>> Welcome to metabolisms and bioenergetics, part four.
And in this video lecture, we're going to look
at how carbohydrates and fats and oils ultimately end
up producing ATP in our body.
It's [inaudible] grand finale of everything
that we've learned so far this semester.
Let's get started.
Alrighty. So we don't have enough time to get to proteins,
so we'll just focus on fats and oils
and carbohydrates, all right.
So with fats and oils, we have our triglycerides.
And so, the first thing that's going to need to happen, right,
is we're going to use our lipase enzyme
and water and do hydrolysis.
And we talked a lot about what's going on there,
and I'm not going to review that right now.
You have the videos.
The important thing, though, to focus on here is
that we end up with fatty acids.
And these fatty acids always have an even number
of carbons, all right.
And so, this spiral is representing beta-oxidation,
right, because we use a spiral instead of a circle
because each time there's a turn of the beta-oxidation, right,
there is a two-carbon loss forming acetyl-CoA.
So here's our acetyl-CoA, right here.
Okay. So as this fatty acid goes
through the beta-oxidation cycle, each time it does a turn,
each turn of the beta-oxidation, right,
is going to produce one FADH2 and one NADH,
right, and one acetyl-CoA.
Whoops, CoA.
Okay, good now.
And then remember, on the last turn, right,
the last turn gives two acetyl-CoA.
Alrighty. And so, really, the emphasis here is thinking
about the fats and the oil are the carbohydrates
that ultimately how many acetyl-CoA are produced,
because we know, right, that the acetyl group
from the acetyl-CoA, right.
And the sulfur's there.
Sometimes there show it.
Sometimes they don't, right.
So there's our acetyl group.
So there's the two carbons that enter the citric acid cycle.
So the real emphasis on looking at the energy production
of our food is how many reduced coenzymes come out
and how many acetyl-CoA.
So the reduced coenzymes can go directly
to the electron transport chain.
The acetyl-CoA is converted into the reduced coenzymes
to enter the electron transport chain.
So now, let's look at carbohydrates,
and let's get everybody to acetyl-CoA, right.
So now, looking at this sugar, ideally,
it's easy to see that that's glucose.
You've memorized your sugars, and then the process
of one glucose going to two pyruvates, right.
Here's our buddy pyruvate, all right.
So what's that process called, okay?
So glucose, one glucose forming two pyruvates,
that is called glycolysis.
And remember that takes place in the cytoplasm
or cytosol of the cell.
And so no mitochondria are needed.
So during glycolysis, we learned that,
in addition to the two pyruvates, we get a net gain
of two ATP and two NADHs, right.
So here's some energy produced right away.
And then here is some more reduced coenzymes
that can go directly into the electron transport chain.
Now for the pyruvate to be converted into acetyl-CoA,
two additional NADH are produced in the aerobic environment.
The pyruvate can be converted into our buddy acetyl-CoA.
And then here are the two carbons of acetyl-CoA
that will enter the citric acid cycle.
All right.
So now, we've put together all the pieces
and we understand how our food is breaking down
and forms acetyl-CoA, which can enter the citric acid cycle,
which we've studied very carefully before.
So here, we get, right, our NADH.
We get a couple of those.
We get an FADH2 here and another NADH, right.
And then there's our GTP, which is easily converted to ATP.
So it's these reduced coenzymes, right,
that enter the citric acid cycle, or excuse me,
the electron transport chain, right, reduced coenzymes.
All right.
Those enter the electron transport chain.
Some oxygen is needed, and we get ATP.
And so, from our previous video,
we learned that for one acetyl-CoA,
we can generate 12 ATP, all right,
and one NADH can give us three ATP,
and one FADH2 can give us two ATP, all right.
So we have reduced coenzymes being produced directly
from beta-oxidation and glycolysis,
and then we have additional reduced coenzymes formed
when this acetyl-CoA enters the citric acid cycle.
So now, on the last page of our notes,
we're going to put this all together
and do a calculation of our ATP yields.
All right.
Let's start with glucose, all right.
So glucose has a very simple chemical formula, C6H12O6.
And when we studied glycolysis,
we learned that there is a net gain of two ATP.
And so, that's just two ATP straight across.
And that we also produced from each glucose, right,
so glucose goes to two pyruvates,
and that produces two acetyl-CoA, right.
And in this process of the glycolysis,
we get two NADHs here, right.
And so, from the previous page, right,
we know we times that by three.
So we get six.
And then we get another two NADHs
when the pyruvate becomes acetyl-CoA.
So then we times that by three; we get another six there.
And so, from one glucose, we would end
up with two acetyl-CoA, right.
And we have learned that from each acetyl-CoA, right,
that would be times 12.
We'd get 12 ATP from each.
So we get the two acetyl-CoAs times 12, and that's 24.
So when we add this all up,
we would get 38 ATP produced from one glucose.
Now don't get too attached to this number.
When you start looking through different textbooks
and different resources, they'll say anywhere from 32
to 38 are reported, and, typically,
36 is the most common answer.
And I think the reason for that is
because there are six carbons, right.
So if we have 36 ATP and we started with six carbons,
we could see that we get six ATP per carbon,
right, in the glucose.
All right.
So let's compare the energy production of glucose
to the energy production of one fatty acid, all right,
because we always talk about how fats, right,
there's more calories in fats than carbohydrates.
Now we're going to know why.
Alrighty. So here, let's look at myristic acid, all right.
So there's 12, 13, 14.
So this is a 14-carbon fatty acid.
Alrighty. So we need to think about what we've learned
about beta-oxidation, all right.
So how many turns are going to be needed, right?
We're going to need six turns of the beta-oxidation.
And from those six turns, right, acetyl-CoA, think of that
as a two-carbon, right.
So how many sets of two can we get from 14?
So we're going to get seven acetyl-CoA
because whenever we think about acetyl-CoA, we want to think
of it as this two-carbon handoff unit.
Alrighty. So from the beta-oxidation,
we have six turns.
That means we're going to get six FADH2s and six NADHs.
Those come from the turns of the beta-oxidation.
And then, we're going to get seven acetyl-CoAs
because these are two-carbon units
and we have 14 carbons altogether; however,
at the beginning, to initiate beta-oxidation, right,
activation of the beta-oxidation actually consumes,
let me use a different color here, consumes to ATP
because ATP goes to AMP, so we count that as a two, all right.
So that's why we have a minus here, minus two.
All right.
Yeah, okay.
I think that'll work.
All right.
Now, remember what we talked about with, right, FADHs.
They each produce two ATP.
So if we had six and each of those is going
to produce two ATP, altogether, that would be 12.
And then the NADH is, remember
that those would give us three ATP.
So 6 times 3 would be 18.
And then, right, the acetyl-CoAs,
those each produce 12, all right.
So 7 times 12 is 84.
So we add these all up, subtract two,
and we get 112 ATP, all right.
So we get a lot more energy, all right.
So this could be a little misleading though
because we started with a lot more carbons.
So yeah, fats, you know, we get more calories from fats
than we do carbohydrates,
but we need to normalize this for the carbons.
So we have 112 ATP, but initially,
right, we had 14 carbons.
So when we do the math here, it basically goes
to eight ATP per carbon, which is, right,
which is 33% more, right.
So that's 33% more ATP per carbon than glucose.
So back at the [inaudible] for exam one,
we were studying the calories from our food and we noticed
that there are more calories per grams of fat
than there are carbohydrates.
And here is the underlying biochemical reason why.
Alrighty. Well, this wraps up our video series
on metabolism and bioenergetics.
This would be a great time
to work your post-video practice problems.