Hi welcome to the next episode of Cell-fie
Science I'm Jen and I'm bringing you a quick
burst of science from my cell phone today
we're going to be talking about photosynthesis
which is why i have this bright light behind
me photosynthesis is the process by which
plants take light from the sunlight and change
it into biological energy but did you know
that it actually requires two separate chemical
reactions that's right what we think of as
photosynthesis light into sugar takes two
different reactions the first is called the
light-dependent reaction in this reaction
sunlight is captured and turned into chemical
energy in the form of ATP and NADPH with oxygen
as the biproduct which if you remember from
our stomata video is what plant's breath out
and on the other side is the light-independent
reactions sometimes called the Calvin cycle
in which the chemical energy from the light-dependent
reactions is used to fix carbon dioxide into
sugar Now plants have special organelles called
chloroplast where they perform photosynthesis
I isolated a whole bunch of chloroplasts in
this cuvette which is why it looks so green
because they're two separate reactions you
can actually measure photosynthesis with either
one today we're going to be doing the Hill
reaction which is named after the man who
discovered that photosynthesis was indeed
two separate reactions by taking a Hill reagent
which is anything that can accept an electron
at the end of the light-dependent reactions
we can observe the amount of photosynthesis
occurring today we're going to be using DCPIP
which has a blue coloration before it accepts
any electrons this is also sometimes marketed
as Vitamin C reagent so you can buy that on
Amazon or any other area when the DCPIP accepts
the electron or becomes reduced it will turn
colorless so we can actually measure these
colors today we're going to be adding some
chloroplasts to our DCPIP and I've isolated
a whole bunch of chloroplasts to do this so
here we go take some chloroplasts out add
it to our Hill reagent now it's very important
that you get this all mixed up because if
you have a blue layer and a green layer then
you're not getting the actual reaction now
I want you to observe the color versus the
color of pure chloroplasts we would expect
as the Hill reaction occurs this would start
turning this color so it will get lighter
in color you can also add stuff like herbicides
which is what I've done to this cuvette and
then measure the amount of color change by
using a spectrophotometer or you can do the
eyeball test and sometimes the eyeball test
is a lot easier so I have some that I prepared
earlier because this process takes time and
this is a short burst of science these guys
have been sitting under this really bright
light for about 20 minutes one had herbicide
and one did not based on what I showed you
before hang on sorry there we go based on
what I showed you before which one do you
think had the herbicide?
Did you guess the darker one?
You're right this is the one that only had
DCPIP and this one had DCPIP plus the herbicide
Diuron this herbicide decouples the light
dependent reaction that means the electrons
can no longer get from point A to point B
and give them to the DCPIP so no reaction
occurs in this one now you can do this with
all sorts of different stuff for example maybe
you want to look a different light intensities
put it closer to the light source or do you
have different colored LEDs what would happen
if you used blue or red or green you could
also use different compounds than Diuron but
remember if you're using any chemicals be
sure to follow their manufacturer instructions
additionally always wear your personal protective
gear gloves and glasses are a must and if
you're a kid be sure you have parental approval
I'll leave the recipes in the video description
so that you can make up the various solutions
to do this if you'd like to on your own but
for now that's light's out for this episode
of Cell-fie Science bye
