my gosh my neighbor is leaf blowing and
it's so loud and annoying hello
welcome I'm Miles and this is the field
so today we're diving in to the cold
hard science of photosynthesis down to
the very molecular level so when we talk
about photosynthesis there are two steps
that we need to talk about the first
step is the light dependent reactions
and following that is the light
independent reactions but we'll talk
first about the light dependent
reactions first light is absorbed into
photosystem 2 or PS2 for short which
excites an electron and gets it all
energized this electron zooms down an
electron transport chain to photosystem
2 which in which it gets reenergized
again this electron goes towards both
synthesizing ATP and turning NADP+
into NADPH so this may seem a little bit
confusing because if photosynthesis can
just make ATP and it's first step why
does it need the rest of photosynthesis
and the answer is storage so that's why
you turn it into glucose so then plants can
take out of their glucose reserves on
you know during the night time on
cloudy days stuff like that okay now
we're moving on to the light independent
reactions which take place inside of
what we call the Calvin cycle a
multi-step process which uses the ATP
and NADPH from the light dependent
reactions to eventually make glucose it
is basically three steps first step
carbon fixation
step 2 reduction step 3 regeneration or
if you prefer grab split leave switch
the cycle starts over again so the
first step is carbon fixation it starts
out with a molecule called ribulose
biphosphate otherwise known as RuBP it's
a five carbon chain with two phosphate
groups
so this rubp starts out by taking some
carbon dioxide from the atmosphere
making a six carbon molecule but this
six carbon molecule is very highly
unstable so it pretty much
instantaneously decays into two 3-carbon
molecules called 3-phosphoglyceric acid
or 3-PGA so we have two 3-PGA
molecules and for one whole cycle of the
carbon Calvin cycle we're going to need
three of those are RuBP molecules so
imagine that two more RuBP molecules just did 
the exact same thing so now we have six
molecules of 3-PGA ok so next up is
reduction
got stung by a stinging nettle no in reduction
what happens is ATP and NADPH work
together to turn 3-PGA into
glyceraldehyde 3-phosphate
otherwise known as G3P which is the
ultimate product of the Calvin cycle
this G3P can be converted into glucose it
can be converted into starch for really
long-term storage and I can even be
converted into cellulose which is used
for plant cell walls it's pretty cool
stuff the final step in the calvin cycle
is regeneration regeneration is the step
where the cycle kind of comes back upon
itself so at this point we have six
molecules of G3P one molecule of G3P
gets kicked out and goes to make glucose and
the rest stay in and they go right back
to the beginning to start the cycle over
again so the five remaining G3P
molecules are turned back into three RuBP
molecules and the cycle starts over
again and that's the calvin cycle
boom that's it you're done
