Separation of Powers and Checks and Balances

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- [Instructor] This is a great excerpt

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from Federalist 51 by James Madison.

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And just as a reminder,
the the Federalist Papers,

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which were written by
Hamilton, Madison, John Jay,

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were an attempt to get
the Constitution passed,

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to get it ratified.

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So these were really kind of op-eds

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that they were publishing
to convince people.

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But this is a great passage.

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If men were angels, no
government would be necessary.

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If angels were to govern men,

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neither external nor internal
controls on government

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would be necessary.

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In framing a government

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which is to be administered
by men over men,

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the great difficulty lies in this:

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you must first enable the government

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to control the governed;

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and in the next place
oblige it to control itself.

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And it goes on to talk about
how we can keep government

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from becoming too powerful

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by so contriving the interior
structure of the government

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as that its several constituent parts may,

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by their mutual relations,

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be the means of keeping each
other in their proper places.

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And so remember, this was in
defense of the Constitution,

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so arguably this was in place,

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that somehow this
Constitution had contrived

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an interior structure

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so that the several constituent
parts of government,

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by their mutual relations,

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would keep each other
in their proper places,

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or you could even say
keep each other in check.

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So in line with this passage,

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there's really two big ideas
embedded in the Constitution

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as to how our government is structured.

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The first is this notion
of separation of powers.

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We have three branches of government.

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You have your executive,
headed by the president.

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You have your legislative
branch, which is Congress.

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Legislative.

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And you have your judicial branch,

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which is the US Supreme Court.

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And this notion of separation of powers

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is that you have these

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fairly independent branches of government,

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and the idea was to make
them reasonably independent

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so that one group, one branch,

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could not take over the others.

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The legislative branch, Congress,

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they're charged with budget,

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and they're charged with
creating and passing laws.

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The executive branch,
headed by the president,

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is supposed to execute,
run the government,

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based on the laws that Congress passes.

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And you have the judicial branch

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that would decide whether things,

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say laws that Congress is passing,

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or actions that the executive's taking,

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they say, "Hey, is that constitutional?"

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Or they can interpret laws.

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So these different powers

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are put into these different branches.

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The powers are separate.

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Now related to that is
another very powerful idea,

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and this is keeping each
other in their proper places,

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and so this is the idea
of checks and balances.

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Each of these can't do whatever they want.

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They're all balancing each other.

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They all have checks on each other.

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For example, the executive can
veto the legislative branch,

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can veto a law passed by Congress,

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but then the legislative
branch can override that veto.

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The legislative branch,
they control the budget,

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so it's not like the
president or the executive

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can do whatever they want,

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or that they can just spend
as much money as they want,

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and the judicial branch, in
both cases, can be a check,

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and they're saying, "Hey,
you're doing something

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"that is unconstitutional," or,

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"We're going to interpret the laws

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"that the legislature has passed."

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The executive appoints the judicial,

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but even there, you have to
get congressional buy-in.

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So once again,

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you have these independent
branches of government,

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all the power isn't in one,
and they are interdependent.

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They provide checks and
balances on each other,

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and this is all about what
Federalist 51 is talking about,

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so that by their mutual relations,

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they are the means of keeping each other

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in their proper places.


The impact of constitutional compromises on us today

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- [Instructor] When you first learn about

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the Constitutional Convention in 1787

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and the debates and the compromises,

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it's easy to assume that, okay,

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that's interesting from a
historical point of view,

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but how does it affect me today?

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Well the simple answer is,
it affects you incredibly,

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those compromises that were
made over 200 years ago.

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So the most obvious question is,

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well what were those compromises?

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Well, to even start to
appreciate the compromises,

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let's start with this
picture, or this chart,

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of the census in 1790, so it
gives a pretty good snapshot

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of what the United States looked like

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after the Constitution was ratified.

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So, as you can see, the
population as a whole

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was much smaller than it is today,

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it was roughly, a little
under four million people,

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today the United States is
over 300 million people,

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and then you also see a pretty big

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population difference between the states.

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You have big states, like Virginia,

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which, at the time, had 750,000 people,

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and then you had small
states like Delaware,

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that had 60,000 people,
or you have Rhode Island,

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that has a little under 70,000 people.

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And so you can imagine, the Virginians,

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or the people from
Massachusetts might have said,

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hey we want representation
in the legislative,

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in Congress, to be based on population.

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It should be, you know,
we have a lot of people,

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we should get more of a say,

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while someone from, say, Delaware,

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might say, wait, hold on a second,

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under the Articles of Confederation

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we were a sovereign state, we don't wanna

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just become, you know, do
whatever the Virginians

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or the people from Massachusetts wanna do,

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we wanna have a more equal say,

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and of course, the big
state folks would have said,

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whoa, no, then your population,
people in your population,

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in your state, are going
to be overrepresented.

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And so this was a serious debate,

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and it resulted in what is
called the Great Compromise.

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The Great Compromise, which is probably

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the most cited compromise coming
out of the US Constitution.

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And it's the notion of, okay,
well let's have it both ways.

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In the legislative,
let's create two houses,

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let's do one house that
is based on population,

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so the House of Representatives,

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where Virginia will get more
representation than a Delaware,

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but let's make another
house called the Senate,

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where every state has
equal representation,

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where you have two senators per state.

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And to appreciate that this is,

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even today, a controversial thing,

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here is an article from the
New York Times, from 2013.

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This is an article that's
talking about perceived

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inequalities of per
person federal funding,

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and it says, and the
article is literally named,

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'Big State, Small State,'
"Vermont's 625,000 residents

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"have two United States senators,

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"and so do New York's 19 million.

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"that means that a Vermonter
has 30 times the voting power

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"in the Senate of a New Yorker
just over the state line,

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"the biggest inequality
between two adjacent states.

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"The nation's largest gap,
between Wyoming and California,

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"is more than double that."

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So they're making the argument
that, at least in the Senate,

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a person in Vermont has 30
times the representation

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as a person in New York,

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and if you compare Wyoming and California,

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it's a factor of 60.

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And they say, "The difference
reflects the growing disparity

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"in their citizens' voting
power, and it is not an anomaly.

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"The Constitution has
always given residents

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"of states with small populations a lift."

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So this is coming straight
out of the Great Compromise,

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"but the size and importance of the gap

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"has grown markedly in recent decades,

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"in ways the framers
probably never anticipated."

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So you can imagine, this
is the New York Times,

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so they probably might favor a little bit

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more representation for New Yorkers,

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but it's an interesting
thing to think about.

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The Constitution was
written over 200 years ago.

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Could they have predicted
how much the United States

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would grow, or get a
movement to the cities,

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even in that census of 1790,

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we saw a factor of a little more than 10

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between a Virginia and,
say, a Rhode Island,

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but now we're talking about a factor of 60

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between California and Wyoming.

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There's no right answer, here,

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but it is something very
interesting to think about

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and as you can see, it's
something that people

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are even talking about today.

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Now, the other significant compromise

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that is also talked a
lot about, these days,

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is the notion of the electoral college.

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So, people who are more in
the anti-Federalist camp,

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they were more in favor of
a participatory democracy,

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a direct democracy, where
you have one person one vote,

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and whoever gets the majority
of the vote in the country,

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well, maybe they should be president.

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But Federalists, especially
folks like James Madison,

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they were a little suspicious
of just the crowd voting

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whoever they wanted.

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They wanted it to go through a filter

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with the idea that maybe that filter

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could temper the passions
of the crowd, so to speak,

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and so they devised this system

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where it isn't one person one vote,

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but every state has a
certain number of electors.

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So you vote for electors,
and then the states send them

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and then they can place
their vote for President.

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It turns out that most states have decided

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to have a winner take all policy,

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so that maybe they could matter more

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for the Presidential election.

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But what that's resulted in,
is if you take a big state,

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like Texas, and just draw
a quick drawing of Texas,

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or a big state like
California, right over here,

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in a winner take all, as
soon as you cross 50%,

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you get 50.1% in either
one of these states,

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and in other big states,
it's true in most states,

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well then you'll get all of
the electors for that state.

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So even if you get 70%
of the vote in Texas,

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or 70% of the vote of California,

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it's equivalent to getting 50.1%.

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The reason why this has resulted
in some significant debate,

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in the recent past, you
had two major elections

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where the electoral college majority

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was different than the popular majority.

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You had Bush vs. Gore in 2000

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and you have Trump vs. Clinton in 2016.

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Now, two of the other major compromises

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that came out of the
Constitutional Convention

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are less debated today,
and that's a good thing,

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because they were resolved, finally,

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in 1865 by the 13th amendment,

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that came out of the Civil War.

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And these were around slavery.

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You have the 3/5 Compromise,

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and this is, actually, still

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more of a notion around representation.

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Even in the House, how do you determine

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the population that's gonna dictate

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how many representatives you get?

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What about slaves?

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If you look back to this
chart right over here,

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notice some of the southern states

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had a significant fraction
of their population

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that were slaves.

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And so you can imagine
that their delegates

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were saying, hey, we wanna
count them in the population.

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They didn't want them to vote,

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but they said, hey, when we decide

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how many representatives we get,

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we wanna count these
293,000 people in Virginia

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when we decide how many
representatives they get.

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And you can imagine, other states,

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either just because they didn't wanna

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dilute their own representation,

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or maybe even some of them might have felt

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morally against something like slavery,

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said, wait, no, you
shouldn't get a benefit

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because you're doing this
thing called slavery,

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and so they were against it.

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And so the compromise, and
once again, James Madison

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was significantly involved here,

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was the 3/5 Compromise, that
for determining representation,

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a slave would count as 3/5 of a person,

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which is offensive to our sensibilities,

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but that's the compromise
they came up with,

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but it didn't become, it
wasn't an issue anymore

00:07:12.935 --> 00:07:16.193
once slavery was abolished
by the 13th amendment.

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The last major compromise
that people will talk about,

00:07:18.567 --> 00:07:20.681
and this one also revolves around slavery,

00:07:20.681 --> 00:07:24.181
is the importation, importation of slaves.

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During the Revolution,
because Great Britain

00:07:28.530 --> 00:07:31.307
had such a significant
role in the slave trade,

00:07:31.307 --> 00:07:34.813
the colonies, or the
states, the nascent states,

00:07:34.813 --> 00:07:37.029
were pretty unified
around not participating,

00:07:37.029 --> 00:07:39.192
at least with Great Britain,

00:07:39.192 --> 00:07:41.230
but once the Revolution was over,

00:07:41.230 --> 00:07:42.597
this became an issue again.

00:07:42.597 --> 00:07:44.866
Some states did not want
more importation of slaves,

00:07:44.866 --> 00:07:47.424
some did, and so the
compromise that was reached is

00:07:47.424 --> 00:07:49.157
that at least for 20 years,

00:07:49.157 --> 00:07:51.310
the Congress would not pass a law

00:07:51.310 --> 00:07:54.333
that is prohibiting the
importation of slaves.

00:07:54.333 --> 00:07:56.976
And it turns out, almost
exactly 20 years later,

00:07:56.976 --> 00:07:59.235
once that expired from the Constitution,

00:07:59.235 --> 00:08:01.280
under Thomas Jefferson, they did

00:08:01.280 --> 00:08:03.721
ban the importation of slaves officially,

00:08:03.721 --> 00:08:05.980
although it still
continued to some degree,

00:08:05.980 --> 00:08:07.068
at a much smaller level.

00:08:07.068 --> 00:08:10.351
I'll leave you there, but
the big appreciation here

00:08:10.351 --> 00:08:13.497
is that those debates that we talk about,

00:08:13.497 --> 00:08:15.738
the Great Compromise,
the electoral college,

00:08:15.738 --> 00:08:17.674
these debates around representation,

00:08:17.674 --> 00:08:20.016
that we saw over 200 years ago,

00:08:20.016 --> 00:08:23.128
these are things that people
still feel passionate about,

00:08:23.128 --> 00:08:25.461
and they still debate today.


