species

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is that there exists both tan

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and black-colored rock pocket mice.

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So even though both colored rodents

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come from the same species,

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there are genetic biodiversity

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creates mice with
completely different traits.

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And what's even more awesome

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is the fact that these
colors, tan and black,

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have come about due to natural selection.

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So scientists have found

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that there are more
black-colored rock pocket mice

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in places with dark black-ish lava rock.

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While there are more
tan-colored rock pocket mice

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in lighter colored sands.

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And this makes sense because
if you think about it,

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the mice are hunted from
above by predators like birds.

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So having a coat color that
blends into their surroundings

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would increase their chances of survival.

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So having this kind of genetic
biodiversity is really great,

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because the rock pocket mice

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can use many different colored
landscapes as habitats.

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And if let's say the
landscape color were to change

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and suddenly become
dominated by dark lava rock,

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then this population of mice

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would have the genetic diversity

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that it needs to adapt to this change.

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So the second level is
species biodiversity,

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which is the variety of
species in a particular area.

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So going back to the Sonoran Desert,

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there are all kinds of mammals and birds,

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plants, and insects.

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But what I think is
even more mind boggling

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is the sheer number of
bat species there are.

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I mean, we have silver-haired
bats, as I mentioned earlier.

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But also bats like spotted
bats, Western red bats,

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and even this kind of bat
called Peter's ghost-faced bat,

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which I think is a really awesome name.

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And you're probably thinking, okay, Abby,

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this is really interesting.

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But so what?

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Well, like genetic biodiversity,

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species biodiversity is
super duper important.

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Because having a lot of different species

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means that more roles can
be filled in an ecosystem,

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which makes the ecosystem healthier.

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So moving on to the final level,

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we have ecosystem biodiversity.

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And this is just the variety
of ecosystems on the planet.

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Now we've been talking a lot
about the Sonoran Desert.

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And a desert is actually a
type of ecosystem on earth.

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And if you recall,

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ecosystems are made up
of both living things

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and their physical environment.

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So in this case, living
things in the desert ecosystem

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could include things like
rattlesnakes, scorpions,

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and cacti.

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Well, non-living things
could include rock formations

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or a sand dunes.

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And in addition to desert ecosystems,

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earth has forest ecosystems,
coral reef ecosystems,

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all kinds of different ecosystems.

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And having all these
different kinds of ecosystems

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is extremely critical for our survival.

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Because the diversity
of ecosystems on earth

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provide us humans with important
resources and services.

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So without ecosystem biodiversity,

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our quality of life,

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and in fact, our very
survival could be at risk.

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So as you can tell, every
level of biodiversity

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is incredibly important
for unique reasons.

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Now, biodiversity doesn't remain constant.

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So we can think of biodiversity

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as something that can change over time.

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Now, the important thing to remember

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is that speciation increases biodiversity

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while extinction decreases biodiversity.

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So let's talk about speciation first.

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So speciation happens when
one species evolves into two

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or more species over time.

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And you might have heard

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or seen something that looks like this.

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And I'll draw it out
right here to the right.

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And this is just a very
simple speciation model

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or a phylogenetic tree.

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So we have here a common ancestor

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that branches off into
different species over time.

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This arrow representing
time or T for short.

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And it's speciation events like these

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that have led to the biodiversity

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that we see on earth today.

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On the flip side, we have extinction

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which causes biodiversity to decrease.

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And what we mean by this word
extinction is that a species

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or population of living
things dies off completely.

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So notice that it can happen
on different levels too.

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For example, if a population goes extinct,

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then we no longer have the
genetic variants in the gene pool

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or the set of genes for
a particular species.

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But if a species went extinct entirely,

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then that species is no longer there

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to fulfill its unique role
or its ecological niche.

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So you might've heard of the dodo bird,

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which is a species that
actually went extinct

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way back in the 1600s.

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So, some of the major causes

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behind the dodo birds extinction

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include over hunting, habitat loss

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and competition with some
newly introduced species.

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And unfortunately, the last dodo bird

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was reportedly killed in 1681.

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And even though we can't enjoy

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the presence of dodo birds anymore,

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learning about this extinct bird

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actually brings up a really good question.

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That is, what effect do humans have

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on biodiversity right now?

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Well, it's sad to say,

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but humans are actually causing
biodiversity to decrease.

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Things like climate change,
habitat destruction,

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and overexploiting resources

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have caused a huge loss of biodiversity.

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And if you remember having biodiversity

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is really critical to our survival,

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which is a big, oh, oh.

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In fact, species extinction

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is now occurring at a rate
of 100 to 1000 times faster

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than the background rate
detected in fossil records.

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And because the extinction rate

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is much bigger than the speciation rate,

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the result is an overall loss
or decrease in biodiversity.

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So today we learned about biodiversity,

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which is the variety of
life present on earth.

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We talked about three different
levels of biodiversity

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moving from genetic
biodiversity to species

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and then ecosystem biodiversity.

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And we also talked about how
biodiversity isn't stagnant

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or fixed in place.

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We have speciation events
that can increase biodiversity

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and extinctions that
decrease biodiversity.

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And finally, we learned that human actions

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are threatening biodiversity,

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as we currently have a
greater extinction rate

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than speciation rate.


Formation of biomolecules

WEBVTT
Kind: captions
Language: en

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- [Sal] So all organisms
need food to survive.

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Now, for some of you, this
might be pretty obvious.

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You realize what might happen to your body

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if you don't get food.

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You might realize that you
need that food for both energy

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and you need that to actually
build up your actual body.

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So you need it for matter as well.

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But some of you might be thinking,

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all right, I have a mouth.

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I understand where the food goes.

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I also understand what's left over

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when I'm done with the food.

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And so I must have extracted
some energy and matter from it,

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but you just said all organisms, Sal,

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and I'm looking outside of a window

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and I see a tree and a
tree does not have a mouth.

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A tree is an organism.

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How does it get its food?

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And the answer you might already realize

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is that the tree

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can make its own food
through photosynthesis.

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We've seen this in other videos.

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You have carbon dioxide in
the air and you have water.

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And the presence of energy
in the form of sunlight,

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through the process of
photosynthesis, would produce glucose

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and molecular oxygen as a byproduct.

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And you can count the various carbons

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that are in this dark gray color.

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Oxygen's in this red
color and hydrogen's here.

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And you can see that
everything all adds up.

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You have one, two, three,
four, five six carbons here

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in the six carbon dioxide molecules.

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And then you could see in this glucose,

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you have one, two, three,
four, five, six carbons.

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I encourage you to pause the video

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and make sure that the
oxygens are all accounted for

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between the glucose molecule
and this molecular oxygen,

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and that the hydrogens
are all accounted for.

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And so a plant can produce its own food,

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and then when they need it,

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they can metabolize that food

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through a process of respiration.

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It's really important to realize

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that respiration does
not just occur in your

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and my bodies.

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Even organisms like plants
need to break down the food

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that they produced if they
wanna use it for energy.

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Now, the question you might have is,

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where is the energy here?

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Just as it takes energy
to rearrange these atoms

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and molecules into glucose,
under the right conditions,

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through a metabolic pathway,

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you can go the other way around.

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And chemically, that will release
energy, which even a plant

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which isn't running around,
it isn't doing jumping jacks,

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it isn't talking.

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It needs energy just to be alive.

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All living things need
energy in order to exist,

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in order to maintain their
cells, in order to reproduce.

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So many of you all have
probably heard the term

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carbohydrate when we're
thinking about food

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or when we're thinking
about an energy context.

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And it's important to note
that this glucose molecule here

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is an example of a carbohydrate.

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It's not the only example of it,

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but one question might be,

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why is it even called a carbohydrate?

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Well, when you break
down the different parts,

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it seems like it would involve carbon.

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Right over here, you have the carbo part.

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And it seems like it's somehow

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involving water: carbohydrate.

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And that's because early chemists,

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they didn't actually
understand the structure

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of a carbohydrate the way that we do now.

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All they saw was the
ratio between the carbons,

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the hydrogens and the oxygens.

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That for every carbon.

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So let's say there are N carbons,

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there's going to be
twice as many hydrogens,

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and N oxygens as well.

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So one thing, one way to think about it,

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for every single carbon, you have an H2O.

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So every carbon, you have a water.

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So that's why early chemists,

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when they saw this ratio,
they called it carbohydrates.

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Glucose is a very simple carbohydrate,

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but you can make up chains
of things like glucose

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to build up more complex carbohydrates.

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Now it's important to realize

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that these types of molecules
aren't just used for energy.

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They can also be used for matter.

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The more that you study biochemistry,

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you're going to see a lot
of different molecules

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that are made up of these building blocks

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of carbons, oxygens, and hydrogens.

00:04:07.740 --> 00:04:10.130
And sometimes you might
even recognize structures

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that look a little bit like glucose,

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or look like things that
have been put together

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from some of these basic building blocks.

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For example, this molecule right over here

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is known as thymidine monophosphate,

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and it's a fancy name.

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But you can look at the
building blocks here.

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The monophosphate, you
have a phosphate group

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right over here.

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Thymidine comes from this
part of the molecule.

00:04:33.880 --> 00:04:36.610
It's sometimes known as a nitrogenous base

00:04:36.610 --> 00:04:39.600
because it has nitrogen that
you see in blue over here.

00:04:39.600 --> 00:04:42.430
And then right over here,
connecting the pieces,

00:04:42.430 --> 00:04:46.730
you have a five carbon sugar: Ribose.

00:04:46.730 --> 00:04:48.670
Now glucose is a six carbon sugar,

00:04:48.670 --> 00:04:50.650
Ribose is a five carbon sugar,

00:04:50.650 --> 00:04:52.280
but there are metabolic pathways

00:04:52.280 --> 00:04:53.960
where you can go from five carbon sugars

00:04:53.960 --> 00:04:56.280
to six carbon sugars, and back and forth.

00:04:56.280 --> 00:04:57.210
And what's interesting

00:04:57.210 --> 00:04:59.894
about things like thymidine monophosphate

00:04:59.894 --> 00:05:02.760
is it is a building block for something

00:05:02.760 --> 00:05:06.420
that is very, very, very important: DNA.

00:05:06.420 --> 00:05:08.510
Thymidine monophosphate is a nucleotide

00:05:08.510 --> 00:05:10.390
with a nitrogenous base thymine.

00:05:10.390 --> 00:05:12.610
You put a bunch of these
nucleotides together,

00:05:12.610 --> 00:05:16.130
not all of them have a
nitrogenous base of thymine here,

00:05:16.130 --> 00:05:19.290
but they form this double
helix structure that we study

00:05:19.290 --> 00:05:21.720
in a lot of depth in
many, many other videos.

00:05:21.720 --> 00:05:24.270
And you might already realize that DNA

00:05:24.270 --> 00:05:26.360
is the molecular basis of inheritance.

00:05:26.360 --> 00:05:31.000
We could not be who we are
without these types of molecules.

00:05:31.000 --> 00:05:32.890
Now, what's also
interesting is how do these

00:05:32.890 --> 00:05:35.740
different constituent
molecules rearrange themselves,

00:05:35.740 --> 00:05:39.130
even in the presence of energy,
to make other molecules?

00:05:39.130 --> 00:05:42.259
Or to get energy, how do
they re-rearrange themselves

00:05:42.259 --> 00:05:44.040
to release that energy?

00:05:44.040 --> 00:05:47.700
And all of these metabolic
pathways are facilitated

00:05:47.700 --> 00:05:50.220
by what are known as enzymes.

00:05:50.220 --> 00:05:53.370
And just to give an example of an enzyme

00:05:53.370 --> 00:05:56.470
this big thing here is commonly known

00:05:56.470 --> 00:05:58.210
as the Rubisco enzyme.

