Oxidative Phosphorylation and Chemiosmosis

Oxidative Phosphorylation and Chemiosmosis (along with slight correction of previous video)

I made a slight error
in the electron

transport chain video.

And I just wanted to correct
it in this one.

And it's also an opportunity for
me to include a little bit

of terminology that I forgot
to include in that video.

So when I described the electron
transport chain, you

remember, it's just you have
some high-energy electrons in

NADH and they get transferred
from one molecule to another.

And as they get transferred
they go into lower energy

states and they release
energy.

And then the final electron
acceptor was oxygen.

Oxygen got reduced right here.

But if you look at both sides of
this equation, the mistake

was, I need two hydrogens.

If I have two hydrogens on the
right-hand side of the water,

I need two hydrogens on
the left-hand side.

So there should be
a 2 right there.

So that was what I would
consider to be a minor mistake

in the last video.

But this also gives me a chance
to introduce you to

some more terminology.

So this whole process, we know
that this is called oxidation.

When NADH loses a hydrogen.

Remember oxidation is losing,
formally electrons.

But when it loses the hydrogen,
it loses the

opportunity to hog that
hydrogen's electrons.

So this whole process of the
electron transport chain is

one molecule after another
getting oxidized until you

have a final electron
acceptor in water.

So this is-- obviously you could
call this oxidation.

You know, just very generally.

And then the second part of the
electron transport chain--

or maybe we shouldn't even call
this part of the electron

transport chain-- the
process where the

ATP is actually formed.

The adding of a phosphate group
to another molecule is

called phosphorylation.

So the whole process of creating
ATP through the

electron transport chain.

Remember the electron transport
chain releases

energy that creates this
hydrogen gradient.

It pumps the hydrogens to
the outer compartment.

And then that gradient, those
hydrogens that want to get

back into the matrix,
essentially going back through

this ATP synthase.

This process of generating ATP
this way is called oxidative

phosphorylation.

It's a good word to know.

You might see it on some
standardized tests or on your

exams. And it's called
this because you have

an oxidative part.

Each of these molecules gets
oxidized in the electron

transport chain as they lose
their hydrogens or as they

lose their electrons.

That creates a hydrogen
gradient.

And then that, through
chemiosmosis, allows for

phosphorylation.

So that's another good
word to know.

The transfer of these hydrogens,
these kind of going

through this membrane
selectively.

This membrane, this ATP
synthase, wouldn't allow just

any molecule to go through it.

It's allowing these hydrogen
protons to go through it.

This process right here of this
hydrogen going through is

called chemiosmosis.

Another good word to know.

So the entire process
is called oxidative

phosphorylation.

They don't happen at
the same time.

Oxidative generates the energy
because the energy to push the

hydrogens out.

And then the phosphorylation
happens as the hydrogens

experience chemiosmosis and go
back in and turn this little

axle and then push the ADP and
the phosphate groups together.

And then you can contrast
that with substrate.

Substrate phosphorylations.

Since I'm in the mood to
introduce you to terminology.

Substrate phosphorylation.

This is actually what happens
when the ATP is produced

directly in glycolysis
in the Krebs cycle.

And this is where you have an
enzyme directly helping to

peruse the ATP without
any type of

chemiosmosis or proton gradient.

So if you imagine an
enzyme, some blurb,

some big protein blurb.

And let's say it has the
ADP there with its

two phosphate groups.

And then maybe it has another
phosphate group that attaches

at some other part of the
enzyme, this enzyme

facilitates without any kind of
chemiosmosis or oxidation.

It facilitates, probably in
conjunction with other energy

releasing reactions that may be
occurring on other parts of

the enzyme.

So maybe you can imagine a
little spark right there and

then that twists this
entire enzyme.

This isn't exactly how
it might work,

but it's a good idea.

And then these two things maybe
get pushed together.

When it's just an enzyme
without any of this

chemiosmosis that's driven by
oxidation, like we learned in

the electron transport chain,
we call this substrate

phosphorylation.

And the substrates are just the
things that attach to the

enzyme and have something
performed on them.

So anyway, hopefully you
found this little

video mildly useful.