Introduction to cilia, flagella and pseudopodia

WEBVTT
Kind: captions
Language: en

00:00:00.659 --> 00:00:02.610
- [Instructor] The goal of
this video is to appreciate

00:00:02.610 --> 00:00:04.328
some of the structures that you see

00:00:04.328 --> 00:00:07.161
even in unicellular organisms.

00:00:07.161 --> 00:00:09.413
So this right over here
is a picture of the amoeba

00:00:09.413 --> 00:00:10.913
Chaos carolinense.

00:00:12.153 --> 00:00:14.754
And what you see here is
a projection coming off

00:00:14.754 --> 00:00:16.867
from the main part of the cell,

00:00:16.867 --> 00:00:19.119
and this is called a pseudopod,

00:00:19.119 --> 00:00:21.975
which is referring to
it being a false foot.

00:00:21.975 --> 00:00:24.947
The pod is coming from the
same root word as podiatry,

00:00:24.947 --> 00:00:26.874
which is referring to the foot.

00:00:26.874 --> 00:00:28.198
And what I really want you to appreciate,

00:00:28.198 --> 00:00:31.193
this is used by amoeba
either to move around

00:00:31.193 --> 00:00:33.469
or it could be even
used to attack something

00:00:33.469 --> 00:00:35.257
that it wants to engulf.

00:00:35.257 --> 00:00:38.275
And think about what it might
take to be able to do this,

00:00:38.275 --> 00:00:40.899
to be able to grow this
type of a pseudo foot,

00:00:40.899 --> 00:00:42.664
this type of a false foot.

00:00:42.664 --> 00:00:45.961
You need all sorts of
microstructures in here

00:00:45.961 --> 00:00:48.492
that will extend or contract as necessary.

00:00:48.492 --> 00:00:50.605
And think about the machinery
that you need to do that.

00:00:50.605 --> 00:00:52.277
And so the key realization is,

00:00:52.277 --> 00:00:54.901
sometimes we just imagine cells as these

00:00:54.901 --> 00:00:57.525
bags of fluid with a few
things floating around.

00:00:57.525 --> 00:00:59.940
But they're these incredibly
complex structures,

00:00:59.940 --> 00:01:02.401
and biologists even today
don't fully understand

00:01:02.401 --> 00:01:04.235
how everything works and they're studying

00:01:04.235 --> 00:01:07.417
how these things actually come to be.

00:01:07.417 --> 00:01:09.460
Now another structure
that you'll often see

00:01:09.460 --> 00:01:13.477
in unicellular organisms that
either help them move around

00:01:13.477 --> 00:01:18.307
or even help move other
things around are cilia.

00:01:18.307 --> 00:01:22.602
So this right over here is a
picture of Oxytricha trifallax,

00:01:22.602 --> 00:01:24.390
which is a unicellular organism.

00:01:24.390 --> 00:01:25.714
It's a eukaryote.

00:01:25.714 --> 00:01:27.200
And you can clearly see these projections

00:01:27.200 --> 00:01:28.640
from its body here,

00:01:28.640 --> 00:01:30.079
these hairlike structures.

00:01:30.079 --> 00:01:32.703
Remember this is a unicellular organism.

00:01:32.703 --> 00:01:34.561
If we were to, it's actually a fairly,

00:01:34.561 --> 00:01:36.163
it's a decent sized one.

00:01:36.163 --> 00:01:39.112
That would be about, something
like that would be about

00:01:39.112 --> 00:01:41.828
30 micrometers right over there

00:01:41.828 --> 00:01:44.754
or 30 millionths of a
meter or 30 thousandths

00:01:44.754 --> 00:01:46.124
of a millimeter.

00:01:46.124 --> 00:01:47.959
So small by our scale, but
it's actually pretty big

00:01:47.959 --> 00:01:50.699
on the scale of it being a cell.

00:01:50.699 --> 00:01:53.856
And once again, these cilia
tend to move in unison

00:01:53.856 --> 00:01:56.852
to either allow the
microorganism to move around

00:01:56.852 --> 00:01:59.986
or sometimes they're used
to move other things around.

00:01:59.986 --> 00:02:02.123
For examples the cells
that line your lungs

00:02:02.123 --> 00:02:05.002
will have cilia that
are used to move things

00:02:05.002 --> 00:02:08.137
up or down, to move some of
the saliva or any particles

00:02:08.137 --> 00:02:10.157
that are in there.

00:02:10.157 --> 00:02:13.477
Now Oxytricha trifallax is
particularly interesting

00:02:13.477 --> 00:02:17.192
as a eukaryote because it
doesn't just have one nucleus.

00:02:17.192 --> 00:02:19.468
It can have two nuclei.

00:02:19.468 --> 00:02:21.001
And within the nucleus,

00:02:21.001 --> 00:02:23.648
it's DNA can be extremely fragmented.

00:02:23.648 --> 00:02:25.784
Most organisms have

00:02:25.784 --> 00:02:28.361
a reasonable number of chromosomes.

00:02:28.361 --> 00:02:30.381
Human beings have 23 pair.

00:02:30.381 --> 00:02:32.634
That's actually a fairly large number.

00:02:32.634 --> 00:02:37.208
Oxytricha trifallax could
have thousands of chromosomes.

00:02:37.208 --> 00:02:39.994
And what's really interesting
about Oxytricha trifallax

00:02:39.994 --> 00:02:41.643
is how it mates.

00:02:41.643 --> 00:02:43.268
When it is under stress,

00:02:43.268 --> 00:02:46.589
it will merge with another
Oxytricha trifallax,

00:02:46.589 --> 00:02:48.911
and instead of producing
another offspring,

00:02:48.911 --> 00:02:51.349
they mingle their DNA together.

00:02:51.349 --> 00:02:54.902
So by mating, they change
each other's genetic makeup,

00:02:54.902 --> 00:02:56.643
which is fascinating.

00:02:56.643 --> 00:02:59.104
And depending on your
perspective, highly romantic.

00:02:59.104 --> 00:03:01.310
Now another related idea
is instead of having

00:03:01.310 --> 00:03:04.840
many cilia, some unicellular
organisms will just have

00:03:04.840 --> 00:03:08.067
one large thing that looks like a tail

00:03:08.067 --> 00:03:11.504
that they can whip around to move.

00:03:11.504 --> 00:03:15.405
So this right over here is a
commonly studied green algae.

00:03:15.405 --> 00:03:17.634
It's called Chlamydomonas,

00:03:17.634 --> 00:03:20.537
and you can see very
clearly here this flagellum,

00:03:20.537 --> 00:03:22.766
this tail-like structure.

00:03:22.766 --> 00:03:24.852
And this is extremely thin.

00:03:24.852 --> 00:03:27.732
We're seeing it under a
very powerful microscope

00:03:27.732 --> 00:03:28.893
right over here,

00:03:28.893 --> 00:03:31.540
but just to get a sense of scale.

00:03:31.540 --> 00:03:35.394
A micrometer here would be about that.

00:03:35.394 --> 00:03:37.507
So the width of this flagellum,

00:03:37.507 --> 00:03:38.761
flagellum would be the singular.

00:03:38.761 --> 00:03:40.061
If we were talking about many of these,

00:03:40.061 --> 00:03:41.803
we would say flagella.

00:03:41.803 --> 00:03:45.193
This is about 1/4 of a micrometer.

00:03:45.193 --> 00:03:46.238
Another way of thinking about it,

00:03:46.238 --> 00:03:48.978
you could put 4,000 of these side by side,

00:03:48.978 --> 00:03:51.021
and you would have the
width of a millimeter.

00:03:51.021 --> 00:03:52.647
So extremely extremely small,

00:03:52.647 --> 00:03:54.899
but once again, it really is amazing

00:03:54.899 --> 00:03:57.685
that these what seem like
simple organisms to us

00:03:57.685 --> 00:03:59.148
are actually quite complex.

00:03:59.148 --> 00:04:02.910
There's a whole study of how
these flagella move around,

00:04:02.910 --> 00:04:06.811
how the cell can spin it
around so it allows it to move.

00:04:06.811 --> 00:04:09.063
If you were to actually
decompose what's going on

00:04:09.063 --> 00:04:10.596
in this part of the cell,

00:04:10.596 --> 00:04:12.128
it's actually quite complex.

00:04:12.128 --> 00:04:14.055
It's biological machinery going on.

00:04:14.055 --> 00:04:17.144
So once again, these
cells are not these just

00:04:17.144 --> 00:04:19.350
bags of just a few things floating around.

00:04:19.350 --> 00:04:21.068
They're incredibly complex structures

00:04:21.068 --> 00:04:24.318
that we are still trying to understand.


Organelles in eukaryotic cells

WEBVTT
Kind: captions
Language: en

00:00:00.271 --> 00:00:01.563
- [Instructor] What we're
going to do in this video

00:00:01.563 --> 00:00:03.504
is give ourselves a little bit of a tour

00:00:03.504 --> 00:00:05.171
of eukaryotic cells.

00:00:06.393 --> 00:00:07.647
And the first place to start

00:00:07.647 --> 00:00:08.945
is just to remind ourselves

00:00:08.945 --> 00:00:11.956
what it means for a cell to be eukaryotic.

00:00:11.956 --> 00:00:15.276
It means that inside the cell,

00:00:15.276 --> 00:00:18.341
there are membrane-bound organelles.

00:00:18.341 --> 00:00:19.833
Now, what does that mean?

00:00:19.833 --> 00:00:23.984
Well, you could view it as
sub-compartments within the cell.

00:00:23.984 --> 00:00:26.151
Membrane-bound organelles.

00:00:27.838 --> 00:00:29.401
And in this video in particular,

00:00:29.401 --> 00:00:30.578
we're going to highlight

00:00:30.578 --> 00:00:32.839
some of these membrane-bound organelles

00:00:32.839 --> 00:00:35.280
that make the cells eukaryotic.

00:00:35.280 --> 00:00:37.091
So let's just start with
some of the ingredients

00:00:37.091 --> 00:00:39.319
that we know is true of all cells.

00:00:39.319 --> 00:00:42.871
So you'll have your
cellular membrane here.

00:00:42.871 --> 00:00:44.820
I drew it big, so that
we have a lot of space

00:00:44.820 --> 00:00:46.320
to draw things in.

00:00:47.388 --> 00:00:50.257
So this is our cellular membrane.

00:00:50.257 --> 00:00:52.135
I'll do some nice shading

00:00:52.135 --> 00:00:54.413
so you appreciate that it'll
actually be three-dimensional.

00:00:54.413 --> 00:00:56.143
We see so many slices of cells

00:00:56.143 --> 00:00:59.475
that sometimes we forget
that they are more spherical,

00:00:59.475 --> 00:01:02.329
or that they have
three-dimensional shape to them.

00:01:02.329 --> 00:01:03.329
They're not all spherical.

00:01:03.329 --> 00:01:04.793
They can have different shapes.

00:01:04.793 --> 00:01:07.126
Now all cells, and there
are some exceptions

00:01:07.126 --> 00:01:08.936
that we've talked about
in previous videos.

00:01:08.936 --> 00:01:10.209
I should say, most cells

00:01:10.209 --> 00:01:12.671
will have some genetic information in them

00:01:12.671 --> 00:01:14.254
in the form of DNA.

00:01:16.097 --> 00:01:19.524
So that is our DNA, right over there.

00:01:19.524 --> 00:01:22.962
Now, one of the key characteristics
of a eukaryotic cell

00:01:22.962 --> 00:01:24.965
is that the genetic information

00:01:24.965 --> 00:01:28.880
is going to be inside a
membrane-bound organelle.

00:01:28.880 --> 00:01:30.462
And that membrane-bound organelle,

00:01:30.462 --> 00:01:34.398
or the membrane that
surrounds the DNA here,

00:01:34.398 --> 00:01:36.815
that is the nuclear membrane.