00:05:58.210 --> 00:05:59.430
Now you don't have to know its name

00:05:59.430 --> 00:06:01.140
at this point in your careers,

00:06:01.140 --> 00:06:03.870
but this is one of the enzymes
in the metabolic pathways

00:06:03.870 --> 00:06:06.650
that's able to take carbon dioxide

00:06:06.650 --> 00:06:08.530
and attach it to another molecule

00:06:08.530 --> 00:06:12.840
that eventually can get us to
forming a glucose molecule.

00:06:12.840 --> 00:06:15.450
And what happens here is
the various constituents

00:06:15.450 --> 00:06:18.170
attach to different
parts of these enzymes.

00:06:18.170 --> 00:06:20.590
And these enzymes change
their shape as they attach

00:06:20.590 --> 00:06:23.330
to certain things and they
can jam things together.

00:06:23.330 --> 00:06:25.170
They can synthesize other molecules

00:06:25.170 --> 00:06:27.840
or they can even help to break them apart.

00:06:27.840 --> 00:06:29.510
And it all comes full circle

00:06:29.510 --> 00:06:32.690
because the enzymes
themselves, these are proteins.

00:06:32.690 --> 00:06:34.830
These are made up of amino acids,

00:06:34.830 --> 00:06:36.728
which themselves are made up

00:06:36.728 --> 00:06:39.610
of a lot of these building block molecules

00:06:39.610 --> 00:06:41.981
that contain your carbons, your oxygens,

00:06:41.981 --> 00:06:44.300
and your hydrogens in them.

00:06:44.300 --> 00:06:46.050
I'll let you go now.

00:06:46.050 --> 00:06:47.440
But the important thing is to realize

00:06:47.440 --> 00:06:49.600
is that we have whole universes occurring

00:06:49.600 --> 00:06:51.800
in our cells, and that
all of these molecules

00:06:51.800 --> 00:06:54.850
and biological systems are
connected in different ways.

00:06:54.850 --> 00:06:56.150
And you have a whole series

00:06:56.150 --> 00:06:58.370
of metabolic pathways that are facilitated

00:06:58.370 --> 00:07:03.150
by enzymes that take one set
of things and step-by-step,

00:07:03.150 --> 00:07:06.798
put them together or break them apart

00:07:06.798 --> 00:07:11.410
in order to do all of the
different biological functions

00:07:11.410 --> 00:07:14.163
that we know are necessary for life.


Photosynthesis

WEBVTT
Kind: captions
Language: en

00:00:00.740 --> 00:00:02.530
- Hey everybody, Dr. Sammy here,

00:00:02.530 --> 00:00:04.460
your friendly neighborhood entomologist.

00:00:04.460 --> 00:00:08.173
And today, we're gonna
talk about photosynthesis.

00:00:09.420 --> 00:00:10.990
There's very little life on this planet

00:00:10.990 --> 00:00:13.570
that could exist without photosynthesis.

00:00:13.570 --> 00:00:15.430
It is the prerequisite for pretty much

00:00:15.430 --> 00:00:17.190
everything you see around you.

00:00:17.190 --> 00:00:20.020
It's how you get from the
intangible light of the sun

00:00:20.020 --> 00:00:22.860
to physical bodies like
those of humans are

00:00:22.860 --> 00:00:25.180
hungry, hungry caterpillars.

00:00:25.180 --> 00:00:27.963
But what does photosynthesis
actually mean?

00:00:28.860 --> 00:00:31.340
I hear people say all the
time, that photosynthesis

00:00:31.340 --> 00:00:36.340
is the process by which
plants make sugar from light.

00:00:38.260 --> 00:00:39.950
And it almost seems like magic.

00:00:39.950 --> 00:00:42.110
Light is not a substance.

00:00:42.110 --> 00:00:44.500
It is not made up of the
molecular building blocks

00:00:44.500 --> 00:00:45.940
that compose all matter.

00:00:45.940 --> 00:00:47.920
And thus, it doesn't have mass.

00:00:47.920 --> 00:00:51.320
You can fill a room with light
and never run out of space.

00:00:51.320 --> 00:00:55.100
So how could you possibly make
something physical out of it?

00:00:55.100 --> 00:00:57.170
Well, you can't.

00:00:57.170 --> 00:01:01.930
So, instead light is a form of energy,

00:01:01.930 --> 00:01:04.313
energy being the capacity to do work.

00:01:06.940 --> 00:01:09.430
So, this is where it's
helpful to know word origin.

00:01:09.430 --> 00:01:13.800
The word photosynthesis is
made up of two Greek words.

00:01:13.800 --> 00:01:18.800
It literally means light and
to put together, that's right.

00:01:19.030 --> 00:01:20.750
In addition to being an entomologist,

00:01:20.750 --> 00:01:22.870
a double a little bit in
etymology, just to make sure

00:01:22.870 --> 00:01:25.090
I'm maximally confusing to people.

00:01:25.090 --> 00:01:28.880
Anyway, you're literally
using light to drive reactions

00:01:28.880 --> 00:01:32.890
that combine ingredients into
new products, a form of work.

00:01:32.890 --> 00:01:37.060
So you're not turning light
itself into material sugar.

00:01:37.060 --> 00:01:41.360
You're taking matter that
already exists in the form of

00:01:41.360 --> 00:01:43.700
six molecules of carbon dioxide,

00:01:43.700 --> 00:01:45.780
six molecules of liquid water,

00:01:45.780 --> 00:01:49.800
and using the energy of
the sun to power a reaction

00:01:49.800 --> 00:01:52.400
that combines them into a new substance

00:01:52.400 --> 00:01:55.203
with molecular oxygen as a byproduct.

00:01:56.310 --> 00:01:57.610
Think of it this way.

00:01:57.610 --> 00:02:01.360
When you bake a cake, you
don't say that you made cake

00:02:01.360 --> 00:02:02.680
from heat.

00:02:02.680 --> 00:02:04.680
It would be more accurate to say

00:02:04.680 --> 00:02:09.680
that you took flour,
eggs, sugar, and butter

00:02:10.150 --> 00:02:13.123
and used heat to combine
them into something new.

00:02:14.790 --> 00:02:16.370
So sticking with our analogy,

00:02:16.370 --> 00:02:19.700
the ingredients for photosynthesis
are just carbon dioxide

00:02:19.700 --> 00:02:22.453
from the atmosphere and
water from the ground,

00:02:23.690 --> 00:02:26.580
with light to do the heavy lifting.

00:02:26.580 --> 00:02:30.960
Carbon dioxide and water are put together

00:02:30.960 --> 00:02:34.030
to produce a carbohydrate
which literally means

00:02:34.030 --> 00:02:35.143
water and carbon.

00:02:36.000 --> 00:02:39.150
As you can see with this
typical carbohydrate molecule,

00:02:39.150 --> 00:02:43.130
glucose, your carbon is
attached to the same atoms

00:02:43.130 --> 00:02:46.320
that compose water, two
hydrogens and oxygen.

00:02:46.320 --> 00:02:49.820
This carbohydrate has more chemical energy

00:02:49.820 --> 00:02:54.350
or bond energy than the molecules
of water or carbon dioxide

00:02:54.350 --> 00:02:56.200
that served as ingredients.

00:02:56.200 --> 00:02:59.930
Thus, the energy at the end
of the process is much greater

00:02:59.930 --> 00:03:03.170
than the energy that the
ingredients had at the outset.

00:03:03.170 --> 00:03:06.790
This means that photosynthesis
is a sort of useful reaction

00:03:06.790 --> 00:03:10.630
that stores energy like a
big biochemical solar cell.

00:03:10.630 --> 00:03:13.820
We call these endergonic reactions.

00:03:13.820 --> 00:03:15.250
And you might be able to see already

00:03:15.250 --> 00:03:18.040
why they will be so valuable
in biological systems.

00:03:18.040 --> 00:03:20.790
You take molecules that
don't have much energy

00:03:20.790 --> 00:03:23.640
and use them to produce
something that can do work.

00:03:23.640 --> 00:03:25.500
And the kitchen where
all this work happens

00:03:25.500 --> 00:03:26.770
is the chloroplast.

00:03:26.770 --> 00:03:29.201
Literally, the green maker.

00:03:29.201 --> 00:03:32.040
The chloroplast is a
little organ or organelle

00:03:32.040 --> 00:03:33.920
present in some plant cells.

00:03:33.920 --> 00:03:37.890
And it's what makes plant cells
and ultimately plants green.

00:03:37.890 --> 00:03:41.720
And this is because the
chloroplasts bear the green pigment

00:03:41.720 --> 00:03:42.553
chlorophyll.

00:03:44.080 --> 00:03:46.490
Now the same way that
the word photosynthesis

00:03:46.490 --> 00:03:49.410
can be broken down neatly
into its two base words.

00:03:49.410 --> 00:03:52.200
The process itself can
be separated into two

00:03:52.200 --> 00:03:53.590
neat little segments.

00:03:53.590 --> 00:03:55.910
I like to think of them
as a charging step,

00:03:55.910 --> 00:03:59.260
where energy from light is
converted into chemical energy

00:03:59.260 --> 00:04:02.270
and synthesis step where the
energy is used to do the work

00:04:02.270 --> 00:04:04.540
of actually synthesizing the end product,

00:04:04.540 --> 00:04:06.113
typically a carbohydrate.

00:04:07.160 --> 00:04:09.610
So the first segment requires
the direct input of light

00:04:09.610 --> 00:04:13.590
and as such is referred to as
the light dependent reactions.

00:04:13.590 --> 00:04:15.800
These happened in a
section of the chloroplast

00:04:15.800 --> 00:04:17.280
called the thylakoids.

00:04:17.280 --> 00:04:18.960
They form these neat little pouches.

00:04:18.960 --> 00:04:21.780
The inside of which is called
the lumen and the outside

00:04:21.780 --> 00:04:23.060
called the stroma.

00:04:23.060 --> 00:04:25.210
When a photon of light ends
it's eight minute journey

00:04:25.210 --> 00:04:27.670
from the surface of the sun
to the surface of a leaf

00:04:27.670 --> 00:04:29.590
its energy is absorbed by the chlorophyll

00:04:29.590 --> 00:04:31.810
embedded in the thylakoid membrane.

00:04:31.810 --> 00:04:35.600
This energy powers a pump which
literally charges the inside

00:04:35.600 --> 00:04:39.183
of the thylakoids like a battery
by moving the ions inside.

00:04:40.150 --> 00:04:43.760
As the charge builds up, the
energy can be used to do work.

00:04:43.760 --> 00:04:47.040
But the next segment of
this process happens outside

00:04:47.040 --> 00:04:49.760
of the thylakoids in the stroma.

00:04:49.760 --> 00:04:51.580
So they get that energy where it's needed.

00:04:51.580 --> 00:04:53.480
The thylakoids transfers the energy

00:04:53.480 --> 00:04:57.700
to a molecule called ADP,
adenosine diphosphate.

00:04:57.700 --> 00:04:59.350
By adding another phosphate bond

00:04:59.350 --> 00:05:02.443
and making it ATP, adenosine triphosphate.

00:05:03.320 --> 00:05:04.912
Now you might've heard of this one.

00:05:04.912 --> 00:05:08.052
It's often called the
energy currency of the cell.

00:05:08.052 --> 00:05:10.960
Pretty much wherever energy
is needed for cell to do work

00:05:10.960 --> 00:05:12.209
ATP is involved.

00:05:12.209 --> 00:05:16.160
You might have also heard that
the energy is stored inside

00:05:16.160 --> 00:05:20.230
of the phosphate bonds,
and that breaking them

00:05:20.230 --> 00:05:22.500
releases the energy.

00:05:22.500 --> 00:05:25.710
But try to remember that these
bonds depicted by the lines

00:05:25.710 --> 00:05:28.410
in these diagrams are just a convention.

00:05:28.410 --> 00:05:30.960
It represents an adherence
of these atoms together

00:05:30.960 --> 00:05:34.290
via attraction, and it
shows you where they adhere.