00:01:37.702 --> 00:01:41.167
So let me draw the nuclear
membrane right over here,

00:01:41.167 --> 00:01:43.534
and I'll put some shading
in to appreciate that that

00:01:43.534 --> 00:01:48.232
also is going to be in three
dimensions, around the DNA.

00:01:48.232 --> 00:01:52.370
So that is the first
membrane-bound organelle

00:01:52.370 --> 00:01:56.000
that we're gonna discuss, the nucleus.

00:01:56.000 --> 00:01:57.938
Now the nucleus, it turns out,

00:01:57.938 --> 00:02:01.506
is connected to another
membrane-bound organelle.

00:02:01.506 --> 00:02:04.026
And we're gonna study
this in future videos,

00:02:04.026 --> 00:02:06.151
but right here I'm drawing holes or pores

00:02:06.151 --> 00:02:07.742
in the nuclear membrane.

00:02:07.742 --> 00:02:10.280
And those pores connect to something,

00:02:10.280 --> 00:02:14.509
it's a very fancy word called
the endoplasmic reticulum.

00:02:14.509 --> 00:02:16.214
And the endoplasmic reticulum

00:02:16.214 --> 00:02:19.886
is essentially these
layers of these membranes.

00:02:19.886 --> 00:02:21.488
So I'm gonna do my best job

00:02:21.488 --> 00:02:24.492
at trying to draw an
endoplasmic reticulum.

00:02:24.492 --> 00:02:27.583
Imagine extending from these pores,

00:02:27.583 --> 00:02:32.018
going into a space that has
really these layered membranes

00:02:32.018 --> 00:02:33.899
that have a lot of surface area.

00:02:33.899 --> 00:02:35.860
And I'm not gonna go all
the way around this nucleus,

00:02:35.860 --> 00:02:37.742
but in many cells it will go around,

00:02:37.742 --> 00:02:40.106
all the way around the nucleus.

00:02:40.106 --> 00:02:44.772
And this right over here, and
this is just a rough diagram.

00:02:44.772 --> 00:02:48.022
That is our endoplasmic, endoplasmic...

00:02:49.722 --> 00:02:51.972
Not blasmic, endoplasmic...

00:02:53.625 --> 00:02:55.458
Endoplasmic reticulum,

00:02:56.423 --> 00:02:58.466
which I've mentioned in previous videos

00:02:58.466 --> 00:03:00.844
would be an excellent name for a band.

00:03:00.844 --> 00:03:03.238
And what goes on in the
endoplasmic reticulum

00:03:03.238 --> 00:03:05.687
is when you are in the process

00:03:05.687 --> 00:03:09.263
of taking that genetic
information from DNA,

00:03:09.263 --> 00:03:10.539
and as we talk about in other videos

00:03:10.539 --> 00:03:13.039
it gets transcribed into mRNA.

00:03:15.983 --> 00:03:18.574
So that mRNA is now
containing that information.

00:03:18.574 --> 00:03:22.278
That mRNA will make its way
out of that nuclear membrane

00:03:22.278 --> 00:03:23.857
through one of these pores,

00:03:23.857 --> 00:03:25.816
and then make its way to a ribosome

00:03:25.816 --> 00:03:27.642
that is attached to the membrane

00:03:27.642 --> 00:03:29.975
of the endoplasmic reticulum.

00:03:29.975 --> 00:03:32.193
And so that's a ribosome there.

00:03:32.193 --> 00:03:34.849
I'm gonna do a bunch of ribosomes.

00:03:34.849 --> 00:03:37.185
And so as we've talked
about in previous videos,

00:03:37.185 --> 00:03:39.530
ribosomes are really where you take

00:03:39.530 --> 00:03:42.061
that genetic information from that mRNA,

00:03:42.061 --> 00:03:45.252
and then you translate it into a protein.

00:03:45.252 --> 00:03:47.785
So the ribosomes are
the protein synthesis,

00:03:47.785 --> 00:03:49.376
so let me label that.

00:03:49.376 --> 00:03:52.543
So this right over here is a ribosome.

00:03:54.111 --> 00:03:55.340
And some ribosomes

00:03:55.340 --> 00:03:57.851
might be attached to the
endoplasmic reticulum.

00:03:57.851 --> 00:03:59.406
Some of them might just be floating

00:03:59.406 --> 00:04:01.016
out here in the cytoplasm,

00:04:01.016 --> 00:04:04.225
so that would be a free ribosome.

00:04:04.225 --> 00:04:05.392
Free ribosome.

00:04:06.593 --> 00:04:07.986
And even from the point of view

00:04:07.986 --> 00:04:09.653
of the endoplasmic reticulum,

00:04:09.653 --> 00:04:11.489
the parts of the endoplasmic reticulum

00:04:11.489 --> 00:04:14.012
where you have ribosomes attached,

00:04:14.012 --> 00:04:18.517
this is known as rough
endoplasmic reticulum.

00:04:18.517 --> 00:04:20.972
It's the ribosomes that
are making them rough.

00:04:20.972 --> 00:04:22.673
It looks that way in a microscope.

00:04:22.673 --> 00:04:24.550
So I'll just say rough ER,

00:04:24.550 --> 00:04:26.712
for endoplasmic reticulum for short.

00:04:26.712 --> 00:04:28.803
And then you also have parts
of the endoplasmic reticulum

00:04:28.803 --> 00:04:31.621
where you do not have ribosomes attached.

00:04:31.621 --> 00:04:34.318
And because that looks smooth
through our microscope,

00:04:34.318 --> 00:04:36.559
it has been called, you can imagine,

00:04:36.559 --> 00:04:38.976
smooth endoplasmic reticulum.

00:04:43.763 --> 00:04:46.427
There are things known as golgi bodies.

00:04:46.427 --> 00:04:48.645
Once again, another fascinating name.

00:04:48.645 --> 00:04:50.440
You gotta love these names in biology.

00:04:50.440 --> 00:04:53.054
That look kind of like
an endoplasmic reticulum,

00:04:53.054 --> 00:04:56.679
but detached from the nuclear membrane.

00:04:56.679 --> 00:04:58.896
So let's say it's something like that.

00:04:58.896 --> 00:05:01.056
That's my best drawing there.

00:05:01.056 --> 00:05:02.723
That's a golgi body.

00:05:03.586 --> 00:05:07.464
And these are really good
at packaging molecules,

00:05:07.464 --> 00:05:09.635
even proteins that might've
just been produced,

00:05:09.635 --> 00:05:11.981
and packaging them so
that they can be used

00:05:11.981 --> 00:05:14.485
outside of the cell, for example.

00:05:14.485 --> 00:05:16.741
And we'll go into detail in other videos,

00:05:16.741 --> 00:05:18.633
where a protein might
go to the golgi body,

00:05:18.633 --> 00:05:20.358
get a little envelope around it,

00:05:20.358 --> 00:05:22.332
get some little processing going on,

00:05:22.332 --> 00:05:25.553
and then make its way outside of a cell.

00:05:25.553 --> 00:05:26.655
Now another,

00:05:26.655 --> 00:05:28.337
and this is maybe one of the most famous

00:05:28.337 --> 00:05:31.307
membrane-bound organelles
outside of the nucleus,

00:05:31.307 --> 00:05:33.992
is what's known as the
powerhouse of the cell,

00:05:33.992 --> 00:05:36.071
and that is the mitochondria.

00:05:36.071 --> 00:05:38.695
So I'll draw this mitochondria in magenta,

00:05:38.695 --> 00:05:41.261
because that's a nice powerful color.

00:05:41.261 --> 00:05:42.720
So mitochondria.

00:05:42.720 --> 00:05:44.032
And I love mitochondria

00:05:44.032 --> 00:05:46.101
because it's fascinating
how they even came to be.

00:05:46.101 --> 00:05:48.978
Mitochondria actually have their own DNA,

00:05:48.978 --> 00:05:51.660
and all of your mitochondrial
DNA comes from your mother.

00:05:51.660 --> 00:05:52.999
So that's actually very interesting

00:05:52.999 --> 00:05:55.715
for tracing maternal lineage.

00:05:55.715 --> 00:05:58.246
But mitochondria, this is where your,

00:05:58.246 --> 00:06:00.102
I'm gonna say let's see what
we could see inside of this.

00:06:00.102 --> 00:06:02.171
This is where you ATP is produced.

00:06:02.171 --> 00:06:04.547
This is your mitochondria.

00:06:04.547 --> 00:06:06.745
It's really the powerhouse of the cell.

00:06:06.745 --> 00:06:08.057
What's interesting about mitochondria

00:06:08.057 --> 00:06:09.775
is evolutionary biologists believe

00:06:09.775 --> 00:06:12.190
that the ancestors of mitochondria,

00:06:12.190 --> 00:06:14.199
because mitochondria have their own DNA,

00:06:14.199 --> 00:06:18.100
they might've been independent
organisms, independent cells.

00:06:18.100 --> 00:06:20.468
And at some point in
our evolutionary past,

00:06:20.468 --> 00:06:22.627
they started living in symbiosis

00:06:22.627 --> 00:06:26.794
inside of what would be
the ancestors of our cells.

00:06:27.713 --> 00:06:30.058
And over time, they became so codependent

00:06:30.058 --> 00:06:32.563
that they started to replicate together.

00:06:32.563 --> 00:06:33.970
And mitochondria, in fact,

00:06:33.970 --> 00:06:37.523
became part of these eukaryotic cells.

00:06:37.523 --> 00:06:40.687
Now if this eukaryotic
cell was a plant cell

00:06:40.687 --> 00:06:43.328
or maybe an algae cell,

00:06:43.328 --> 00:06:46.323
you would have something
called chloroplasts there.

00:06:46.323 --> 00:06:48.599
We don't have them because
we don't have photosynthesis,

00:06:48.599 --> 00:06:50.351
but this is a chloroplast.

00:06:50.351 --> 00:06:51.455
And if you could see inside,

00:06:51.455 --> 00:06:55.018
you could see the little
thylakoid stacks right over here.

00:06:55.018 --> 00:06:57.872
You could see the thylakoids
if you could see inside.

00:06:57.872 --> 00:07:00.889
And so this right over
here is a chloroplast.

00:07:00.889 --> 00:07:01.889
Chloroplast.

00:07:03.501 --> 00:07:06.418
And this would be plants and algae.

00:07:07.639 --> 00:07:09.389
Animals do not have these.

00:07:09.389 --> 00:07:12.550
And these are where you have
your photosynthesis take place.

00:07:12.550 --> 00:07:13.800
Photosynthesis.

00:07:15.266 --> 00:07:17.724
Now there's also some
membrane-bound organelles

00:07:17.724 --> 00:07:20.524
that are maybe less famous
than the mitochondria

00:07:20.524 --> 00:07:23.691
or the chloroplast, or
for sure the nucleus,

00:07:23.691 --> 00:07:26.490
and that might be
something like a vacuole.

00:07:26.490 --> 00:07:29.090
And in plants, vacuoles
tend to be very big.

00:07:29.090 --> 00:07:31.486
I could draw it, this is three-dimensional

00:07:31.486 --> 00:07:34.142
so I'll draw it on top of
something that I've drawn before.

00:07:34.142 --> 00:07:37.721
So if a vacuole right
over here, this is a...

00:07:37.721 --> 00:07:38.777
And in a plant

00:07:38.777 --> 00:07:40.461
it could be a fairly
significant compartment inside.

00:07:40.461 --> 00:07:42.689
And in fact, it can even give
structure to the plant itself

00:07:42.689 --> 00:07:45.009
because it is so big.

00:07:45.009 --> 00:07:48.065
And it contains water and enzymes.

00:07:48.065 --> 00:07:51.127
It's viewed as kind of
a storage compartment.

00:07:51.127 --> 00:07:55.178
But it can also contain enzymes
that help digest things,

00:07:55.178 --> 00:07:57.025
that help break things down

00:07:57.025 --> 00:07:59.709
so that they can be used in some way.

00:07:59.709 --> 00:08:02.274
So that is a vacuole.

00:08:02.274 --> 00:08:03.700
And they don't just exist in plants.

00:08:03.700 --> 00:08:06.058
They can also exist in animal cells.

00:08:06.058 --> 00:08:10.214
But in plant cells, they can
be very, very, very visible.

00:08:10.214 --> 00:08:12.107
Now, something that is somewhat related

00:08:12.107 --> 00:08:14.392
to some of the function
that a vacuole plays,

00:08:14.392 --> 00:08:16.115
that are most associated with animal cells

00:08:16.115 --> 00:08:17.249
but now there's evidence

00:08:17.249 --> 00:08:18.982
that they also exist in plant cells,

00:08:18.982 --> 00:08:20.956
is the idea of a lysosome.

00:08:20.956 --> 00:08:23.456
So a lysosome right over here,

00:08:24.880 --> 00:08:27.232
that also is a compartment.

00:08:27.232 --> 00:08:30.720
And it's going to contain a
whole series of enzymes in it

00:08:30.720 --> 00:08:34.247
that is useful for lysing, you could say,

00:08:34.247 --> 00:08:36.311
that is useful for breaking down

00:08:36.311 --> 00:08:39.171
either waste products as the cell lives,

00:08:39.171 --> 00:08:40.589
or even foreign substances

00:08:40.589 --> 00:08:42.771
that might not be helpful for the cells.

00:08:42.771 --> 00:08:45.031
So it's gonna contain a bunch of enzymes,

00:08:45.031 --> 00:08:47.346
and it helps break down things.

00:08:47.346 --> 00:08:48.971
Now, I'll leave you there.

00:08:48.971 --> 00:08:52.048
These aren't all of the
structures in eukaryotic cells,

00:08:52.048 --> 00:08:53.673
but these are enough of the structures

00:08:53.673 --> 00:08:54.962
so that you can appreciate

00:08:54.962 --> 00:08:58.509
that there are a lot of
membrane-bound organelles

00:08:58.509 --> 00:09:00.860
in eukaryotic cells.

00:09:00.860 --> 00:09:02.538
And to be clear, even if I were to show

00:09:02.538 --> 00:09:04.236
all of the membrane-bound structures,

00:09:04.236 --> 00:09:06.359
that's not all the complexity of the cell.

00:09:06.359 --> 00:09:07.579
The big thing to appreciate

00:09:07.579 --> 00:09:09.486
is that cells are incredibly complex.

00:09:09.486 --> 00:09:11.189
There's all sorts of structures in here

00:09:11.189 --> 00:09:14.234
that help transport things
and move things around.

00:09:14.234 --> 00:09:17.783
If you could shrink yourself
down and look inside of a cell,

00:09:17.783 --> 00:09:21.568
it would look more complex
than the most complex cities.

00:09:21.568 --> 00:09:23.449
There's all sorts of activities,

00:09:23.449 --> 00:09:25.659
things being moved
around, shuttled around.

00:09:25.659 --> 00:09:29.200
The cell itself is replicating
and copying things.

00:09:29.200 --> 00:09:31.162
And so this is just the beginning.

00:09:31.162 --> 00:09:33.110
We're just starting to scratch the surface

00:09:33.110 --> 00:09:37.193
of the complexity of the
most basic unit of life.


Introduction to the cell

WEBVTT
Kind: captions
Language: en

00:00:00.762 --> 00:00:02.877
- [Instructor] You might already
have some type of a notion

00:00:02.877 --> 00:00:04.400
of a what a cell is.

00:00:04.400 --> 00:00:08.691
You might already realize
that it is most basic unit

00:00:08.691 --> 00:00:10.096
of life.

00:00:10.096 --> 00:00:12.204
Some would argue that maybe viruses

00:00:12.204 --> 00:00:14.275
are even a more basic unit of life,

00:00:14.275 --> 00:00:17.360
but the organisms that we
consider living, like ourselves,

00:00:17.360 --> 00:00:20.209
are made up of cells
and all living organisms

00:00:20.209 --> 00:00:22.838
that we for sure consider
living are made up of at least

00:00:22.838 --> 00:00:26.255
one cell, so the most basic unit of life.

00:00:27.114 --> 00:00:30.279
For example, me, this thing
that's making a video right now,

00:00:30.279 --> 00:00:35.025
I'm made up of tens of
trillions of these cells.

00:00:35.025 --> 00:00:36.971
Now a common misconception is

00:00:36.971 --> 00:00:38.993
well these things must be small

00:00:38.993 --> 00:00:41.798
and they indeed are
very, very, very small.

00:00:41.798 --> 00:00:45.965
Some cells are on the order
of one micrometer long

00:00:46.872 --> 00:00:49.744
and a micrometer is
one-millionth of a meter,

00:00:49.744 --> 00:00:52.627
or you could just say
one-thousandth of a millimeter,

00:00:52.627 --> 00:00:54.637
and so when you think
of something that small,

00:00:54.637 --> 00:00:58.225
sometimes there's an assumption
that it must be simple,

00:00:58.225 --> 00:01:01.108
but you could not be
more wrong if you assume

00:01:01.108 --> 00:01:02.941
that a cell is simple.

00:01:03.778 --> 00:01:07.791
This right over here is a
picture of a budding yeast cell.

00:01:07.791 --> 00:01:10.187
You can see that it's
budding off right over here,

00:01:10.187 --> 00:01:13.744
but this just begins to show
you some of the complexity

00:01:13.744 --> 00:01:16.943
of the cell itself or of any cell,

00:01:16.943 --> 00:01:19.137
and whereas in other videos,
we're gonna talk about

00:01:19.137 --> 00:01:21.431
different types of cells,
different types of structures

00:01:21.431 --> 00:01:23.499
you'll see in some cells versus others,

00:01:23.499 --> 00:01:25.693
this right here is eukaryotic cell

00:01:25.693 --> 00:01:28.073
which we will talk more
about in other videos.

00:01:28.073 --> 00:01:31.793
Now all cells have a
membrane that separate it

00:01:31.793 --> 00:01:33.303
from the outside world.

00:01:33.303 --> 00:01:34.753
You see the membrane right over here.

00:01:34.753 --> 00:01:35.976
This is just a cross section.

00:01:35.976 --> 00:01:38.138
You could imagine a
three-dimensional version of this.

00:01:38.138 --> 00:01:41.055
So this is the cell, cell membrane.

00:01:43.949 --> 00:01:46.176
It kind of defines the cell in some way,

00:01:46.176 --> 00:01:49.480
and in general, the things
inside the cell membrane

00:01:49.480 --> 00:01:52.730
is considered the cytoplasm, cytoplasm.

00:01:55.582 --> 00:01:58.201
Sometimes you'll hear the term cytosol.

00:01:58.201 --> 00:02:00.757
The cytoplasm includes not just the fluid

00:02:00.757 --> 00:02:03.192
but also all of the stuff in the fluid

00:02:03.192 --> 00:02:07.829
while the cytosol is
referring to the fluid alone

00:02:07.829 --> 00:02:10.634
and then depending on
the complexity of a cell,

00:02:10.634 --> 00:02:12.181
so this is right here,
this is a yeast cell,

00:02:12.181 --> 00:02:14.847
this is a eukaryotic cell
which we cover in more depth

00:02:14.847 --> 00:02:18.065
in other videos but one of the
features of a eukaryotic cell

00:02:18.065 --> 00:02:21.115
is that you'll have a
membrane-bound nucleus.

00:02:21.115 --> 00:02:23.145
Now you see it in this
diagram right over here.

00:02:23.145 --> 00:02:25.850
This is not a common feature to all cells

00:02:25.850 --> 00:02:28.115
but the only reason why I'm
mentioning it in this video is

00:02:28.115 --> 00:02:32.708
officially, the cytoplasm does
not include the stuff inside

00:02:32.708 --> 00:02:34.294
the nucleus.

00:02:34.294 --> 00:02:37.086
In a eukaryotic cell, that
is called the nucleoplasm

00:02:37.086 --> 00:02:39.566
but we'll talk more about
that in other videos.

00:02:39.566 --> 00:02:42.532
Now another feature that
is common to all cells

00:02:42.532 --> 00:02:44.865
is the notion of a ribosome,

00:02:46.364 --> 00:02:49.892
and this picture is full of ribosomes.

00:02:49.892 --> 00:02:52.171
All of these little dots right
here, these little red dots,

00:02:52.171 --> 00:02:53.713
let me change my pen color,

00:02:53.713 --> 00:02:56.889
all of these little red dots
here, these are ribosomes,

00:02:56.889 --> 00:02:59.547
and you might assume,
"Wow. These are so small

00:02:59.547 --> 00:03:02.851
"compared to this already
small thing, this cell.

00:03:02.851 --> 00:03:04.374
"Surely they are simple,"

00:03:04.374 --> 00:03:07.659
but they're actually fairly complex RNA

00:03:07.659 --> 00:03:12.171
and protein structures, that
are, their main function is

00:03:12.171 --> 00:03:15.254
producing protein, producing protein.

00:03:16.552 --> 00:03:18.784
You can view these as
almost the protein factories

00:03:18.784 --> 00:03:19.841
of living organisms.

00:03:19.841 --> 00:03:23.133
They can take genetic
information in the form of RNA

00:03:23.133 --> 00:03:26.117
and produce proteins out
of them, and you can see

00:03:26.117 --> 00:03:28.712
this cell is full of ribosomes
and we're going to talk about

00:03:28.712 --> 00:03:32.352
the different types of
ribosomes in a future video.

00:03:32.352 --> 00:03:35.208
Now another thing that
is typical in most cells

00:03:35.208 --> 00:03:38.128
is genetic information, and typically,

00:03:38.128 --> 00:03:41.628
that genetic information is stored as DNA.

00:03:44.249 --> 00:03:46.193
Now I say in most cells
because it turns out

00:03:46.193 --> 00:03:48.722
that even in our bodies,
mature red blood cells

00:03:48.722 --> 00:03:51.323
don't have any DNA anymore
and there's other cells

00:03:51.323 --> 00:03:53.468
that do the same thing, but in general,

00:03:53.468 --> 00:03:56.117
in order for a cell to
function and replicate,

00:03:56.117 --> 00:03:59.432
it needs some genetic information
and that is stored in DNA,

00:03:59.432 --> 00:04:01.514
and that's true in both prokaryotic cells

00:04:01.514 --> 00:04:02.788
and eukaryotic cells.

00:04:02.788 --> 00:04:06.017
Prokaryotes are ones that don't
have a well-defined nucleus

00:04:06.017 --> 00:04:09.002
and membrane-bound what
we call organelles,

00:04:09.002 --> 00:04:10.733
which are these substructures in cells

00:04:10.733 --> 00:04:12.992
which we will talk more
about in other videos.

00:04:12.992 --> 00:04:15.761
In a prokaryotic cell, the
DNA is just floating around

00:04:15.761 --> 00:04:18.961
in the cytoplasm, while in
a eukaryotic cell, the DNA,

00:04:18.961 --> 00:04:22.601
for the most part, is
inside of your nucleus

00:04:22.601 --> 00:04:25.653
and it is part of the nucleoplasm.

00:04:25.653 --> 00:04:27.744
So I'll leave you there for now.

00:04:27.744 --> 00:04:30.694
The last thing I want you to
appreciate is just the scale.

00:04:30.694 --> 00:04:32.955
As I mentioned, cells are small.

00:04:32.955 --> 00:04:34.604
This picture of a yeast
cell right over here,

00:04:34.604 --> 00:04:39.030
this is a micrometer, on this
scale, it would be about,

00:04:39.030 --> 00:04:40.367
it would be about that.