00:05:34.290 --> 00:05:36.983
But the energy isn't actually in the bond,

00:05:38.060 --> 00:05:41.550
the attraction between the
atoms builds up potential energy

00:05:41.550 --> 00:05:45.120
like a rubber band that's
being pulled really tightly.

00:05:45.120 --> 00:05:48.680
When you let it go, it
could hit a paper cup

00:05:48.680 --> 00:05:51.240
and do the work of displacing that cup.

00:05:51.240 --> 00:05:53.070
The rubber band then falls to the ground

00:05:53.070 --> 00:05:56.820
in a low energy state because
it's energy has been released.

00:05:56.820 --> 00:05:59.120
So when you put the energy into a system

00:05:59.120 --> 00:06:02.020
great enough to overcome the
attraction between the atoms

00:06:02.020 --> 00:06:05.270
and force them apart,
thereby breaking the bonds,

00:06:05.270 --> 00:06:08.480
atoms or in this case
a whole phosphate group

00:06:08.480 --> 00:06:11.150
can go spiraling off taking what was

00:06:11.150 --> 00:06:12.710
potential energy with it.

00:06:12.710 --> 00:06:14.593
If it hits something that it can bond with

00:06:14.593 --> 00:06:17.300
that energy is released
as the bond is formed

00:06:17.300 --> 00:06:21.050
and can be used to do work
such as the magic of ATP

00:06:21.050 --> 00:06:23.860
is described as energetic
because it's easy

00:06:23.860 --> 00:06:27.160
to break the bond between it
and the last phosphate group.

00:06:27.160 --> 00:06:29.820
Meaning you don't have
to put much energy in

00:06:29.820 --> 00:06:31.843
but you get a ton of energy out.

00:06:33.450 --> 00:06:35.130
So back to the thylakoids.

00:06:35.130 --> 00:06:37.250
Those photons of light were able to net us

00:06:37.250 --> 00:06:40.300
a highly energetic ATP molecule.

00:06:40.300 --> 00:06:42.310
But the next segment of photosynthesis

00:06:42.310 --> 00:06:44.210
is gonna need some electrons too.

00:06:44.210 --> 00:06:45.990
That light energy is used to do the work

00:06:45.990 --> 00:06:48.650
of loading up a mobile
electron carrier with electrons

00:06:48.650 --> 00:06:50.200
and a proton.

00:06:50.200 --> 00:06:52.740
This carrier is called NADP plus.

00:06:52.740 --> 00:06:54.710
And when it's got a full
load to take to the next

00:06:54.710 --> 00:06:57.313
set of reactions, it's called NADPH,

00:06:58.810 --> 00:07:01.100
and that's pretty much the
light dependent reactions

00:07:01.100 --> 00:07:02.160
in a nutshell.

00:07:02.160 --> 00:07:06.210
The only other thing you should
probably remember is that,

00:07:06.210 --> 00:07:09.430
well, this is where all the
oxygen in your lungs comes from.

00:07:09.430 --> 00:07:11.870
So, you know, no big deal.

00:07:11.870 --> 00:07:14.940
When chlorophyll gets excited
by that photon of light

00:07:15.890 --> 00:07:17.980
it turns into a real bully.

00:07:17.980 --> 00:07:20.260
The work it's doing
creates such a powerful

00:07:20.260 --> 00:07:22.890
electro-chemical imbalance
and the chlorophyll

00:07:22.890 --> 00:07:25.560
balances the equation by
just stealing an electron

00:07:25.560 --> 00:07:26.610
from water.

00:07:26.610 --> 00:07:29.550
This causes water to fall
apart releasing its oxygen

00:07:29.550 --> 00:07:31.583
which the plant just lets go of.

00:07:32.580 --> 00:07:34.350
So now that we've taken
care of the section

00:07:34.350 --> 00:07:37.430
that's dependent on light,
let's discuss the section

00:07:37.430 --> 00:07:38.263
that isn't.

00:07:39.750 --> 00:07:43.420
The light independent
reactions or the Calvin cycle

00:07:43.420 --> 00:07:45.770
occur in the stroma of the chloroplast.

00:07:45.770 --> 00:07:48.000
And this is where the earth shattering

00:07:48.000 --> 00:07:51.140
chemical reaction occurs
that allows for all life

00:07:51.140 --> 00:07:52.060
on this planet.

00:07:52.060 --> 00:07:55.660
The fixation of gaseous
carbon or inorganic carbon

00:07:55.660 --> 00:07:58.193
into carbon chains, organic carbon.

00:07:59.120 --> 00:08:01.330
And this is so important because fixation

00:08:01.330 --> 00:08:03.053
doesn't just happen on its own.

00:08:03.980 --> 00:08:07.370
CO2 in the atmosphere doesn't
form organic chains or sugars.

00:08:07.370 --> 00:08:10.010
When it bumps into more
CO2 in the atmosphere

00:08:10.010 --> 00:08:13.390
it requires the help of
enzymes and energetic molecules

00:08:13.390 --> 00:08:15.140
made by living organisms.

00:08:15.140 --> 00:08:17.780
It's why when we first
landed a rover on Mars

00:08:17.780 --> 00:08:19.870
we immediately started
looking for the evidence

00:08:19.870 --> 00:08:21.320
of organic molecules.

00:08:21.320 --> 00:08:25.660
It will be evidence that
something is or was living there.

00:08:25.660 --> 00:08:28.680
In the light independent
reactions a plant enzyme

00:08:28.680 --> 00:08:33.020
fixes carbon dioxide from the
air into a chain of carbon.

00:08:33.020 --> 00:08:35.750
So ATP and NADPH which were produced

00:08:35.750 --> 00:08:38.720
in the light dependent
reactions, provide the energy

00:08:38.720 --> 00:08:42.490
and the electrons to create two
energetic reactive molecules

00:08:42.490 --> 00:08:44.120
that can be combined to make glucose

00:08:44.120 --> 00:08:46.443
or other useful molecules.

00:08:47.360 --> 00:08:49.770
And the beauty of it
is that the byproducts

00:08:49.770 --> 00:08:54.770
of the light independent
reactions, ADP and NADP plus

00:08:55.270 --> 00:08:58.540
are shuttled off from the
stroma back to the thylakoids

00:08:58.540 --> 00:09:00.920
for more light dependent reactions

00:09:00.920 --> 00:09:03.140
where they can be recharged and recycled

00:09:03.140 --> 00:09:04.343
for use again later.

00:09:05.350 --> 00:09:09.300
And, wow, photosynthesis.

00:09:09.300 --> 00:09:11.710
The takeaway here is that photosynthesis

00:09:11.710 --> 00:09:16.020
allows you to go from the
intangible energy of the sun

00:09:16.020 --> 00:09:17.930
to the stored chemical energy

00:09:17.930 --> 00:09:20.780
that life on this planet is based on.

00:09:20.780 --> 00:09:23.510
The sun's energy is converted
to the chemical energy

00:09:23.510 --> 00:09:26.500
of a carbohydrate molecule
in the chloroplast.

00:09:26.500 --> 00:09:28.680
That molecule can later be broken down

00:09:28.680 --> 00:09:31.610
in most of that energy
reclaimed either by the plant

00:09:31.610 --> 00:09:33.410
or by creatures that eat that plant.

00:09:34.300 --> 00:09:37.810
All life on earth is carbon-based.

00:09:37.810 --> 00:09:40.780
And every single molecule of that carbon

00:09:40.780 --> 00:09:44.230
once existed in the
atmosphere in gaseous form

00:09:44.230 --> 00:09:47.660
as carbon dioxide until
some enterprising plant

00:09:47.660 --> 00:09:52.090
or microorganism synthesized
it into something you can use.

00:09:52.090 --> 00:09:54.910
And while they were added many
of them filled the atmosphere

00:09:54.910 --> 00:09:57.470
with the oxygen that
we all need to breathe.

00:09:57.470 --> 00:10:00.000
So the next time you see a plant,

00:10:00.000 --> 00:10:01.967
shake its leaf and say thank you.


Organization of multicellular organisms

WEBVTT
Kind: captions
Language: en

00:00:00.310 --> 00:00:01.143
- [Instructor] In this video,

00:00:01.143 --> 00:00:03.180
we're gonna take a journey in life

00:00:03.180 --> 00:00:07.150
and we're gonna start with
the smallest scale of life

00:00:07.150 --> 00:00:11.210
that is indisputably life,
and that is the cell.

00:00:11.210 --> 00:00:13.390
Now, the reason why I
qualified that a little bit

00:00:13.390 --> 00:00:16.940
is some people debate whether
viruses are living or not,

00:00:16.940 --> 00:00:18.580
'cause they have certain aspects.

00:00:18.580 --> 00:00:22.430
Viruses can reproduce, they
do have genetic information

00:00:22.430 --> 00:00:25.070
but they need other
living forms to reproduce,

00:00:25.070 --> 00:00:27.660
in particular they need other cells.

00:00:27.660 --> 00:00:29.352
But even though we imagined cells

00:00:29.352 --> 00:00:34.060
to be these very small microscopic things,

00:00:34.060 --> 00:00:37.406
they are in and of themselves
almost an entire world,

00:00:37.406 --> 00:00:39.821
and we go into depth into
that into other videos

00:00:39.821 --> 00:00:41.410
in Khan Academy.

00:00:41.410 --> 00:00:43.057
But the fact that every cell in your body,

00:00:43.057 --> 00:00:45.770
except for a few like red blood cells

00:00:45.770 --> 00:00:48.960
have all of your genetic
information in there.

00:00:48.960 --> 00:00:52.246
All of those 3 billion base pairs of DNA

00:00:52.246 --> 00:00:55.630
that make you a human being

00:00:55.630 --> 00:00:58.349
in and of itself is mind-boggling.

00:00:58.349 --> 00:01:01.460
But then the fact that
the cell specializes

00:01:01.460 --> 00:01:02.863
so that not all cells are the same

00:01:02.863 --> 00:01:05.027
even though they have that
same genetic information,

00:01:05.027 --> 00:01:08.210
they somehow know what type of cell to be

00:01:08.210 --> 00:01:10.570
that's even more interesting.

00:01:10.570 --> 00:01:13.705
So we could start at the
most basic building block

00:01:13.705 --> 00:01:16.079
in your body or really any organism's body

00:01:16.079 --> 00:01:18.860
and that's specialized cells.

00:01:18.860 --> 00:01:21.533
So what you're seeing here
is a big cluster of neurons

00:01:21.533 --> 00:01:24.190
which are dyed here in the red,

00:01:24.190 --> 00:01:27.758
and I believe these blues
show their actual nuclei

00:01:27.758 --> 00:01:30.300
where they have their genetic information.

00:01:30.300 --> 00:01:32.880
And then dyed in green,
you have what are called

00:01:32.880 --> 00:01:35.807
neuroglia cells which
are other types of cells

00:01:35.807 --> 00:01:39.870
that are inside the human brain
mainly to support neurons.

00:01:39.870 --> 00:01:42.520
Most of what we believe is thought

00:01:42.520 --> 00:01:45.170
occurs through triggering neurons,

00:01:45.170 --> 00:01:46.870
which then trigger other neurons

00:01:46.870 --> 00:01:50.290
and form cascades of these
electro-chemical signals

00:01:50.290 --> 00:01:53.400
which we're just starting to understand.

00:01:53.400 --> 00:01:57.520
But this is just one little
small fraction of a human brain.

00:01:57.520 --> 00:01:59.680
A human brain, for example we'll have

00:01:59.680 --> 00:02:04.130
on the order of 80 to 90 billion neurons.

00:02:04.130 --> 00:02:05.625
And for every one of those neurons

00:02:05.625 --> 00:02:08.740
depending on what part of the
brain you're talking about,

00:02:08.740 --> 00:02:11.870
you're talking about five
to 10 neuroglia cells.