00:04:40.367 --> 00:04:44.585
That would be one micrometer,
and to put that in context,

00:04:44.585 --> 00:04:46.146
the width of a human hair,

00:04:46.146 --> 00:04:49.186
and it actually depends on
your hair, whether it's soft

00:04:49.186 --> 00:04:51.619
or it's more like my hair
and it kind of sticks up

00:04:51.619 --> 00:04:53.176
and it's, you have thicker hair,

00:04:53.176 --> 00:04:55.441
but if this is a human
hair right over here,

00:04:55.441 --> 00:04:58.693
this is the width of a
human hair, this thing,

00:04:58.693 --> 00:05:02.776
its width is anywhere from
20 to 180 micrometers.

00:05:05.172 --> 00:05:09.100
My thick hair is probably
closer to 180 micrometers.

00:05:09.100 --> 00:05:11.478
So one way to think about
it, you could probably take

00:05:11.478 --> 00:05:14.811
20 or so of these yeast cells end to end

00:05:15.981 --> 00:05:17.849
and these yeast cells, these
aren't even the smallest cells

00:05:17.849 --> 00:05:20.886
by any stretch of the imagination,
and put them end to end,

00:05:20.886 --> 00:05:23.835
20 or 30 of these across one human hair

00:05:23.835 --> 00:05:26.350
and that's what's mind-blowing
because even at that scale,

00:05:26.350 --> 00:05:28.361
you have this complexity,

00:05:28.361 --> 00:05:30.943
and even this picture
doesn't do proper justice

00:05:30.943 --> 00:05:32.015
to the complexity.

00:05:32.015 --> 00:05:34.209
There's all sorts of
structures inside of this

00:05:34.209 --> 00:05:36.742
that you can't even see
that help transport things

00:05:36.742 --> 00:05:40.661
and move things around and
give the structure of the cell.

00:05:40.661 --> 00:05:42.106
So I'll leave you there.

00:05:42.106 --> 00:05:44.199
In future videos, we'll
dig a little bit more into

00:05:44.199 --> 00:05:47.375
what eukaryotic cells are,
what prokaryotic cells are.

00:05:47.375 --> 00:05:49.146
How do cells move around?

00:05:49.146 --> 00:05:51.244
How do they work together?


Introduction to passive and active transport

WEBVTT
Kind: captions
Language: en

00:00:00.703 --> 00:00:02.856
- [Instructor] Let's say
that you have decided to go

00:00:02.856 --> 00:00:06.403
canoeing, and right over
here, this is a top view of

00:00:06.403 --> 00:00:08.525
our river right here.

00:00:08.525 --> 00:00:09.418
This is our river.

00:00:09.418 --> 00:00:12.020
And, let's say that the
current, the river, is going

00:00:12.020 --> 00:00:14.030
towards the right.

00:00:14.030 --> 00:00:17.113
So, there is two different directions

00:00:17.985 --> 00:00:19.835
that you could be canoeing in.

00:00:19.835 --> 00:00:23.198
You could imagine someone
who is canoeing in the same

00:00:23.198 --> 00:00:27.331
direction as the current, so
they are canoeing that way.

00:00:27.331 --> 00:00:29.514
And then, you could imagine
another person who's canoeing

00:00:29.514 --> 00:00:30.959
the other way.

00:00:30.959 --> 00:00:33.314
So, someone who's canoeing upstream.

00:00:33.314 --> 00:00:34.799
This person is canoeing downstream,

00:00:34.799 --> 00:00:36.416
this person is canoeing upstream.

00:00:36.416 --> 00:00:38.618
So they are going in that direction.

00:00:38.618 --> 00:00:41.219
So, pause this video and
think about which person

00:00:41.219 --> 00:00:43.892
is going to have to expend more energy.

00:00:43.892 --> 00:00:46.278
Or, which person is going
to have to be more active,

00:00:46.278 --> 00:00:49.338
and which person is
going to be more passive.

00:00:49.338 --> 00:00:51.999
Well, yes, this wasn't an
incredibly hard question.

00:00:51.999 --> 00:00:54.803
If you are going with the flow of current,

00:00:54.803 --> 00:00:57.587
as the person in yellow is
here, they don't even have to

00:00:57.587 --> 00:00:58.683
take their paddles out.

00:00:58.683 --> 00:01:01.691
They can just take a nap,
and the boat will naturally

00:01:01.691 --> 00:01:03.223
go with the current.

00:01:03.223 --> 00:01:07.632
They would be, they could
be just moving passively.

00:01:07.632 --> 00:01:10.244
While the person in blue, here,
they're gonna have to work

00:01:10.244 --> 00:01:11.858
really, really, really hard.

00:01:11.858 --> 00:01:14.021
They're gonna have to paddle
some, just to not even move

00:01:14.021 --> 00:01:16.380
to the right, and then
even paddle even more,

00:01:16.380 --> 00:01:18.676
to actually go against the current.

00:01:18.676 --> 00:01:22.179
So, this person would
have to be very active.

00:01:22.179 --> 00:01:25.461
And so, this is really just
a metaphor for what we're

00:01:25.461 --> 00:01:26.832
going to talk about now.

00:01:26.832 --> 00:01:29.209
And, that's the idea in Biology of

00:01:29.209 --> 00:01:32.065
Active versus Passive Transport.

00:01:32.065 --> 00:01:35.253
So, let's start with, maybe,
the more pleasant one.

00:01:35.253 --> 00:01:36.576
In either situation.

00:01:36.576 --> 00:01:39.159
And that is, Passive Transport.

00:01:40.476 --> 00:01:43.829
So, Passive Transport is when something

00:01:43.829 --> 00:01:45.663
goes with the gradient.

00:01:45.663 --> 00:01:47.033
So what do I mean by that?

00:01:47.033 --> 00:01:49.896
So, you could have a
concentration gradient.

00:01:49.896 --> 00:01:54.792
So, let's say that on, let's
say I have a tube of some kind.

00:01:54.792 --> 00:01:57.000
And let's say it's filled with water.

00:01:57.000 --> 00:01:59.416
And dissolved in that water,
at this end of the tube,

00:01:59.416 --> 00:02:03.166
I have a high concentration
of some molecule,

00:02:04.335 --> 00:02:05.744
or something right over here.

00:02:05.744 --> 00:02:08.265
While on the right-hand side
I have a low concentration.

00:02:08.265 --> 00:02:10.836
So what are we think is going to happen?

00:02:10.836 --> 00:02:13.466
Well, these things are just
going to naturally move around,

00:02:13.466 --> 00:02:16.972
and over time, they're gonna
bounce their way, so that after

00:02:16.972 --> 00:02:19.593
a little bit of time has passed,
a lot of these things are

00:02:19.593 --> 00:02:23.737
just going to passively move to the right.

00:02:23.737 --> 00:02:26.487
And so at some point, you might
have an equal concentration,

00:02:26.487 --> 00:02:30.097
or roughly equal, throughout
this entire container.

00:02:30.097 --> 00:02:33.713
And so, this movement along
your concentration gradient...

00:02:33.713 --> 00:02:35.685
Here you're moving from
high-concentration,

00:02:35.685 --> 00:02:40.033
to low-concentration, this
would be passive transport.

00:02:40.033 --> 00:02:43.516
This is a concentration gradient,
that we are moving along.

00:02:43.516 --> 00:02:45.017
Let me write that down.

00:02:45.017 --> 00:02:47.327
This is our concentration gradient.

00:02:47.327 --> 00:02:49.968
But, you can also have
an electrical gradient.

00:02:49.968 --> 00:02:53.551
So, let's take a similar
type of container.

00:02:54.539 --> 00:02:57.809
Maybe it's filled with water,
and on the left-hand side,

00:02:57.809 --> 00:02:59.923
imagine if you have a bunch of

00:02:59.923 --> 00:03:02.594
positive particles, or molecules.

00:03:02.594 --> 00:03:04.524
And on the right, you have a bunch of

00:03:04.524 --> 00:03:07.725
negative particles, or molecules.

00:03:07.725 --> 00:03:09.806
Well, the positive ones repel each other,

00:03:09.806 --> 00:03:11.118
so do the negative ones.

00:03:11.118 --> 00:03:13.403
But the positives attract the negative,

00:03:13.403 --> 00:03:15.292
and the negative attract the positive.

00:03:15.292 --> 00:03:18.197
And so, you would think that
things would naturally move

00:03:18.197 --> 00:03:19.965
down their electrical gradient.

00:03:19.965 --> 00:03:21.887
The positives want to
go away from each other,

00:03:21.887 --> 00:03:24.406
and they're drawn to the negative.

00:03:24.406 --> 00:03:26.690
Similarly, the negatives wanna
get away from each other,

00:03:26.690 --> 00:03:28.925
and they are drawn to the positive.

00:03:28.925 --> 00:03:31.362
So, whether you're talking
about a concentration gradient,

00:03:31.362 --> 00:03:32.634
or an electrical gradient...

00:03:32.634 --> 00:03:34.260
And sometimes you have
a combination of both.

00:03:34.260 --> 00:03:35.865
An electro-chemical gradient.

00:03:35.865 --> 00:03:38.059
When you're moving along
with your gradient,

00:03:38.059 --> 00:03:39.734
you don't have to use any energy.

00:03:39.734 --> 00:03:42.233
That's known as Passive Transport.

00:03:42.233 --> 00:03:43.983
So, no energy needed.

00:03:48.714 --> 00:03:51.448
It's just going to happen naturally.

00:03:51.448 --> 00:03:55.622
Now, the opposite is the
notion of Active Transport.

00:03:55.622 --> 00:03:58.803
Active Transport, and this is when you

00:03:58.803 --> 00:04:00.896
go against the gradient.

00:04:00.896 --> 00:04:03.729
So an Active Transport would
be, somehow let's say you're in

00:04:03.729 --> 00:04:05.618
this situation right over here,

00:04:05.618 --> 00:04:08.402
somehow getting one of these particles...

00:04:08.402 --> 00:04:10.364
Let me do it in the same color,
somehow getting one of these

00:04:10.364 --> 00:04:13.522
particles, instead moving
to go in that direction.

00:04:13.522 --> 00:04:15.281
It will actually go against it's gradient,

00:04:15.281 --> 00:04:16.520
in that direction.

00:04:16.520 --> 00:04:19.394
Or, another situation is,
imagine if you have a positive

00:04:19.394 --> 00:04:23.266
particle right over here,
instead of it naturally just

00:04:23.266 --> 00:04:25.588
going in that direction,
somehow you make it go against

00:04:25.588 --> 00:04:27.776
it's gradient, and you make it go closer

00:04:27.776 --> 00:04:29.828
to the other positive particles.

00:04:29.828 --> 00:04:33.495
Well, this is going to
require energy to do.

00:04:34.916 --> 00:04:37.761
And probably the most sited
example, or the most common

00:04:37.761 --> 00:04:40.199
example that we're going
to see, in Biology class,

00:04:40.199 --> 00:04:42.027
of Active Transport,

00:04:42.027 --> 00:04:44.486
is what's known as a
sodium-potassium pump.

00:04:44.486 --> 00:04:47.198
Which we will study in
detail in other videos.

00:04:47.198 --> 00:04:49.403
But, let's say that this
thing that I'm drawing,

00:04:49.403 --> 00:04:52.653
here in white, this is a cell membrane.

00:04:53.526 --> 00:04:56.403
And, I'm drawing these gaps for a reason.

00:04:56.403 --> 00:05:00.570
And, what you have on the
outside of the cell membrane,

00:05:01.442 --> 00:05:05.609
you have some potassium
ions, on the outside, but,

00:05:06.519 --> 00:05:09.346
you have a lot more on the inside.

00:05:09.346 --> 00:05:13.436
So, these are all potassium
ions on the inside of your cell.

00:05:13.436 --> 00:05:17.603
And then, so let me just
write K+, K+, K+, K+, K+,

00:05:20.419 --> 00:05:23.243
and you'll have some
sodium ions on the inside

00:05:23.243 --> 00:05:24.949
of your cell;

00:05:24.949 --> 00:05:29.116
Na+, but you have a lot more
on the outside of your cell.

00:05:30.058 --> 00:05:31.735
And, in general, the outside
of your cell is going to have

00:05:31.735 --> 00:05:35.128
many more positive ions than the inside.

00:05:35.128 --> 00:05:38.887
Maybe you already see where this is going.

00:05:38.887 --> 00:05:43.054
Na+, Na+, Na+, I think we've
got the idea, Na+, Na+.

00:05:46.535 --> 00:05:49.522
Now, if on this membrane,
alright, let's ignore this part

00:05:49.522 --> 00:05:52.346
right over here, if I just had
a channel, right over here,

00:05:52.346 --> 00:05:55.677
that was open only to potassium.

00:05:55.677 --> 00:05:58.502
So, only potassium can go through.

00:05:58.502 --> 00:06:01.669
So, only potassium can go through this

00:06:03.248 --> 00:06:04.293
channel right over here.

00:06:04.293 --> 00:06:06.356
What do you think is going to happen?

00:06:06.356 --> 00:06:08.630
Well, you would have Passive Transport.

00:06:08.630 --> 00:06:11.688
These positively charged
potassiums right over here,

00:06:11.688 --> 00:06:14.542
they would go down their
concentration gradient.

00:06:14.542 --> 00:06:17.653
There's more likely to have
a potassium ion just bump

00:06:17.653 --> 00:06:20.201
in the right way, just right
over here, so that it goes

00:06:20.201 --> 00:06:21.034
through the channel.

00:06:21.034 --> 00:06:23.084
Because, there's just more
potassiums right on the

00:06:23.084 --> 00:06:25.971
inside of the cell, than
there would be on the outside.

00:06:25.971 --> 00:06:27.759
And so, this, this potassium

00:06:27.759 --> 00:06:29.649
is going down their
concentration gradient,

00:06:29.649 --> 00:06:31.895
from high-concentration,
to low-concentration

00:06:31.895 --> 00:06:33.101
through this channel.

00:06:33.101 --> 00:06:35.785
This would be Passive Transport.

00:06:35.785 --> 00:06:37.285
Passive Transport.

00:06:39.422 --> 00:06:42.550
But, you could imagine
there's also Active Transport,

00:06:42.550 --> 00:06:46.198
and that Active Transport is
what pumps the sodium ions

00:06:46.198 --> 00:06:49.754
inside the cell outside of
the cell, even thought it's

00:06:49.754 --> 00:06:52.415
not only against it's
concentration gradient,

00:06:52.415 --> 00:06:54.599
it's also against it's
electrical gradient.

00:06:54.599 --> 00:06:56.845
The outside's more positive,
so you wouldn't think a

00:06:56.845 --> 00:06:59.412
positive ion would naturally go outside.

00:06:59.412 --> 00:07:02.401
And the outside has more
sodiums that it does inside.

00:07:02.401 --> 00:07:04.382
But, the sodium-potassium pump

00:07:04.382 --> 00:07:07.065
still pumps those sodiums outside.

00:07:07.065 --> 00:07:09.846
And, as I hinted at, it
does this using energy.

00:07:09.846 --> 00:07:12.580
So, you'll sometimes see a
sodium-potassium pump drawn

00:07:12.580 --> 00:07:16.594
like this and, once again
I'm not gonna go into depth

00:07:16.594 --> 00:07:20.251
on it, we have a whole video on it.

00:07:20.251 --> 00:07:22.657
But, the general idea
is, is that the sodiums

00:07:22.657 --> 00:07:23.907
bind over here.

00:07:24.750 --> 00:07:27.687
And then some ATP, which
is the powerhouse of cells;

00:07:27.687 --> 00:07:30.450
which we will study in more
depth later on in Biology,

00:07:30.450 --> 00:07:35.245
it leverages it's energy to
change the shape of the proteins

00:07:35.245 --> 00:07:37.692
that make up this sodium potassium pump,

00:07:37.692 --> 00:07:41.957
to then pump these sodiums
outside of the cell.

00:07:41.957 --> 00:07:43.726
So, it's gonna go from
this shape, and then

00:07:43.726 --> 00:07:46.002
it's just going to, you
could view it as opening

00:07:46.002 --> 00:07:49.883
it up that way, the real
enzymes look quite different,

00:07:49.883 --> 00:07:51.569
but that's the general idea.

00:07:51.569 --> 00:07:55.736
You use energy, in the form
of ATP to pump the sodiums out

00:07:57.258 --> 00:08:00.294
against both their concentration gradient,

00:08:00.294 --> 00:08:02.268
and their electrical gradient.

00:08:02.268 --> 00:08:05.502
And that's why it's
called Active Transport.


Introduction to pH

WEBVTT
Kind: captions
Language: en

00:00:00.226 --> 00:00:01.112
- [Instructor] What we're
going to do in this video

00:00:01.112 --> 00:00:02.961
is talk about acidity and in particular,

00:00:02.961 --> 00:00:06.187
we're gonna talk about the pH scale.

00:00:06.187 --> 00:00:09.552
Now the first question
is what does pH stand for

00:00:09.552 --> 00:00:11.613
and it turns out that there's some debate

00:00:11.613 --> 00:00:14.285
why we have this lowercase p here,

00:00:14.285 --> 00:00:16.095
we know why we have the h,

00:00:16.095 --> 00:00:17.787
and some people will tell you it stands

00:00:17.787 --> 00:00:22.717
for power of hydrogen, the
capital h for hydrogen.

00:00:22.717 --> 00:00:26.884
Some people will say it's
the potential of hydrogen.

00:00:27.867 --> 00:00:32.034
Some people will say it's
the capacity for hydrogen,

00:00:33.028 --> 00:00:35.803
you might say capacity
doesn't start with a p

00:00:35.803 --> 00:00:37.983
but if you go into Latin, it can.

00:00:37.983 --> 00:00:39.915
But what do all of these things mean

00:00:39.915 --> 00:00:43.137
and why do we care about hydrogen so much?

00:00:43.137 --> 00:00:45.400
Well, it turns out that
hydrogen, and in particular,

00:00:45.400 --> 00:00:48.034
a hydrogen positive ion, and ion

00:00:48.034 --> 00:00:50.655
is just a positively charged molecule,

00:00:50.655 --> 00:00:53.061
that a hydrogen ion can play a major role

00:00:53.061 --> 00:00:55.917
in how acidic or basic something is.

00:00:55.917 --> 00:00:58.192
And so the pH scale, you're gonna see it

00:00:58.192 --> 00:01:00.692
go from zero all the way to 14

00:01:03.597 --> 00:01:06.938
with of course, seven in the middle,

00:01:06.938 --> 00:01:09.617
and something that is towards the left,

00:01:09.617 --> 00:01:13.460
something that is less than
seven is considered acidic,

00:01:13.460 --> 00:01:15.042
and so if you have a pH near zero

00:01:15.042 --> 00:01:17.337
that is highly, highly, highly acidic,

00:01:17.337 --> 00:01:21.494
while something to the
right is considered basic

00:01:21.494 --> 00:01:25.961
and something in the middle
is considered neutral.

00:01:25.961 --> 00:01:28.178
And another term for
basic you'll sometimes see

00:01:28.178 --> 00:01:31.946
is alkaline, and alkaline
actually comes from Arabic

00:01:31.946 --> 00:01:35.777
for alkali which was the word
that ancient Arab chemists use

00:01:35.777 --> 00:01:39.933
for a compound that
happens to be very basic

00:01:39.933 --> 00:01:42.116
by our modern definition.

00:01:42.116 --> 00:01:44.299
But what does it mean to be acidic

00:01:44.299 --> 00:01:45.945
and what does it mean to be basic

00:01:45.945 --> 00:01:49.521
and once again, how does that
connect with hydrogen ions?

00:01:49.521 --> 00:01:51.209
Well, it turns out, and
I'm not gonna go in depth

00:01:51.209 --> 00:01:54.264
in this video, is that
things that are acidic

00:01:54.264 --> 00:01:57.097
tend to have lots of hydrogen ions

00:01:59.255 --> 00:02:03.136
and while things that
are basic tend to react,

00:02:03.136 --> 00:02:06.436
react with these hydrogen ions.

00:02:06.436 --> 00:02:08.886
There's other definitions
for what it means

00:02:08.886 --> 00:02:10.720
to be an acid or base
and we'll go into depth

00:02:10.720 --> 00:02:13.233
in chemistry class on that,

00:02:13.233 --> 00:02:17.000
but this is why it's
connected with the term pH.

00:02:17.000 --> 00:02:19.905
Now what are examples of
things that are acidic?

00:02:19.905 --> 00:02:21.856
Well, you see it on this
chart right over here.

00:02:21.856 --> 00:02:23.616
Here, we're going in
the vertical direction.

00:02:23.616 --> 00:02:26.194
Things in our everyday
life that are quite acidic,

00:02:26.194 --> 00:02:28.248
a lot of fruits are quite acidic,

00:02:28.248 --> 00:02:30.218
for example, lemons and grapefruits

00:02:30.218 --> 00:02:33.185
and orange juice are quite acidic.

00:02:33.185 --> 00:02:34.920
They're at the low end of the scale.

00:02:34.920 --> 00:02:37.046
And some of the telltale signs for acidity

00:02:37.046 --> 00:02:39.696
is if you were to drink it or eat it,

00:02:39.696 --> 00:02:43.475
that it would have this kind
of sharp sour taste to it,

00:02:43.475 --> 00:02:46.400
while if you go to the
other end of the spectrum,

00:02:46.400 --> 00:02:49.846
things that are basic, these
would be things like bleaches

00:02:49.846 --> 00:02:52.170
and ammonia solution and we can even go

00:02:52.170 --> 00:02:55.137
super basic to liquid drain cleaner,

00:02:55.137 --> 00:02:59.210
and these are going to have
more of a slimy texture to it.

00:02:59.210 --> 00:03:01.282
In fact, even soap is quite basic.

00:03:01.282 --> 00:03:03.498
And of the basic things
that you could eat,

00:03:03.498 --> 00:03:07.755
you might have a bitter
taste associated with it.

00:03:07.755 --> 00:03:09.941
But to be clear, I really don't recommend

00:03:09.941 --> 00:03:13.494
eating or drinking anything
that is either highly basic

00:03:13.494 --> 00:03:15.940
or highly acidic, and the reason is

00:03:15.940 --> 00:03:19.143
is that things that are at
the extreme of the pH scale,

00:03:19.143 --> 00:03:22.233
so things that are either extremely basic

00:03:22.233 --> 00:03:25.150
or things that are extremely acidic

00:03:26.012 --> 00:03:29.321
like battery acid or hydrochloric acid,

00:03:29.321 --> 00:03:32.807
because they're so reactive,
they will damage you.

00:03:32.807 --> 00:03:34.940
If you pour it in your
skin, it will damage you.

00:03:34.940 --> 00:03:38.200
If you ingest it, it
will damage your cells

00:03:38.200 --> 00:03:39.918
and it can even kill you.

00:03:39.918 --> 00:03:42.507
So don't try to taste things to see

00:03:42.507 --> 00:03:44.517
whether they're acid or
basic, and if you do,

00:03:44.517 --> 00:03:46.012
try to make sure that they're closer

00:03:46.012 --> 00:03:49.095
to this middle range of our pH scale.

00:03:50.370 --> 00:03:52.259
So I've talked a lot about
things that are acidic

00:03:52.259 --> 00:03:54.587
or basic, but also what's interesting

00:03:54.587 --> 00:03:57.216
is things that we consider to be neutral.

00:03:57.216 --> 00:04:00.386
So our blood, for
example, is quite neutral,

00:04:00.386 --> 00:04:02.763
and this is something
that doctors might measure

00:04:02.763 --> 00:04:05.750
because if your pH in your
blood gets a little bit too high

00:04:05.750 --> 00:04:06.583
or a little bit too low,

00:04:06.583 --> 00:04:08.705
that can cause some serious problems.