00:02:11.870 --> 00:02:14.810
So you're talking about many
hundreds of billions of cells

00:02:14.810 --> 00:02:17.960
just in one human brain.

00:02:17.960 --> 00:02:19.990
But then if we were to
zoom out a little bit

00:02:19.990 --> 00:02:21.837
and you take a bunch of
these specialized cells

00:02:21.837 --> 00:02:25.120
working together or at
least near each other,

00:02:25.120 --> 00:02:26.623
you have tissue.

00:02:27.600 --> 00:02:31.280
And so as I said before,
this is a zoomed in view

00:02:31.280 --> 00:02:35.060
of neural tissue in
particular of brain tissue.

00:02:35.060 --> 00:02:37.710
And then if you zoom
out a little bit more,

00:02:37.710 --> 00:02:41.400
the tissue makes up organs.

00:02:41.400 --> 00:02:44.770
And if we're thinking about
neural tissue like this,

00:02:44.770 --> 00:02:47.680
we can imagine that it makes up the brain

00:02:47.680 --> 00:02:49.660
which is an organ.

00:02:49.660 --> 00:02:53.930
And then organs build up to systems.

00:02:53.930 --> 00:02:56.410
And right over here, you have a picture

00:02:56.410 --> 00:02:59.620
of the nervous system of
which the brain is apart.

00:02:59.620 --> 00:03:00.453
You also have the spinal cord,

00:03:00.453 --> 00:03:01.936
and then you also have all of the nerves

00:03:01.936 --> 00:03:03.660
that go throughout the body.

00:03:03.660 --> 00:03:05.713
So we have a system.

00:03:06.580 --> 00:03:09.170
And then you put all
of the systems together

00:03:09.170 --> 00:03:13.060
and you get the actual organism,

00:03:13.060 --> 00:03:16.470
which of course you can somewhat
visualize right over here

00:03:16.470 --> 00:03:18.290
where you can see all of
these different organs

00:03:18.290 --> 00:03:22.150
and organ systems put
together to create who we are.

00:03:22.150 --> 00:03:24.796
And just to connect to the
organism with the cells,

00:03:24.796 --> 00:03:27.460
that basic building block of life.

00:03:27.460 --> 00:03:30.210
If you are a average size human being,

00:03:30.210 --> 00:03:35.210
you likely have 30 to 40
trillion cells in your body.

00:03:35.910 --> 00:03:37.570
And if that isn't mind blowing enough

00:03:37.570 --> 00:03:38.910
and it is just an estimate,

00:03:38.910 --> 00:03:40.460
it's estimated that there's as many

00:03:40.460 --> 00:03:45.190
as 100 trillion bacteria in your body.

00:03:45.190 --> 00:03:49.500
And so even though you think
you are just "an individual"

00:03:49.500 --> 00:03:51.532
you are a universe of living things

00:03:51.532 --> 00:03:53.430
in these complex systems.

00:03:53.430 --> 00:03:55.560
And it's an interesting question of why

00:03:55.560 --> 00:03:56.930
and right over here.

00:03:56.930 --> 00:03:59.410
We know that organisms
interact with each other.

00:03:59.410 --> 00:04:01.810
We know that they interact
with their environment

00:04:01.810 --> 00:04:04.211
just as each of our nerve
cells might not appreciate

00:04:04.211 --> 00:04:08.350
that they are one of 86
billion in dissension mind,

00:04:08.350 --> 00:04:11.710
maybe we ourselves as
organisms don't appreciate

00:04:11.710 --> 00:04:13.620
that we too are building blocks

00:04:13.620 --> 00:04:15.553
of maybe something even larger.


Genes, proteins, and cells

WEBVTT
Kind: captions
Language: en

00:00:00.500 --> 00:00:02.010
- [Instructor] So when I was younger,

00:00:02.010 --> 00:00:03.550
around seven or eight years old,

00:00:03.550 --> 00:00:06.450
I used to have a beta fish named Bob,

00:00:06.450 --> 00:00:09.670
and he happened to be a blue-colored fish.

00:00:09.670 --> 00:00:12.670
Now, I've always wondered
how he got his color.

00:00:12.670 --> 00:00:15.940
So for example, were
his parents also blue?

00:00:15.940 --> 00:00:18.440
Does he have any siblings that were blue?

00:00:18.440 --> 00:00:21.530
So today, let's try to
answer in simple terms

00:00:21.530 --> 00:00:24.430
how Bob gets his blue color.

00:00:24.430 --> 00:00:27.030
And we'll start by defining genes.

00:00:27.030 --> 00:00:30.040
Genes. What are genes?

00:00:30.040 --> 00:00:33.140
Well, genes are basic hereditary units

00:00:33.140 --> 00:00:34.620
that are well, first of all,

00:00:34.620 --> 00:00:37.110
they are passed down
from parent to offspring.

00:00:37.110 --> 00:00:41.530
So I'll write passed
down parent to offspring.

00:00:41.530 --> 00:00:43.690
And they also contain information

00:00:43.690 --> 00:00:46.220
about an organism's traits.

00:00:46.220 --> 00:00:51.220
Contain info about an organism's traits.

00:00:51.310 --> 00:00:53.810
So it would only make sense that since Bob

00:00:53.810 --> 00:00:57.260
is a blue-colored fish,
that he must have a parent

00:00:57.260 --> 00:01:00.300
or ancestor who is also blue-colored.

00:01:00.300 --> 00:01:03.920
Now, a single kind of gene can
have many different versions,

00:01:03.920 --> 00:01:07.030
and we call these versions alleles.

00:01:07.030 --> 00:01:08.420
Alleles.

00:01:08.420 --> 00:01:11.823
And these are just different
variations of a single gene.

00:01:12.720 --> 00:01:14.460
So for example, there may be a gene

00:01:14.460 --> 00:01:17.930
that provides information
about beta fish coloration.

00:01:17.930 --> 00:01:22.930
So let me draw an arrow from
Bob to, we'll say, color gene.

00:01:23.500 --> 00:01:28.500
And one allele of this gene may
lead to a blue-colored fish.

00:01:29.110 --> 00:01:32.910
So I'll write here blue color.

00:01:32.910 --> 00:01:36.950
And another allele may
lead to green coloration.

00:01:36.950 --> 00:01:41.530
And I'll write here, next
to blue color, green color.

00:01:41.530 --> 00:01:44.790
But physically, what are genes, exactly?

00:01:44.790 --> 00:01:49.410
Well, genes are part of DNA
or deoxyribonucleic acid.

00:01:49.410 --> 00:01:51.110
And I know, it's a really big word.

00:01:51.110 --> 00:01:53.060
So let me write it out for us.

00:01:53.060 --> 00:01:57.120
DNA. Deoxyribonucleic acid.

00:01:57.120 --> 00:01:57.953
DNA.

00:01:59.550 --> 00:02:02.220
So DNA is a macromolecule,

00:02:02.220 --> 00:02:05.980
or a really big and complex molecule.

00:02:05.980 --> 00:02:10.760
So when you hear macro, just
think big or complex molecule.

00:02:10.760 --> 00:02:14.530
And you can also think of
DNA like a giant cookbook

00:02:14.530 --> 00:02:17.890
of genetic information,
because that's what it is.

00:02:17.890 --> 00:02:21.473
It is a cookbook of genetic information.

00:02:23.230 --> 00:02:25.890
So here is a close-up sketch of DNA.

00:02:25.890 --> 00:02:29.220
And what I'm showing
here is that DNA consists

00:02:29.220 --> 00:02:32.530
of subunits called nucleotides.

00:02:32.530 --> 00:02:33.930
Nucleotides.

00:02:33.930 --> 00:02:38.930
And these are represented
by As, Ts, Cs, and Gs.

00:02:40.860 --> 00:02:43.810
Now genes are like the individual recipes.

00:02:43.810 --> 00:02:46.390
You can think of them as the recipes found

00:02:46.390 --> 00:02:48.700
inside your DNA cookbook.

00:02:48.700 --> 00:02:51.420
So they are specific
segments of nucleotides

00:02:51.420 --> 00:02:54.090
within the long DNA molecule.

00:02:54.090 --> 00:02:57.350
So a gene could be from here to here.

00:02:57.350 --> 00:03:00.970
And we think of this as a recipe.

00:03:00.970 --> 00:03:03.920
But what do these gene
recipes make anyways?

00:03:03.920 --> 00:03:06.690
Well, many genes encode proteins,

00:03:06.690 --> 00:03:09.330
which are made of long sequences

00:03:09.330 --> 00:03:11.710
or chains of amino acids.

00:03:11.710 --> 00:03:13.520
So, I'll write here under proteins

00:03:13.520 --> 00:03:17.620
that proteins are made
of amino acid chains.

00:03:17.620 --> 00:03:19.430
And genes provide instructions

00:03:19.430 --> 00:03:21.370
for how to create these chains.

00:03:21.370 --> 00:03:24.770
So thinking back to how
genes are like recipes

00:03:24.770 --> 00:03:27.030
because each gene has a different set

00:03:27.030 --> 00:03:30.440
of quote-unquote,
"ingredients", or in this case,

00:03:30.440 --> 00:03:32.450
a different nucleotide sequence,

00:03:32.450 --> 00:03:36.500
different genes would therefore
encode different proteins.

00:03:36.500 --> 00:03:38.050
So proteins in this example,

00:03:38.050 --> 00:03:40.630
if you want to continue
on with this analogy,

00:03:40.630 --> 00:03:42.650
proteins would be like
the finished products

00:03:42.650 --> 00:03:44.030
of your recipes.

00:03:44.030 --> 00:03:46.410
Remember how I mentioned that alleles

00:03:46.410 --> 00:03:49.500
are different versions of a specific gene?

00:03:49.500 --> 00:03:53.020
Well, different alleles have
different nucleotide sequences

00:03:53.020 --> 00:03:57.740
and are therefore likely to
also encode different proteins.

00:03:57.740 --> 00:03:59.980
So I'll write under
here, different alleles,

00:03:59.980 --> 00:04:02.820
and draw an arrow to different proteins.

00:04:02.820 --> 00:04:05.300
So different genes and different alleles

00:04:05.300 --> 00:04:07.680
can give us different proteins.

00:04:07.680 --> 00:04:11.370
So of blue fish like Bob,
likely has a distinct allele

00:04:11.370 --> 00:04:15.460
that encodes proteins, which
give him his natural blue color

00:04:15.460 --> 00:04:17.260
or his natural blue shade.

00:04:17.260 --> 00:04:20.230
Now, an organism has many different genes,

00:04:20.230 --> 00:04:23.010
which means an organism has the capacity

00:04:23.010 --> 00:04:25.920
to produce many different
kinds of proteins.

00:04:25.920 --> 00:04:28.800
And proteins serve all kinds of functions,

00:04:28.800 --> 00:04:33.600
some of which include
growth, sending messages,

00:04:33.600 --> 00:04:36.210
oh, also catalyzing chemical reactions,

00:04:36.210 --> 00:04:38.440
if you have heard of enzymes before.

00:04:38.440 --> 00:04:41.640
So, I'll write catalyzing
chemical reactions

00:04:42.650 --> 00:04:44.303
and providing structure.

00:04:45.430 --> 00:04:47.270
Ultimately, it's the activity

00:04:47.270 --> 00:04:49.440
of these different kinds of proteins

00:04:49.440 --> 00:04:52.320
that help determine an
organism's physical traits,

00:04:52.320 --> 00:04:54.680
just like how proteins can determine

00:04:54.680 --> 00:04:56.883
the color of Bob the beta fish.

00:04:57.810 --> 00:04:59.190
Now, you might be wondering too,

00:04:59.190 --> 00:05:01.760
what genes do in the big picture.