00:04:08.705 --> 00:04:11.735
Sea water is pretty
close to being neutral.

00:04:11.735 --> 00:04:15.006
Milk is not that far off of being neutral.

00:04:15.006 --> 00:04:17.064
Now with that said, in order to read

00:04:17.064 --> 00:04:20.004
the pH scale appropriately
or appreciate the differences

00:04:20.004 --> 00:04:23.011
in acidity and basicity,
it's important to realize

00:04:23.011 --> 00:04:25.255
that it is not a linear scale.

00:04:25.255 --> 00:04:28.851
So for example, something
that has a pH of eight

00:04:28.851 --> 00:04:33.319
is not twice as basic as
something that has a pH of four.

00:04:33.319 --> 00:04:35.290
It turns out, when you go
form one level of our pH scale

00:04:35.290 --> 00:04:39.265
to the other, you are
going up in basicity,

00:04:39.265 --> 00:04:42.098
say going from a pH four to a pH of five,

00:04:42.098 --> 00:04:43.610
by a factor of 10.

00:04:43.610 --> 00:04:45.671
And so, comparing
something with a pH of four

00:04:45.671 --> 00:04:47.819
to a pH of eight, that
thing with the pH of four

00:04:47.819 --> 00:04:49.819
would be 10, 100, 1,000,

00:04:51.862 --> 00:04:53.934
10,000 times more acidic,

00:04:53.934 --> 00:04:56.009
or you could say the
thing with a pH of eight

00:04:56.009 --> 00:04:57.509
is 10, 100, 1,000,

00:04:58.822 --> 00:05:00.822
10,000 times more basic.

00:05:02.276 --> 00:05:03.556
So I'll leave you there.

00:05:03.556 --> 00:05:06.522
Keep a lookout when people
talk about pH balance

00:05:06.522 --> 00:05:09.184
or blood pH, and we're also, as we study

00:05:09.184 --> 00:05:11.134
more and more biology,
we're gonna talk about

00:05:11.134 --> 00:05:14.365
how pH might influence
some biological reactions

00:05:14.365 --> 00:05:16.672
and especially once
you get into chemistry,

00:05:16.672 --> 00:05:20.839
pH will inform us what type of
reaction is likely to happen.


Introduction to vitamins and minerals

WEBVTT
Kind: captions
Language: en

00:00:00.501 --> 00:00:02.091
- [Instructor] We've been
told throughout out lives

00:00:02.091 --> 00:00:06.115
to eat certain foods because
they contain vitamins

00:00:06.115 --> 00:00:08.436
or sometimes people might
say they also contain

00:00:08.436 --> 00:00:10.637
some minerals that you need,

00:00:10.637 --> 00:00:13.749
and so the obvious question
is, well what are vitamins?

00:00:13.749 --> 00:00:16.942
And what are these minerals
that folks are talking about?

00:00:16.942 --> 00:00:19.474
Well the big picture idea is,
that there's certain things

00:00:19.474 --> 00:00:21.969
that your body needs and
we'll talk in a second

00:00:21.969 --> 00:00:24.605
about why your body needs these things,

00:00:24.605 --> 00:00:26.516
but also, there are things
that your body needs

00:00:26.516 --> 00:00:28.536
and your body does not produce them.

00:00:28.536 --> 00:00:30.369
Body does not produce.

00:00:33.360 --> 00:00:35.068
There's a lot of things
your body needs that

00:00:35.068 --> 00:00:37.311
your body is capable of producing
but there's certain things

00:00:37.311 --> 00:00:39.941
that it needs that it
cannot produce itself.

00:00:39.941 --> 00:00:42.058
Now if these things that they need,

00:00:42.058 --> 00:00:44.334
that the body needs and it cannot produce,

00:00:44.334 --> 00:00:46.001
if they are organic,

00:00:47.459 --> 00:00:49.673
and organic is just a very fancy way

00:00:49.673 --> 00:00:51.439
of saying if there are compounds

00:00:51.439 --> 00:00:53.274
that involve carbons in them,

00:00:53.274 --> 00:00:56.981
and most molecules in life
involve a lot of carbons,

00:00:56.981 --> 00:00:59.211
that's why they're
called organic molecules.

00:00:59.211 --> 00:01:00.905
There's a whole field of chemistry,

00:01:00.905 --> 00:01:04.014
of organic chemistry which
is studying the chemistry

00:01:04.014 --> 00:01:06.319
of life for the most part.

00:01:06.319 --> 00:01:09.273
If these molecules, if these
things that the body needs

00:01:09.273 --> 00:01:11.263
that it does not produce,
itself are organic,

00:01:11.263 --> 00:01:13.763
we call these things vitamins.

00:01:15.286 --> 00:01:18.441
And some of the common vitamins
that you'll hear people

00:01:18.441 --> 00:01:22.405
talk about are things
like Vitamin A, Vitamin D,

00:01:22.405 --> 00:01:26.572
Vitamin E, Vitamin K, Vitamin
C, and you can further divide

00:01:28.593 --> 00:01:31.861
these vitamins based on
whether they are soluble

00:01:31.861 --> 00:01:33.367
in fat or not.

00:01:33.367 --> 00:01:37.486
So, for example, Vitamins A, D, E and K,

00:01:37.486 --> 00:01:40.885
and this is by no means an
exhaustive list of vitamins,

00:01:40.885 --> 00:01:43.337
these are fat soluble.

00:01:43.337 --> 00:01:44.375
What does that mean?

00:01:44.375 --> 00:01:46.044
Well, to be soluble means you could be

00:01:46.044 --> 00:01:47.146
dissolved in that thing.

00:01:47.146 --> 00:01:49.108
So it can be dissolved in fat.

00:01:49.108 --> 00:01:51.691
And Vitamin C is water soluble.

00:01:54.164 --> 00:01:57.429
Now the reason why this
might be relevant for you,

00:01:57.429 --> 00:01:59.617
living as an individual,
trying to keep your health

00:01:59.617 --> 00:02:03.054
in good shape, is that you do
need all of these vitamins,

00:02:03.054 --> 00:02:05.440
and we'll talk in a little
bit about why you need them,

00:02:05.440 --> 00:02:08.039
but fat soluble vitamins,
they're actually easier

00:02:08.039 --> 00:02:10.656
to overdose on, because
they're soluble in fat,

00:02:10.656 --> 00:02:12.548
they can stay in your system a lot longer,

00:02:12.548 --> 00:02:15.007
while water soluble vitamins are easier

00:02:15.007 --> 00:02:17.532
to flush out of your system.

00:02:17.532 --> 00:02:19.270
Now, with that out of the
way, let's think about some

00:02:19.270 --> 00:02:21.271
of these common foods you might see,

00:02:21.271 --> 00:02:24.990
and some of the vitamins
that they are known for.

00:02:24.990 --> 00:02:27.306
For example, right over
here you have carrots,

00:02:27.306 --> 00:02:28.634
and you might have had people tell you,

00:02:28.634 --> 00:02:29.574
"Hey, eat carrots.

00:02:29.574 --> 00:02:31.066
"It's good for your eyes."

00:02:31.066 --> 00:02:32.887
And that is true, but the reason why

00:02:32.887 --> 00:02:33.834
it's good for your eyes,

00:02:33.834 --> 00:02:38.409
is that carrots contain
something known as betacarotene,

00:02:38.409 --> 00:02:42.534
and the carotene part of
betacarotene is not a coincidence.

00:02:42.534 --> 00:02:45.157
It literally comes from Latin for carrot,

00:02:45.157 --> 00:02:47.754
and carotenes are these pigment molecules.

00:02:47.754 --> 00:02:50.489
It gives the carrot this
orange color right over here,

00:02:50.489 --> 00:02:53.826
and betacarotene, once
it's consumed by your body,

00:02:53.826 --> 00:02:56.409
it's a precursor for Vitamin A,

00:02:58.003 --> 00:02:59.584
which is essential for your eyes

00:02:59.584 --> 00:03:02.021
and many, many other things in your body.

00:03:02.021 --> 00:03:04.517
And a precursor's just a
very fancy way of saying

00:03:04.517 --> 00:03:08.263
that if you consume
betacarotene, you're body can

00:03:08.263 --> 00:03:11.690
turn it into the Vitamin A that it needs.

00:03:11.690 --> 00:03:15.108
Oranges, famous for
Vitamin C, and this isn't

00:03:15.108 --> 00:03:17.921
an exhaustive list of things
that these foods contain,

00:03:17.921 --> 00:03:20.538
but this is some of the things
that they're most famous for,

00:03:20.538 --> 00:03:24.330
and Vitamin C as we talked about
is a water soluble vitamin.

00:03:24.330 --> 00:03:26.878
It's very valuable for immune system,

00:03:26.878 --> 00:03:29.591
and in a situation where
you have a severe deficiency

00:03:29.591 --> 00:03:34.430
of Vitamin C, you could get
a disease known as scurvy.

00:03:34.430 --> 00:03:37.148
And scurvy is not too common
anymore, but several hundred

00:03:37.148 --> 00:03:40.020
years ago, sailors would
often get scurvy because

00:03:40.020 --> 00:03:41.483
they had very limited diets.

00:03:41.483 --> 00:03:43.470
They did not get fruits and vegetables,

00:03:43.470 --> 00:03:45.792
and because of that Vitamin C deficiency,

00:03:45.792 --> 00:03:48.412
their collagen, their connective
tissue would break down.

00:03:48.412 --> 00:03:52.841
So it was a very horrible
and painful disease.

00:03:52.841 --> 00:03:54.472
But what if there's
something your body needs

00:03:54.472 --> 00:03:57.220
that it does not produce
that is not organic?

00:03:57.220 --> 00:04:01.508
Well those are the things
that we call minerals.

00:04:01.508 --> 00:04:03.392
And, of course, the term
minerals, it's also used

00:04:03.392 --> 00:04:05.399
in a geological sense, but
if were talking in terms

00:04:05.399 --> 00:04:07.426
of biology, that's what we mean.

00:04:07.426 --> 00:04:10.978
And most of the typical
minerals are really elements

00:04:10.978 --> 00:04:13.660
that you will see on the periodic table.

00:04:13.660 --> 00:04:16.302
They will be things like phosphorous,

00:04:16.302 --> 00:04:19.023
and I'm just gonna write
their element symbol.

00:04:19.023 --> 00:04:23.106
Phosphorous, calcium,
potassium, magnesium, iron,

00:04:25.920 --> 00:04:27.987
and again, this is not an exhaustive list,

00:04:27.987 --> 00:04:30.886
but these are all essential for your body.

00:04:30.886 --> 00:04:33.776
As we go further in our study of biology,

00:04:33.776 --> 00:04:36.207
you will see how phosphorous is useful

00:04:36.207 --> 00:04:39.658
in molecules like ATP, the energy store.

00:04:39.658 --> 00:04:43.829
It's even in the backbone of DNA and RNA.

00:04:43.829 --> 00:04:47.836
We'll see how calcium is
useful, not just for your bones,

00:04:47.836 --> 00:04:50.365
but even for things like
muscle contractions.

00:04:50.365 --> 00:04:53.308
To send signals down
neurons, you're going to need

00:04:53.308 --> 00:04:55.598
your potassium and also sodium.

00:04:55.598 --> 00:04:59.257
Magnesium, also important
for muscle contraction.

00:04:59.257 --> 00:05:02.840
Iron, this is in your
hemoglobin, bonds to the oxygen,

00:05:02.840 --> 00:05:05.429
allows you to transport
oxygen in your bloodstream

00:05:05.429 --> 00:05:06.875
and red blood cells.

00:05:06.875 --> 00:05:09.001
So these are all very valuable.

00:05:09.001 --> 00:05:11.126
And a lot of those foods
that we just talked about

00:05:11.126 --> 00:05:14.400
that contain vitamins,
they'll also contain minerals.

00:05:14.400 --> 00:05:18.970
For example, not only do
carrots contain betacarotene,

00:05:18.970 --> 00:05:22.627
they also contain potassium,
which we mentioned

00:05:22.627 --> 00:05:27.079
is essential for things
like nerve function.

00:05:27.079 --> 00:05:30.340
Things like milk, it has
vitamins, like Vitamin D,

00:05:30.340 --> 00:05:33.288
but it also has minerals like calcium,

00:05:33.288 --> 00:05:35.581
which we talked about as
essential for your bones

00:05:35.581 --> 00:05:37.729
and for muscle function.

00:05:37.729 --> 00:05:39.200
And so the big picture here is,

00:05:39.200 --> 00:05:41.761
is that vitamins and
minerals are both things

00:05:41.761 --> 00:05:44.661
that your body needs, that
it does not produce itself,

00:05:44.661 --> 00:05:47.245
and we're going to see them
over and over again in biology.

00:05:47.245 --> 00:05:48.887
So keep a lookout for them.

00:05:48.887 --> 00:05:51.394
The vitamins as we go further
in our study of biology,

00:05:51.394 --> 00:05:53.494
we're going to see them as co-enzymes,

00:05:53.494 --> 00:05:56.330
things that help facilitate
functions of the cell,

00:05:56.330 --> 00:05:58.825
help facilitate reactions and the minerals

00:05:58.825 --> 00:06:01.442
you're going to see in
everything from the powerhouse

00:06:01.442 --> 00:06:03.949
of the cell, the backbone of DNA,

00:06:03.949 --> 00:06:05.936
you're going to see it
in muscle contraction

00:06:05.936 --> 00:06:07.183
and how bones are formed.

00:06:07.183 --> 00:06:08.787
You're gonna see it in hemoglobin.

00:06:08.787 --> 00:06:10.610
You're gonna see it in nerve function.


Probability of sample proportions example

WEBVTT
Kind: captions
Language: en

00:00:00.644 --> 00:00:04.292
- [Instructor] We're told
suppose that 15% of the 1,750

00:00:04.292 --> 00:00:08.585
students at a school have
experienced extreme levels

00:00:08.585 --> 00:00:10.643
of stress during the past month.

00:00:10.643 --> 00:00:13.844
A high school newspaper doesn't
know this figure, but they

00:00:13.844 --> 00:00:17.865
are curious what it is, so
they decide to ask a simple

00:00:17.865 --> 00:00:21.824
random sample of 160 students
if they have experienced

00:00:21.824 --> 00:00:25.523
extreme levels of stress
during the past month.

00:00:25.523 --> 00:00:30.160
Subsequently, they find that
10% of the sample replied "yes"

00:00:30.160 --> 00:00:32.203
to the question.

00:00:32.203 --> 00:00:36.313
Assuming the true proportion
is 15%, which they tell us

00:00:36.313 --> 00:00:40.632
up here, they say 15% of
the population of the 1,750

00:00:40.632 --> 00:00:44.487
students actually have experienced
extreme levels of stress

00:00:44.487 --> 00:00:46.899
during the past month, so
that is the true proportion,

00:00:46.899 --> 00:00:48.942
so let me just write that,
the true proportion for our

00:00:48.942 --> 00:00:52.723
population is 0.15, what is
the approximate probability

00:00:52.723 --> 00:00:56.890
that more than 10% of the
sample would report that they

00:01:00.631 --> 00:01:04.798
experienced extreme levels of
stress during the past month.

00:01:06.241 --> 00:01:08.180
So pause this video and see
if you can answer it on your

00:01:08.180 --> 00:01:10.835
own and there are four
choices here I'll scroll down

00:01:10.835 --> 00:01:14.577
a little bit and see if you
can answer this on your own.

00:01:14.577 --> 00:01:16.609
So the way that we're going
to tackle this is we're

00:01:16.609 --> 00:01:20.776
going to think about the
sampling distribution of our

00:01:21.622 --> 00:01:25.604
sample proportions and first
we're going to say well

00:01:25.604 --> 00:01:29.499
is this sampling distribution
approximately normal,

00:01:29.499 --> 00:01:33.666
is it approximately normal
and if it is, then we can use

00:01:36.443 --> 00:01:39.984
its mean and the standard
deviation and create a normal

00:01:39.984 --> 00:01:43.340
distribution that has that same
mean and standard deviation

00:01:43.340 --> 00:01:45.770
in order to approximate the
probability that they're

00:01:45.770 --> 00:01:46.940
asking for.

00:01:46.940 --> 00:01:50.365
So first this first part,
how do we decide this?

00:01:50.365 --> 00:01:52.875
Well the rule of thumb we
have here and it is a rule

00:01:52.875 --> 00:01:56.251
of thumb, is that if we take
our sample size times our

00:01:56.251 --> 00:01:59.737
population proportion and that
is greater than or equal to

00:01:59.737 --> 00:02:03.904
ten and our sample size times
one minus our population

00:02:05.310 --> 00:02:09.275
proportion is greater than
or equal to ten, then if both

00:02:09.275 --> 00:02:11.579
of these are true then our
sampling distribution of our

00:02:11.579 --> 00:02:15.259
sample proportions is going
to be approximately normal.

00:02:15.259 --> 00:02:17.707
So in this case the newspaper
is asking 160 students,

00:02:17.707 --> 00:02:21.874
that's the sample size, so
160, the true population

00:02:22.713 --> 00:02:26.939
proportion is 0.15 and that
needs to be greater than

00:02:26.939 --> 00:02:30.248
or equal to ten and so let's
see this is going to be 16

00:02:30.248 --> 00:02:34.415
plus eight which is 24 and
24 is indeed greater than

00:02:35.495 --> 00:02:38.443
or equal to ten so that
checks out and then if I take

00:02:38.443 --> 00:02:42.123
our sample size times one
minus P well one minus 15

00:02:42.123 --> 00:02:45.817
hundredths is going to be
85 hundredths and this is

00:02:45.817 --> 00:02:48.705
definitely going to be
greater than or equal to ten.

00:02:48.705 --> 00:02:51.628
Let's see this is going to
be 24 less than 160 so this

00:02:51.628 --> 00:02:56.425
is going to be 136 which is
way larger than ten so that

00:02:56.425 --> 00:02:59.750
checks out and so the sampling
distribution of our sample

00:02:59.750 --> 00:03:03.987
proportions is approximately
going to be normal.

00:03:03.987 --> 00:03:06.376
And so what is the mean and
standard deviation of our

00:03:06.376 --> 00:03:08.349
sampling distribution?

00:03:08.349 --> 00:03:12.481
So the mean of our sampling
distribution is just going to

00:03:12.481 --> 00:03:15.562
be our population proportion,
we've seen that in other

00:03:15.562 --> 00:03:18.145
videos, which is equal to 0.15.

00:03:19.856 --> 00:03:23.777
And our standard deviation
of our sampling distribution

00:03:23.777 --> 00:03:27.944
of our sample proportions is
going to be equal to the square

00:03:28.821 --> 00:03:32.988
root of P times one minus
P over N which is equal to

00:03:35.040 --> 00:03:39.207
the square root of 0.15
times 0.85 all of that over

00:03:43.276 --> 00:03:47.311
our sample size 160, so now
let's get our calculator out.

00:03:47.311 --> 00:03:51.478
So I'm going to take the
square root of .15 times .85

00:04:00.227 --> 00:04:03.977
divided by 160 and we
close those parentheses

00:04:06.449 --> 00:04:09.053
and so what is this going to give me?

00:04:09.053 --> 00:04:13.184
So it's going to give me
approximately 0.028 and I'll

00:04:13.184 --> 00:04:15.365
go to the thousandths place here.

00:04:15.365 --> 00:04:17.948
So this is approximately 0.028.

00:04:19.776 --> 00:04:23.295
This is going to be approximately
a normal distribution

00:04:23.295 --> 00:04:26.898
so you could draw your classic
bell curve for a normal

00:04:26.898 --> 00:04:30.287
distribution, so something like this.

00:04:30.287 --> 00:04:34.454
And our normal distribution
is going to have a mean,

00:04:36.858 --> 00:04:40.479
it's going to have a mean
right over here of, so this

00:04:40.479 --> 00:04:44.348
is the mean, of our sampling
distribution, so this is

00:04:44.348 --> 00:04:48.047
going to be equal to the
same thing as our population

00:04:48.047 --> 00:04:51.755
proportion 0.15 and we
also know that our standard

00:04:51.755 --> 00:04:55.922
deviation here is going to
be approximately equal to

00:04:57.572 --> 00:05:02.227
0.028 and what we want to know
is what is the approximate

00:05:02.227 --> 00:05:05.892
probability that more than
10% of the sample would

00:05:05.892 --> 00:05:08.531
report that they experienced
extreme levels of stress

00:05:08.531 --> 00:05:11.060
during the past month,
so we could say that 10%

00:05:11.060 --> 00:05:14.951
would be right over here,
I'll say 0.10 and so

00:05:14.951 --> 00:05:18.760
the probability that in
a sample of 160 you get

00:05:18.760 --> 00:05:22.053
a proportion for that sample,
a sample proportion that

00:05:22.053 --> 00:05:26.220
is larger than 10% would be
this area right over here.

00:05:27.107 --> 00:05:31.107
So this right over here
would be the probability

00:05:32.004 --> 00:05:36.883
that your sample proportion
is greater than, they say

00:05:36.883 --> 00:05:41.050
is more than 10%, is more
than 0.10 just like that.

00:05:42.843 --> 00:05:47.292
And then to calculate it, I can
get out our calculator again

00:05:47.292 --> 00:05:51.458
so here I'm going to go to
my distribution menu right

00:05:51.458 --> 00:05:54.164
over there and then I'm going
to do a normal cumulative

00:05:54.164 --> 00:05:58.530
distribution function, so
let me click Enter there.

00:05:58.530 --> 00:06:00.468
And so what is my lower bound?

00:06:00.468 --> 00:06:04.635
Well my lower bound is 10%
0.1, what is my upper bound?

00:06:06.132 --> 00:06:09.415
Well we'll just make this one
'cause that is the highest

00:06:09.415 --> 00:06:14.260
proportion you could have
for a sampling distribution

00:06:14.260 --> 00:06:16.788
of sample proportions.

00:06:16.788 --> 00:06:20.955
Now what is our mean well
we already know that's 0.15.

00:06:22.124 --> 00:06:25.066
What is the standard deviation
of our sampling distribution?

00:06:25.066 --> 00:06:29.233
Well it's approximately 0.028
and then I can click Enter

00:06:33.054 --> 00:06:35.934
and if you're taking an AP
exam you actually should write

00:06:35.934 --> 00:06:38.788
this you should say, you
should tell the graders

00:06:38.788 --> 00:06:41.323
what you're actually typing
in in your normal CDF

00:06:41.323 --> 00:06:44.814
function, but if we click
Enter right over here,

00:06:44.814 --> 00:06:48.981
and then Enter, there we have
it, it's approximately 96%.

00:06:50.223 --> 00:06:54.390
So this is approximately 0.96
and then out of our choices

00:06:55.406 --> 00:06:57.597
it would be this one right over here.

00:06:57.597 --> 00:06:59.887
If you were taking this on
the AP exam you would say that

00:06:59.887 --> 00:07:04.054
called, called normal normal
CDF where you have your

00:07:09.315 --> 00:07:13.482
lower bound, lower bound, and
you would put in your 0.10

00:07:16.181 --> 00:07:20.651
you would say they use an
upper bound, upper bound

00:07:20.651 --> 00:07:25.028
of one, you would say that
you gave a mean of 0.15

00:07:25.028 --> 00:07:29.831
and then you gave a
standard deviation of 0.028,

00:07:29.831 --> 00:07:32.342
just so people know that you
knew what you were doing.

00:07:32.342 --> 00:07:34.202
But hopefully this is helpful.