00:05:01.760 --> 00:05:04.930
For example, not all of the
cells in Bob the beta fish

00:05:04.930 --> 00:05:06.670
function in the same way, right?

00:05:06.670 --> 00:05:08.660
You could say that there
are different types

00:05:08.660 --> 00:05:11.600
of cells that perform specific functions.

00:05:11.600 --> 00:05:14.830
And this is known as cell specialization.

00:05:14.830 --> 00:05:18.560
So cell specialization is when
different cells specialize

00:05:18.560 --> 00:05:20.290
in different functions.

00:05:20.290 --> 00:05:22.160
And each type of specialized cell

00:05:22.160 --> 00:05:25.430
contains a unique combination of proteins

00:05:25.430 --> 00:05:27.910
that give the cell its
specialized function

00:05:27.910 --> 00:05:29.140
within an organism.

00:05:29.140 --> 00:05:31.930
So I'll write here that
cell specialization

00:05:31.930 --> 00:05:35.260
comes from unique combos of proteins.

00:05:35.260 --> 00:05:36.640
And it's important to note

00:05:36.640 --> 00:05:40.640
that every cell in an organism
contains the same genes.

00:05:40.640 --> 00:05:41.970
So going back to Bob here,

00:05:41.970 --> 00:05:44.530
we can say that all his cells contain

00:05:44.530 --> 00:05:47.210
the same DNA and genetic information,

00:05:47.210 --> 00:05:50.740
whether it's on his tail or in his eye,

00:05:50.740 --> 00:05:52.470
but what makes their functions different

00:05:52.470 --> 00:05:55.350
is which subset of genes are expressed

00:05:55.350 --> 00:05:59.460
or used to build proteins
in the different cell types.

00:05:59.460 --> 00:06:03.360
So, I'll write here, all of
the cells in Bob the beta fish

00:06:03.360 --> 00:06:06.280
have the same DNA and genes,

00:06:06.280 --> 00:06:09.163
just different protein combinations.

00:06:10.070 --> 00:06:13.100
So today, we learned about
genes which are passed down

00:06:13.100 --> 00:06:14.440
from parent to offspring,

00:06:14.440 --> 00:06:18.230
just like how Bob the blue
beta fish got his color,

00:06:18.230 --> 00:06:21.950
and they contain information
about organisms' traits.

00:06:21.950 --> 00:06:24.890
So genes are parts of longer DNA molecules

00:06:24.890 --> 00:06:28.980
and they consist of specific
segments of nucleotide bases.

00:06:28.980 --> 00:06:33.520
So thinking back to our cookbook
and recipe analogy, right?

00:06:33.520 --> 00:06:36.780
Genes can encode all kinds
of different proteins.

00:06:36.780 --> 00:06:39.150
And it's this unique set of proteins

00:06:39.150 --> 00:06:42.370
within each cell that gives
the cell its specific function

00:06:42.370 --> 00:06:43.500
within the organism.

00:06:43.500 --> 00:06:46.490
As we talked about with Bob the beta fish,

00:06:46.490 --> 00:06:50.330
and all of the cells in Bob
having the same DNA and genes,

00:06:50.330 --> 00:06:51.873
just different proteins.


Greenhouse effect and greenhouse gases

WEBVTT
Kind: captions
Language: en

00:00:00.370 --> 00:00:01.203
- [Instructor] In this video,

00:00:01.203 --> 00:00:04.400
we're gonna talk about
the greenhouse effect

00:00:04.400 --> 00:00:06.790
and also the greenhouse gases,

00:00:06.790 --> 00:00:09.680
which cause the greenhouse effect.

00:00:09.680 --> 00:00:12.070
Now let's just start with a basic idea.

00:00:12.070 --> 00:00:15.880
Imagine if earth had no
atmosphere, what would happen?

00:00:15.880 --> 00:00:16.880
Well, you have the sun,

00:00:16.880 --> 00:00:20.130
which is on average,
93 million miles away.

00:00:20.130 --> 00:00:22.700
It's sending electromagnetic radiation

00:00:22.700 --> 00:00:24.750
our way to the surface of the earth.

00:00:24.750 --> 00:00:27.080
We're actually getting a
very, very small fraction

00:00:27.080 --> 00:00:30.570
of the total electromagnetic
radiation of the sun.

00:00:30.570 --> 00:00:33.570
And then that would heat up
the surface of the earth.

00:00:33.570 --> 00:00:36.330
Now, what I have always found mind-blowing

00:00:36.330 --> 00:00:38.330
is anything with temperature

00:00:38.330 --> 00:00:40.850
will emit electromagnetic radiation.

00:00:40.850 --> 00:00:42.950
And so it's emitting some of that energy,

00:00:42.950 --> 00:00:44.930
it's losing some of that energy

00:00:44.930 --> 00:00:47.320
to electromagnetic radiation.

00:00:47.320 --> 00:00:50.750
So the surface would be releasing that

00:00:50.750 --> 00:00:53.950
and it would go out into space.

00:00:53.950 --> 00:00:57.450
But now let's introduce
the idea of an atmosphere.

00:00:57.450 --> 00:00:58.930
And in particular, we're gonna think

00:00:58.930 --> 00:01:00.403
about our lower atmosphere,

00:01:00.403 --> 00:01:02.760
which starts at the surface and goes up

00:01:02.760 --> 00:01:05.160
to about five to nine miles in altitude,

00:01:05.160 --> 00:01:07.282
often known as the troposphere.

00:01:07.282 --> 00:01:10.840
Now the troposphere has molecules in it,

00:01:10.840 --> 00:01:14.030
has gases in it like carbon dioxide,

00:01:14.030 --> 00:01:17.140
like water vapor, like methane.

00:01:17.140 --> 00:01:21.320
Others include nitrous oxide
and chlorofluorocarbons.

00:01:21.320 --> 00:01:22.990
You don't have to know
the chemical formula

00:01:22.990 --> 00:01:24.240
of all of these things,

00:01:24.240 --> 00:01:27.310
but what's interesting about these gases

00:01:27.310 --> 00:01:31.230
that are in the lower atmosphere
is that they can absorb

00:01:31.230 --> 00:01:33.410
some of those electromagnetic waves

00:01:33.410 --> 00:01:35.680
that the surface of the earth is emitting.

00:01:35.680 --> 00:01:38.130
So some of that energy
will make it out to space,

00:01:38.130 --> 00:01:40.740
but some of that energy
will then be absorbed

00:01:40.740 --> 00:01:43.020
by these molecules, by these gases,

00:01:43.020 --> 00:01:45.850
and then they will emit
some of that back to earth.

00:01:45.850 --> 00:01:48.150
And so that's why it's
called a greenhouse effect

00:01:48.150 --> 00:01:49.550
because of all of that energy

00:01:49.550 --> 00:01:51.510
that might have been sent out to space

00:01:51.510 --> 00:01:54.590
if you didn't have an
atmosphere, not all of it is.

00:01:54.590 --> 00:01:57.080
Some of it is reabsorbed
by the atmosphere,

00:01:57.080 --> 00:01:59.610
which then sends it
back down to the surface

00:01:59.610 --> 00:02:01.750
and that process can go on and on and on.

00:02:01.750 --> 00:02:05.930
You can imagine that it's
trapping some of the energy.

00:02:05.930 --> 00:02:09.280
Now, the greenhouse effect
and greenhouse gases,

00:02:09.280 --> 00:02:12.088
the ones that I just listed,
they're oftentimes associated

00:02:12.088 --> 00:02:15.550
with man-made climate
change and global warming.

00:02:15.550 --> 00:02:17.720
And they are, for good reason,

00:02:17.720 --> 00:02:18.920
but it's important to realize

00:02:18.920 --> 00:02:22.570
that we actually need some
base level greenhouse effect

00:02:22.570 --> 00:02:25.870
just for earth to be habitable
in the way that it is.

00:02:25.870 --> 00:02:29.080
Without greenhouse gases, earth's surface

00:02:29.080 --> 00:02:32.730
would be about negative
18 degrees Celsius,

00:02:32.730 --> 00:02:35.326
which is the same as
zero degrees Fahrenheit,

00:02:35.326 --> 00:02:37.225
which I think most of
y'all would recognize

00:02:37.225 --> 00:02:39.920
is very, very, very cold

00:02:39.920 --> 00:02:42.940
relative to what the actual averages are,

00:02:42.940 --> 00:02:47.940
which are 15 degrees Celsius
or 59 degrees Fahrenheit.

00:02:48.920 --> 00:02:50.570
And of course, these are
average temperatures,

00:02:50.570 --> 00:02:53.291
but 59 is a nice refreshing brisk day,

00:02:53.291 --> 00:02:56.870
not a frigid day like
zero degrees Fahrenheit.

00:02:56.870 --> 00:02:57.930
And of course, these are averages.

00:02:57.930 --> 00:03:01.920
It fluctuates around this on
time of year and where you are.

00:03:01.920 --> 00:03:02.900
But this has makes it clear

00:03:02.900 --> 00:03:05.270
that we do need these greenhouse gases

00:03:05.270 --> 00:03:07.920
to keep the earth reasonably warm.

00:03:07.920 --> 00:03:09.020
Now, the problem is,

00:03:09.020 --> 00:03:11.660
is if the concentration
of these greenhouse gases

00:03:11.660 --> 00:03:15.490
go out of equilibrium,
become unusually high,

00:03:15.490 --> 00:03:18.860
and it does look like
that is indeed happening.

00:03:18.860 --> 00:03:20.639
This right over here is a chart,

00:03:20.639 --> 00:03:22.750
and the way that we're
able to figure that out

00:03:22.750 --> 00:03:25.340
is by taking ice samples and rock samples

00:03:25.340 --> 00:03:27.980
and looking into our past
or the geologic record

00:03:27.980 --> 00:03:30.020
of how much carbon dioxide there has been

00:03:30.020 --> 00:03:31.990
over the last 800,000 years.

00:03:31.990 --> 00:03:35.210
And 800,000 years is a
very long time period.

00:03:35.210 --> 00:03:37.100
Modern human beings have only been around

00:03:37.100 --> 00:03:40.090
for 200,000 or 300,000 years.

00:03:40.090 --> 00:03:43.370
And what you can see is the
concentration of carbon dioxide

00:03:43.370 --> 00:03:46.870
has roughly fluctuated between
about 200 parts per million

00:03:46.870 --> 00:03:48.880
and about 300 parts per million,

00:03:48.880 --> 00:03:51.290
at least over the duration of this chart.

00:03:51.290 --> 00:03:54.240
But in recent times, we've
gone well beyond that.

00:03:54.240 --> 00:03:57.810
We've almost gone double
that average right over here.

00:03:57.810 --> 00:03:59.319
And this is actually the highest levels

00:03:59.319 --> 00:04:03.430
we've seen in three million years.

00:04:03.430 --> 00:04:05.920
That's important to
realize that carbon dioxide

00:04:05.920 --> 00:04:08.760
makes up a small percentage
of our atmosphere.

00:04:08.760 --> 00:04:10.220
In fact, all of these greenhouse gases

00:04:10.220 --> 00:04:12.090
make up a small percentage.

00:04:12.090 --> 00:04:16.510
78% of the troposphere is
in nitrogen, 21% is oxygen.

00:04:16.510 --> 00:04:19.740
The last 1% is things like argon,

00:04:19.740 --> 00:04:23.130
water vapor, carbon dioxide, methane.

00:04:23.130 --> 00:04:25.050
So even this small amount,

00:04:25.050 --> 00:04:27.540
when the concentration
increases dramatically

00:04:27.540 --> 00:04:29.300
can have a huge effect.

00:04:29.300 --> 00:04:31.630
Now you might say, "Hey,
we were at these levels

00:04:31.630 --> 00:04:34.120
three million years ago roughly,

00:04:34.120 --> 00:04:36.696
maybe this is just some type of cycle

00:04:36.696 --> 00:04:38.780
that we're seeing on earth."

00:04:38.780 --> 00:04:41.720
And to recognize it,
this is indeed manmade,

00:04:41.720 --> 00:04:44.170
we just have to look at a chart like this.

00:04:44.170 --> 00:04:45.940
This tells us two things.

00:04:45.940 --> 00:04:48.850
This tells us annual
emissions in this blue line,

00:04:48.850 --> 00:04:51.660
this blue curve, and
then the total emission

00:04:51.660 --> 00:04:53.920
or the total concentration
in the atmosphere,

00:04:53.920 --> 00:04:56.870
because about one of the
things about greenhouse gas

00:04:56.870 --> 00:04:58.780
like carbon dioxide, when it's emitted,

00:04:58.780 --> 00:05:00.360
it doesn't just disappear.

00:05:00.360 --> 00:05:02.907
And we can see if we go to
the pre-industrial revolution

00:05:02.907 --> 00:05:05.910
or the early stages of
the industrial revolution,

00:05:05.910 --> 00:05:09.770
CO2 emissions were pretty
low, pretty close to zero,

00:05:09.770 --> 00:05:11.660
at least on this scale right over here.

00:05:11.660 --> 00:05:14.030
There might've been some
basic CO2 emissions,

00:05:14.030 --> 00:05:16.750
people had fires and stoves
and things like that.

00:05:16.750 --> 00:05:19.070
But then as the industrial
revolution came into play

00:05:19.070 --> 00:05:21.440
and we started using
fossil fuels more and more

00:05:21.440 --> 00:05:24.610
to fuel transportation and
factories and other things,

00:05:24.610 --> 00:05:26.460
our emissions have gone up dramatically.

00:05:26.460 --> 00:05:28.870
And this coincides with
the total concentration

00:05:28.870 --> 00:05:33.180
going well above that
800,000 year average.

00:05:33.180 --> 00:05:35.900
So it's important to keep in
mind, the greenhouse effect

00:05:35.900 --> 00:05:38.870
is needed to some degree,
but the problem is,

00:05:38.870 --> 00:05:41.130
is when the concentration
of greenhouse gases

00:05:41.130 --> 00:05:44.950
like carbon dioxide go well
beyond their historic averages,

00:05:44.950 --> 00:05:46.880
which can over time warm the earth

00:05:46.880 --> 00:05:50.230
and even a few degrees
centigrade of warming the earth

00:05:50.230 --> 00:05:52.940
can have huge consequences
on our environment

00:05:52.940 --> 00:05:54.400
and on our weather.

00:05:54.400 --> 00:05:56.830
I'll throw out one last
idea just for kicks

00:05:56.830 --> 00:05:59.180
because even though it's
called the greenhouse effect,

00:05:59.180 --> 00:06:01.990
it's actually not how
actual greenhouses work.

00:06:01.990 --> 00:06:04.400
The greenhouse effect,
as we just described it,

00:06:04.400 --> 00:06:07.526
is really based on this idea that things

00:06:07.526 --> 00:06:09.950
are getting the infrared radiation.

00:06:09.950 --> 00:06:12.610
The electromagnetic radiation
is getting reabsorbed,

00:06:12.610 --> 00:06:15.440
which then gets reemitted
back to the surface

00:06:15.440 --> 00:06:16.630
and vice right versa.

00:06:16.630 --> 00:06:17.640
In a real greenhouse,

00:06:17.640 --> 00:06:20.640
you can imagine that it
is made out of glass.

00:06:20.640 --> 00:06:24.030
What's happening is the
sunlight can come in

00:06:24.030 --> 00:06:25.720
and it's warming the surface

00:06:25.720 --> 00:06:29.260
and it's warming the air
inside the greenhouse,

00:06:29.260 --> 00:06:32.180
and then that air is not
allowed to circulate.

00:06:32.180 --> 00:06:34.880
So if the greenhouse had a little hole

00:06:34.880 --> 00:06:36.070
at the top right over here,

00:06:36.070 --> 00:06:38.040
that hot air would be allowed to go out

00:06:38.040 --> 00:06:40.530
and circulate with the cool air up here,

00:06:40.530 --> 00:06:42.420
but the air isn't allowed to mix,

00:06:42.420 --> 00:06:44.920
and so the air gets hotter
and hotter and hotter.

00:06:44.920 --> 00:06:46.590
It actually turns out that the glass

00:06:46.590 --> 00:06:49.220
can let the electromagnetic radiation out

00:06:49.220 --> 00:06:51.470
unlike greenhouse gases.

00:06:51.470 --> 00:06:54.890
So it is a different
actual physical process,

00:06:54.890 --> 00:06:57.793
but you can see where people
try to create the metaphor.


Cell specialization

WEBVTT
Kind: captions
Language: en

00:00:02.040 --> 00:00:04.080
- [Instructor] Ah, the
basic building blocks

00:00:04.080 --> 00:00:06.823
of all living things, cells.

00:00:09.620 --> 00:00:12.040
These incredible packages of organelles

00:00:12.040 --> 00:00:13.940
and subcellular components

00:00:13.940 --> 00:00:17.030
carry out a variety of
functions in the body,

00:00:17.030 --> 00:00:19.003
like taking in nutrients,

00:00:20.950 --> 00:00:22.823
converting them into energy,

00:00:24.540 --> 00:00:27.040
and working with other
cells to produce things

00:00:27.040 --> 00:00:28.223
that the body needs.

00:00:29.550 --> 00:00:33.253
Each cell is essentially like
its own little mini factory,

00:00:34.270 --> 00:00:36.860
with complex processes
occurring within the cell

00:00:36.860 --> 00:00:38.623
to carry out specific functions.

00:00:39.790 --> 00:00:43.170
Okay, so when we zoom into
the cell to figure out

00:00:43.170 --> 00:00:46.690
how exactly these cell
processes are carried out,

00:00:46.690 --> 00:00:48.260
one of the star players

00:00:48.260 --> 00:00:53.133
is a class of biological
macromolecules known as proteins.

00:00:57.910 --> 00:00:58.810
Proteins carry out

00:00:58.810 --> 00:01:01.660
many incredibly important
tasks in the cell,

00:01:01.660 --> 00:01:05.110
such as providing structural support,

00:01:05.110 --> 00:01:07.490
aiding in chemical reactions

00:01:10.730 --> 00:01:13.283
and even building or repairing the cell.

00:01:16.020 --> 00:01:20.600
We can imagine proteins
as a chain of amino acids,

00:01:20.600 --> 00:01:23.800
kind of think of them as
like beads on a bracelet

00:01:24.870 --> 00:01:29.870
that fold and twist into distinct
three-dimensional shapes.

00:01:31.370 --> 00:01:33.490
The structure of a protein

00:01:34.610 --> 00:01:38.670
along with the chemical
properties of its amino acid,

00:01:38.670 --> 00:01:40.623
evidently, determine its function.

00:01:45.290 --> 00:01:47.950
Does it form a round, globular sphere

00:01:47.950 --> 00:01:51.080
that can attach and interact
with other compounds?

00:01:51.080 --> 00:01:54.320
Or does it twist into
long and narrow strands

00:01:54.320 --> 00:01:56.343
that can provide structural support?

00:01:57.230 --> 00:01:59.600
The huge variety of structures

00:01:59.600 --> 00:02:01.450
that proteins can take on

00:02:01.450 --> 00:02:03.850
leads to the wide range
of cellular functions

00:02:03.850 --> 00:02:05.050
that they can carry out.

00:02:06.330 --> 00:02:09.050
Okay, so now that we've
talked about proteins,

00:02:09.050 --> 00:02:10.640
let's zoom back out

00:02:10.640 --> 00:02:13.780
to analyze how different
types of cells come together

00:02:13.780 --> 00:02:17.013
to carry out a variety of
functions in an organism.

00:02:18.420 --> 00:02:21.903
This is where cell
specialization comes into play,

00:02:25.290 --> 00:02:28.700
which is the process by
which a cell takes on

00:02:28.700 --> 00:02:31.620
a specific structure and function.

00:02:31.620 --> 00:02:34.610
So to better help understand this concept,

00:02:34.610 --> 00:02:37.730
let's consider a movie theater analogy

00:02:37.730 --> 00:02:40.900
where the movie theater is your body.

00:02:40.900 --> 00:02:44.870
There is the cashier that
handles all the money,

00:02:44.870 --> 00:02:49.870
the snack vendor who handles
out popcorn and snacks

00:02:49.950 --> 00:02:51.870
and even the ticket operator

00:02:51.870 --> 00:02:54.590
who directs you to the proper screenings.

00:02:54.590 --> 00:02:55.870
In this analogy,

00:02:55.870 --> 00:02:59.370
each person has their
own distinct functions

00:02:59.370 --> 00:03:00.400
in what they handle,

00:03:00.400 --> 00:03:03.660
like money or popcorn or tickets.

00:03:03.660 --> 00:03:04.890
In a similar way,

00:03:04.890 --> 00:03:07.860
the body is also composed
of specialized cells

00:03:07.860 --> 00:03:09.023
with unique roles,

00:03:10.530 --> 00:03:14.823
such as red blood cells that
carry oxygen in the blood,

00:03:16.330 --> 00:03:20.230
muscle cells that contract and relax

00:03:20.230 --> 00:03:24.130
or even nerve cells that
carry signaling messages

00:03:24.130 --> 00:03:25.130
throughout the body.

00:03:26.170 --> 00:03:29.863
Now, remember how I told
you about proteins before?

00:03:30.810 --> 00:03:33.630
Well, cell specialization is largely based

00:03:33.630 --> 00:03:38.630
on which proteins are present
or absent in the cell.

00:03:40.410 --> 00:03:44.350
It is a cell's unique
combination of proteins

00:03:46.250 --> 00:03:48.750
that determine which
functions can be carried out.

00:03:52.900 --> 00:03:54.930
But no cell works alone,

00:03:54.930 --> 00:03:57.363
because teamwork makes the dream work.

00:03:58.470 --> 00:04:00.740
Groups of specialized cells

00:04:02.660 --> 00:04:05.820
that carry out specific
functions for the organism

00:04:05.820 --> 00:04:08.053
are organized into tissues.

00:04:11.890 --> 00:04:15.220
Looking back at our movie theater analogy,

00:04:15.220 --> 00:04:18.360
there are multiple people
within each department

00:04:18.360 --> 00:04:21.713
that work together to help the
theater function efficiently.

00:04:22.990 --> 00:04:26.020
Similarly, our specialized
cells work together

00:04:26.020 --> 00:04:28.903
as tissues to help the organism function.

00:04:29.810 --> 00:04:32.733
The red blood cells make up the blood,

00:04:33.930 --> 00:04:34.930
a connective tissue

00:04:34.930 --> 00:04:37.770
that moves important
substances throughout the body.

00:04:37.770 --> 00:04:40.750
The muscle cells help
make up muscle tissue

00:04:43.180 --> 00:04:44.790
which helps the body move

00:04:44.790 --> 00:04:48.440
and neurons or nerve cells
make up nervous tissue

00:04:50.220 --> 00:04:52.653
that helps the organism
process information.

00:04:53.610 --> 00:04:57.910
So what are the key takeaways
about cell specialization?

00:04:57.910 --> 00:05:02.010
Number one, cells are the
fundamental unit of life.

00:05:02.010 --> 00:05:03.520
They're the smallest structural

00:05:03.520 --> 00:05:06.370
and functional unit of an organism.

00:05:06.370 --> 00:05:11.170
Number two, proteins help
carry out cell processes.

00:05:11.170 --> 00:05:13.810
Number three, specialized cells carry out

00:05:13.810 --> 00:05:16.160
specific functions in an organism.

00:05:16.160 --> 00:05:18.020
Think of the movie theater analogy

00:05:18.020 --> 00:05:21.490
where each person has
its own specific role.

00:05:21.490 --> 00:05:24.270
And number four, groups
of specialized cells

00:05:24.270 --> 00:05:25.900
come together as tissues

00:05:25.900 --> 00:05:28.120
to carry out one or
more specific functions

00:05:28.120 --> 00:05:29.083
for the organism.


Taking and visualizing powers of a complex number

WEBVTT
Kind: captions
Language: en

00:00:00.450 --> 00:00:02.940
- We're told to consider the
complex number z is equal

00:00:02.940 --> 00:00:05.950
to -1 plus i times the square root of 3.

00:00:05.950 --> 00:00:09.500
Find z to the fourth in
polar and rectangular form.

00:00:09.500 --> 00:00:12.250
So pause this video and see
if you can figure that out.

00:00:13.090 --> 00:00:14.910
All right, now let's work
through this together.

00:00:14.910 --> 00:00:19.320
So first let's just think
about what the modulus of z is.

00:00:19.320 --> 00:00:22.240
We know that the modulus
is going to be equal to the

00:00:22.240 --> 00:00:25.480
square root of the real part squared

00:00:25.480 --> 00:00:28.940
plus the square root of 3, plus
the imaginary part squared.

00:00:28.940 --> 00:00:33.040
So it is going to be -1 squared

00:00:33.040 --> 00:00:36.800
plus square root of 3 squared,

00:00:36.800 --> 00:00:39.400
which is going to be equal to 1 plus 3.

00:00:39.400 --> 00:00:43.300
So principal root of
4, which is equal to 2.

00:00:43.300 --> 00:00:44.910
Now the next interesting question is,

00:00:44.910 --> 00:00:47.540
what is the argument of z?

00:00:47.540 --> 00:00:49.300
And the reason why I'm
even going through this is

00:00:49.300 --> 00:00:50.850
once we put it into polar form,

00:00:50.850 --> 00:00:53.720
it's going to be a lot
easier to both visualize

00:00:53.720 --> 00:00:56.640
what it means to take the
various exponents of it.

00:00:56.640 --> 00:00:59.850
And then we can convert
back into rectangular form.

00:00:59.850 --> 00:01:04.850
And so let us, let me draw
another complex plane here.

00:01:05.790 --> 00:01:07.130
Imaginary axis.

00:01:07.130 --> 00:01:10.410
That is my real axis.

00:01:10.410 --> 00:01:14.100
And if I were to plot z, it
would look something like this.

00:01:14.100 --> 00:01:16.160
We have -1 in the real direction.

00:01:16.160 --> 00:01:18.530
So that might be -1 there.

00:01:18.530 --> 00:01:22.940
And we have square root of 3
in the imaginary direction,

00:01:22.940 --> 00:01:24.120
square root of 3.

00:01:24.120 --> 00:01:27.950
So our point z is right over here

00:01:27.950 --> 00:01:32.090
and we know the distance
from the origin, the modulus,

00:01:32.090 --> 00:01:35.630
we know that this distance
right over here is 2.

00:01:35.630 --> 00:01:38.050
We know that this distance right over here

00:01:38.050 --> 00:01:40.000
is square root of 3.

00:01:40.000 --> 00:01:44.540
And we know that this
distance right over here is 1.

00:01:44.540 --> 00:01:46.650
And so you might
immediately recognize this

00:01:46.650 --> 00:01:50.470
as a 30-60-90 triangle because
in a 30-60-90 triangle,

00:01:50.470 --> 00:01:53.680
the short side is half of the hypotenuse,

00:01:53.680 --> 00:01:55.840
and the long side is the square root of 3

00:01:55.840 --> 00:01:57.400
times the short side.

00:01:57.400 --> 00:02:00.450
So we know that this is a 60-degree angle.

00:02:00.450 --> 00:02:02.820
We know that this is a 30-degree angle.

00:02:02.820 --> 00:02:04.460
And the reason why that helps us,

00:02:04.460 --> 00:02:06.340
sorry, it's hard to see that 30 degree.

00:02:06.340 --> 00:02:07.830
The reason why that helps us is

00:02:07.830 --> 00:02:09.540
if this is 60 degrees,

00:02:09.540 --> 00:02:14.540
we know that the argument
here must be 120 degrees.

00:02:14.970 --> 00:02:19.610
So the arg of z, the argument
of z, is 120 degrees.

00:02:19.610 --> 00:02:20.880
And so just like that

00:02:20.880 --> 00:02:24.210
we can now think about z in polar form.

00:02:24.210 --> 00:02:26.360
So let me write it right over here.

00:02:26.360 --> 00:02:31.360
We can write that z is
equal to its modulus, 2,

00:02:31.370 --> 00:02:34.153
times the cosine of 120 degrees,

00:02:36.486 --> 00:02:39.569
plus i times the sine of 120 degrees.

00:02:41.660 --> 00:02:44.990
And we could also
visualize z now over here.

00:02:44.990 --> 00:02:48.030
So its modulus is 2.

00:02:48.030 --> 00:02:53.030
So that's halfway to 4, and
its argument is 120 degrees.

00:02:53.820 --> 00:02:56.450
So it would put us right over here.

00:02:56.450 --> 00:03:00.140
This is where z is.

00:03:00.140 --> 00:03:02.933
Now, what would z squared be?

00:03:03.830 --> 00:03:05.700
Well, when you multiply complex numbers

00:03:05.700 --> 00:03:08.740
and you've represented them in polar form,

00:03:08.740 --> 00:03:11.570
we know that you would
multiply the moduli,

00:03:11.570 --> 00:03:13.690
so it would then be 2 squared.

00:03:13.690 --> 00:03:15.500
So it'd be 4 right over here.

00:03:15.500 --> 00:03:18.220
And then you would add the arguments.

00:03:18.220 --> 00:03:21.560
So you would essentially
rotate z by another 120 degrees

00:03:21.560 --> 00:03:23.000
'cause you're multiplying it by z.

00:03:23.000 --> 00:03:26.680
So it's going to be cosine of 240 degrees

00:03:26.680 --> 00:03:31.680
plus i sine of 240 degrees.

00:03:31.800 --> 00:03:34.440
Once again, 2 times 2 is equal to 4.

00:03:34.440 --> 00:03:38.290
120 degrees plus another
120 degrees is 240 degrees.

00:03:38.290 --> 00:03:41.240
And so now where would z squared sit?

00:03:41.240 --> 00:03:46.140
Well, its argument is 240
degrees and its modulus is 4.

00:03:46.140 --> 00:03:50.000
So now it is twice as far from the origin.

00:03:50.000 --> 00:03:51.930
And now let's think about what,

00:03:51.930 --> 00:03:53.520
I'll do this in a new color,

00:03:53.520 --> 00:03:56.563
what z to the third power
is going to be equal to.

00:03:57.420 --> 00:04:00.180
Well, that's going to be
z squared times z again.

00:04:00.180 --> 00:04:03.350
So we're gonna multiply
2 times this modulus.

00:04:03.350 --> 00:04:06.130
So that's going to be equal to 8 times,

00:04:06.130 --> 00:04:09.330
and then we're going to rotate
z squared by 120 degrees.

00:04:09.330 --> 00:04:14.330
So cosine of 360 degrees

00:04:14.870 --> 00:04:19.113
plus i sine of 360 degrees.

00:04:20.900 --> 00:04:25.270
And so that's going to put
us at 8 for our modulus.

00:04:25.270 --> 00:04:27.670
And 360 degrees is the
same thing as zero degrees.

00:04:27.670 --> 00:04:29.190
So we are right over here.

00:04:29.190 --> 00:04:32.260
So this is z to the third power.

00:04:32.260 --> 00:04:34.520
And I think, you know where this is going.

00:04:34.520 --> 00:04:37.480
What is z to the fourth power going to be?

00:04:37.480 --> 00:04:39.410
Let me move my screen down a little bit

00:04:39.410 --> 00:04:41.490
so I have a little more real estate.

00:04:41.490 --> 00:04:43.060
z to the 4th.

00:04:43.060 --> 00:04:45.260
Well, I'm just gonna
take this modulus here

00:04:45.260 --> 00:04:47.684
since I'm going to multiply
z to the third times z,

00:04:47.684 --> 00:04:51.810
I'm gonna multiply that
modulus times 2 to get to 16.

00:04:51.810 --> 00:04:55.370
And then I'm going to
add another 120 degrees.

00:04:55.370 --> 00:04:58.800
Well, I could write cosine of 480 degrees,

00:04:58.800 --> 00:05:01.760
or 360 degrees is the same
thing as zero degrees.

00:05:01.760 --> 00:05:05.710
So this I could say is zero
degrees. This is zero degrees.

00:05:05.710 --> 00:05:09.473
So if I add 120 to that, I
get cosine of 120 degrees.

00:05:11.504 --> 00:05:13.754
Plus i sine of 120 degrees.

00:05:15.910 --> 00:05:19.580
So my argument is back
to being at 120 degrees,

00:05:19.580 --> 00:05:21.790
but now my modulus is 16.

00:05:21.790 --> 00:05:23.740
So there's 4, 8, 12, 16,

00:05:23.740 --> 00:05:25.840
this outer circle right over here.

00:05:25.840 --> 00:05:29.910
I am right over there
with z to the fourth.

00:05:29.910 --> 00:05:30.910
So we're almost done.

00:05:30.910 --> 00:05:34.450
We've just represented z to
the fourth in polar form.

00:05:34.450 --> 00:05:37.780
Now we just have to think
about it in rectangular form.

00:05:37.780 --> 00:05:39.570
Now, lucky for us,

00:05:39.570 --> 00:05:42.020
we already know what
cosine of 120 degrees is

00:05:42.020 --> 00:05:45.430
and sine of 120 degrees is.

00:05:45.430 --> 00:05:48.160
It is, we can construct if we want

00:05:48.160 --> 00:05:52.410
another 30-60-90 triangle right over here.

00:05:52.410 --> 00:05:56.930
So the hypotenuse here has length 16.

00:05:56.930 --> 00:05:59.000
The short side is going to be 1/2 of that.

00:05:59.000 --> 00:06:00.320
So it has length 8.

00:06:00.320 --> 00:06:02.620
And then the long side is
gonna be square root of 3

00:06:02.620 --> 00:06:03.680
times the short side.

00:06:03.680 --> 00:06:06.170
So it's going to be 8 square roots of 3.

00:06:06.170 --> 00:06:08.180
So if we wanted to write z to the fourth

00:06:08.180 --> 00:06:10.690
in rectangular form,

00:06:10.690 --> 00:06:13.223
it would be the real part is -8.

00:06:14.270 --> 00:06:19.270
Plus i times 8 square
roots of 3, and we're done.


Indoor air pollutants

WEBVTT
Kind: captions
Language: en

00:00:00.530 --> 00:00:03.260
- [Instructor] Let's talk
about indoor air pollution.

00:00:03.260 --> 00:00:05.950
I remember when I first heard
about indoor air pollution

00:00:05.950 --> 00:00:08.320
in my AP environmental science class,

00:00:08.320 --> 00:00:10.370
I was a little confused.

00:00:10.370 --> 00:00:12.280
When I used to think of pollution,

00:00:12.280 --> 00:00:14.420
I would think of images like this

00:00:14.420 --> 00:00:15.850
or this.

00:00:15.850 --> 00:00:18.380
But pollution is often invisible,

00:00:18.380 --> 00:00:21.540
and it isn't just
restricted to the outdoors.

00:00:21.540 --> 00:00:25.170
Indoor air pollutants can lead
to serious health conditions

00:00:25.170 --> 00:00:26.930
and even death.

00:00:26.930 --> 00:00:29.030
But there are ways to identify

00:00:29.030 --> 00:00:31.400
and prevent indoor air pollution.

00:00:31.400 --> 00:00:33.360
Let's take a look at an example.

00:00:33.360 --> 00:00:34.730
This is Ava.

00:00:34.730 --> 00:00:37.560
And let's say Ava, like many
other people in the world,

00:00:37.560 --> 00:00:40.210
spends the majority of her time indoors.

00:00:40.210 --> 00:00:44.350
She works, sleeps, cooks,
and eats in her home.

00:00:44.350 --> 00:00:46.950
And lately, she's been
experiencing headaches

00:00:46.950 --> 00:00:48.630
and she's been coughing.

00:00:48.630 --> 00:00:51.620
A possible culprit is
indoor air pollution.

00:00:51.620 --> 00:00:54.730
So, where could the indoor
air pollution be coming from?

00:00:54.730 --> 00:00:57.010
Let's take a look at Ava's house.

00:00:57.010 --> 00:00:58.640
Indoor air pollution can come from

00:00:58.640 --> 00:01:00.610
many different kinds of sources,

00:01:00.610 --> 00:01:03.550
both human-made and natural.

00:01:03.550 --> 00:01:05.650
Ava's furniture, paneling, and carpets

00:01:05.650 --> 00:01:08.300
could be releasing
volatile organic compounds,

00:01:08.300 --> 00:01:11.130
which are often written down as VOCs,

00:01:11.130 --> 00:01:12.960
and they basically include substances

00:01:12.960 --> 00:01:17.080
that form gases at room
temperature, like formaldehyde.

00:01:17.080 --> 00:01:19.030
Formaldehyde is used as an adhesive

00:01:19.030 --> 00:01:21.110
in building materials and upholstery,

00:01:21.110 --> 00:01:22.990
and it can get into the air.

00:01:22.990 --> 00:01:25.560
This is the same stuff
that is used to embalm

00:01:25.560 --> 00:01:27.620
and preserve dead bodies.

00:01:27.620 --> 00:01:30.700
In other words, it's not
pleasant to breathe in.

00:01:30.700 --> 00:01:33.210
The United States
Environmental Protection Agency

00:01:33.210 --> 00:01:35.140
says that formaldehyde is one of the four

00:01:35.140 --> 00:01:38.320
most dangerous air
pollutants in the country.

00:01:38.320 --> 00:01:41.630
Formaldehyde can make
you dizzy and nauseated.

00:01:41.630 --> 00:01:45.610
And if you're exposed to
enough of it, it can kill you.

00:01:45.610 --> 00:01:48.880
Indoor air pollutants can also
come from Ava's house itself

00:01:48.880 --> 00:01:53.080
in the form of particulates,
which are teeny-tiny particles

00:01:53.080 --> 00:01:56.120
so small that they can
stay suspended in the air.

00:01:56.120 --> 00:01:58.320
And they can be really dangerous

00:01:58.320 --> 00:02:00.650
because they can travel
deep into the lungs

00:02:00.650 --> 00:02:02.480
and damage cells.

00:02:02.480 --> 00:02:05.460
One such particulate is asbestos.

00:02:05.460 --> 00:02:09.260
It's actually, in my opinion,
a really cool substance.

00:02:09.260 --> 00:02:11.060
It's an electrical insulator,

00:02:11.060 --> 00:02:14.210
and it's fireproof and it's acid-proof.

00:02:14.210 --> 00:02:16.880
And there was a time when
many houses were being built

00:02:16.880 --> 00:02:19.150
with asbestos in its building insulation,

00:02:19.150 --> 00:02:20.830
flooring, and roofing.

00:02:20.830 --> 00:02:24.060
It's actually a natural
material that's mined,

00:02:24.060 --> 00:02:27.630
and it has light fluffy fibers
that can be woven into cloth.

00:02:27.630 --> 00:02:30.460
To me, it always looked like unicorn hair.

00:02:30.460 --> 00:02:33.400
But really, it's more
like evil unicorn hair.

00:02:33.400 --> 00:02:36.080
Each fiber can break
into microscopic pieces

00:02:36.080 --> 00:02:37.580
that could scar your lungs

00:02:37.580 --> 00:02:41.050
and lead to lung cancer
and other lung diseases.

00:02:41.050 --> 00:02:42.640
Particulates in Ava's house

00:02:42.640 --> 00:02:44.650
could also be coming from the paint.

00:02:44.650 --> 00:02:47.920
Lead paint in Ava's house
could begin to chip away

00:02:47.920 --> 00:02:50.920
and could suspend small
particles in the air.

00:02:50.920 --> 00:02:53.320
These particles could
cause lead poisoning,

00:02:53.320 --> 00:02:56.730
which can cause headaches
and nerve and brain damage.

00:02:56.730 --> 00:02:59.430
The use of lead and
asbestos has been restricted

00:02:59.430 --> 00:03:01.400
by many governments around the world,

00:03:01.400 --> 00:03:04.363
but these materials can still
be found in older buildings.

00:03:05.480 --> 00:03:08.050
Another way inside air can become polluted

00:03:08.050 --> 00:03:11.393
is through combustion, which
is to say burning stuff.

00:03:12.240 --> 00:03:14.910
Combustion can cause a
wide variety of pollutants

00:03:14.910 --> 00:03:18.670
that can irritate lungs,
including carbon monoxide,

00:03:18.670 --> 00:03:22.823
nitrogen oxides, sulfur
dioxide, and particulates.

00:03:24.520 --> 00:03:27.900
One way that carbon monoxide
can build up inside a building

00:03:27.900 --> 00:03:30.370
is from a poorly-maintained furnace.

00:03:30.370 --> 00:03:33.440
Carbon monoxide molecules
have a secret weapon.

00:03:33.440 --> 00:03:35.760
They can trick the proteins in your blood

00:03:35.760 --> 00:03:37.740
into thinking they're oxygen.

00:03:37.740 --> 00:03:39.743
This can cause asphyxiation,

00:03:40.840 --> 00:03:43.520
which is when the body
cannot get enough oxygen,

00:03:43.520 --> 00:03:45.470
and it can be deadly.

00:03:45.470 --> 00:03:48.270
Ava should make sure that her
furnace is well maintained

00:03:48.270 --> 00:03:50.110
and serviced regularly.

00:03:50.110 --> 00:03:51.860
Combustion-related air pollution

00:03:51.860 --> 00:03:53.950
doesn't just come from furnaces, though.

00:03:53.950 --> 00:03:56.350
In less economically-developed countries,

00:03:56.350 --> 00:03:59.860
families sometimes use open
fires for heating and cooking.

00:03:59.860 --> 00:04:04.360
People often burn wood, peat,
and even coal inside homes

00:04:04.360 --> 00:04:06.690
without the necessary
ventilation to circulate

00:04:06.690 --> 00:04:08.970
and dilute the pollutants in the air.

00:04:08.970 --> 00:04:10.630
Combustion-related air pollution

00:04:10.630 --> 00:04:13.570
can also come from poorly
ventilated fireplaces

00:04:13.570 --> 00:04:14.923
and tobacco smoke.

00:04:16.150 --> 00:04:17.910
So, what could Eva do to reduce

00:04:17.910 --> 00:04:19.960
combustion-related air pollution?

00:04:19.960 --> 00:04:22.580
Well, she could open the windows

00:04:22.580 --> 00:04:24.760
and she could use fans to mix the smoke

00:04:24.760 --> 00:04:27.000
and pollution with outside air.

00:04:27.000 --> 00:04:30.030
Ava should also install a
carbon monoxide detector

00:04:30.030 --> 00:04:32.130
to make sure that the air is safe.

00:04:32.130 --> 00:04:34.750
A carbon monoxide detector
could also detect leaks

00:04:34.750 --> 00:04:36.993
from natural gas stoves or heaters.

00:04:37.930 --> 00:04:41.220
It's also possible that Ava's
house has natural pollutants,

00:04:41.220 --> 00:04:44.550
like mold, dust, or even radon.

00:04:44.550 --> 00:04:47.140
Mold is a type of microscopic fungus

00:04:47.140 --> 00:04:49.420
that's always floating around in the air,

00:04:49.420 --> 00:04:52.950
and breathing it in can cause
itchy eyes, runny noses,

00:04:52.950 --> 00:04:55.440
and it can trigger asthma attacks.

00:04:55.440 --> 00:04:58.200
And mold loves moisture.

00:04:58.200 --> 00:05:00.100
So, when the air is really humid,

00:05:00.100 --> 00:05:03.520
there will be more mold spores,
which is good for the molds,

00:05:03.520 --> 00:05:05.400
but bad for us.

00:05:05.400 --> 00:05:08.240
And what areas of the house
tend to have the most moisture?

00:05:08.240 --> 00:05:10.190
The bathrooms and the kitchen,

00:05:10.190 --> 00:05:12.980
so these areas especially
need to have windows

00:05:12.980 --> 00:05:15.960
that can be opened or air
fans that can draw moisture

00:05:15.960 --> 00:05:18.530
and the molds outta the house.

00:05:18.530 --> 00:05:22.300
Another kind of natural
indoor air pollutant is radon,

00:05:22.300 --> 00:05:25.360
which is a radioactive noble gas.

00:05:25.360 --> 00:05:27.110
It's produced by the natural decay

00:05:27.110 --> 00:05:29.443
of radioactive rocks in the ground.

00:05:30.550 --> 00:05:33.380
Let's say that Ava's
basement has some cracks

00:05:33.380 --> 00:05:35.530
in the foundation and the walls.

00:05:35.530 --> 00:05:37.550
That would mean that
when radon seeps upward

00:05:37.550 --> 00:05:40.210
through the soil, it
could enter these cracks

00:05:40.210 --> 00:05:42.920
and be stuck inside Ava's house.

00:05:42.920 --> 00:05:45.730
Breathing in too much radon
could damage lung tissue

00:05:45.730 --> 00:05:47.930
and even lead to lung cancer,

00:05:47.930 --> 00:05:50.000
depending on where the house is built.

00:05:50.000 --> 00:05:52.150
Some places, like Ava's house,

00:05:52.150 --> 00:05:54.940
are more likely to have radon than others.

00:05:54.940 --> 00:05:57.970
Ava can prevent radon exposure
by sealing up the cracks

00:05:57.970 --> 00:05:59.890
in the foundation of her house

00:05:59.890 --> 00:06:02.460
and by ventilating her basement.

00:06:02.460 --> 00:06:06.050
Some indoor air pollution
requires professional remediation.

00:06:06.050 --> 00:06:08.330
To get rid of asbestos, for example,

00:06:08.330 --> 00:06:11.030
an accredited asbestos
abatement specialist

00:06:11.030 --> 00:06:14.300
basically shows up in a
biohazard suit like this.

00:06:14.300 --> 00:06:16.500
That's how dangerous it is.

00:06:16.500 --> 00:06:18.000
For other situations,

00:06:18.000 --> 00:06:21.810
there's a simple solution to
Ava's problem: ventilation.

00:06:21.810 --> 00:06:23.050
Ava could open windows

00:06:23.050 --> 00:06:26.200
on the opposing sides of
her home just a crack.

00:06:26.200 --> 00:06:28.000
The outdoor air would flow in,

00:06:28.000 --> 00:06:30.090
dilute the indoor air pollutants,

00:06:30.090 --> 00:06:32.080
and carry them outta the house.

00:06:32.080 --> 00:06:35.260
This natural ventilation
allows the air to circulate

00:06:35.260 --> 00:06:38.400
and reduces the buildup
of indoor air pollutants.

00:06:38.400 --> 00:06:40.850
There are a lot of ways
that indoor air pollutants

00:06:40.850 --> 00:06:43.650
could sneak into Ava's house, from nature,

00:06:43.650 --> 00:06:47.050
from combustion, and
from human-made items.

00:06:47.050 --> 00:06:48.820
Being aware of these sources can help Ava

00:06:48.820 --> 00:06:50.490
make sure that the air inside her house

00:06:50.490 --> 00:06:52.653
is fresh, clean, and healthy.