[Instructor] Hi, we're back for part two
of our bioenergetics lecture.
We left off talking about how energy is produced
by different reactions.
And this slide is depicting some exergonic reactions
and endergonic reactions.
So if you recall, exergonic reactions produce energy,
and endergonic reactions require energy
to make them occur to produce more energy.
So the blue gears are exergonic reactions,
so they're gonna be producing energy
to make these green reactions occur.
And these green reactions are going to produce more energy.
So in this case, we're eating some food, some carbohydrates,
and that's producing ATP,
which is going to then
cause these other endergonic reactions to start.
So the energy pathways that our body is capable
of utilizing are aerobic, with oxygen,
and anaerobic, without oxygen.
So aerobic pathways are capable
of generating large amounts of ATP,
but it generates it slowly.
And this aerobic respiration occurs
within the mitochondria of our cells.
And we can utilize all three macronutrients,
carbs, proteins, and fats,
as a fuel source for aerobic energy pathways.
Anaerobic energy pathways generates smaller,
limited quantities of ATP.
However, the ATP is created really quickly,
so this is if you need a sudden burst of energy.
You're gonna use stores that are already made in your body.
And you can only utilize carbohydrates
as the fuel source for this anaerobic activity.
This anaerobic respiration takes place
within the cell sarcoplasm.
The production of ATP occurs
via three different metabolic pathways,
and these pathways are activated
at the beginning of muscle contraction.
So as we start moving and using our muscles,
our muscles require ATP to function.
The first pathway is the phosphocreatine ATP pathway.
So ATP is formed by breaking down phosphocreatine.
The second pathway to form ATP
is via the glycolytic pathway, glycolysis.
And this is via the degradation of glucose,
which is found in our blood,
or glycogen, which is found in our muscles.
And then the last metabolic pathway
is the oxidative pathway to form ATP.
ATP formed via the phosphocreatine pathway
and glycolysis does not involve the use of oxygen.
So these two pathways are anaerobic.
ATP formed by oxidative processes
is an aerobic metabolism and uses oxygen.
And so this little diagram shows three different pathways,
so the anaerobic pathway, the phosphagen system,
and the glycolytic system.
These are without oxygen, so they're fast-acting.
And then the aerobic pathway,
the oxidative pathway, is with oxygen.
So the phosphagen system, the ATP-PC system,
provides energy for muscle contraction
at the start of exercise
and during short, high-intensity activity.
So when you're sprinting
or running quickly across the street,
it's something that is a very fast movement
that doesn't last a long time.
And this reaction is a really simple one-enzyme reaction.
The phosphagen system is the quickest way
for our body to generate ATP.
This phosphagen system takes creatine phosphate,
which is stored in our skeletal muscles,
and it donates a phosphate to ADP to produce ATP.
So the pathway has two components.
There's molecules of ATP.
So you can see here, here's our creatine phosphate,
and an enzyme, creatine kinase, splits the molecule
into two components, creatine and phosphate.
And then the ATP bond is broken,
so breaking ATP into ADP.
And the creatine phosphate
adds a phosphate to the ADP to make ATP.
And this reaction is for short-term,
high-intensity exercise.
And this is for activities
that are lasting less than five seconds
because we quickly deplete any of the creatine phosphate
and the stored ATP in our system to produce it.
The second pathway is glycolysis,
and this is also an anaerobic, without oxygen, process.
Glycolysis consists of the breakdown
of glucose, which is in the blood,
or muscle glycogen, to form two molecules of pyruvate acid
or lactic acid if no O2 is present.
So I'll show you this on another slide,
so hopefully it'll make sense.
There's a series
of enzymatically catalyzed coupled reactions,
so the whole series of steps which occur
in the sarcoplasm of the muscle cells.
And glycolysis produces a net gain of two molecules of ATP
and two molecules of pyruvic
or lactic acid per glucose molecule.
The energy-investment phase
to kind of get the system going requires two ATPs to start.
The energy-generation phase produces actually four ATP,
but because you use two at the start, it's a net of two ATP.
So to summarize the energy investment phase of glycolysis,
which is part one, there's five different reactions,
and these five reactions are gonna require the utilization
of ATP to continue to proceed through them.
So what I'd like you to understand is
that in the energy-investment phase of glycolysis,
two ATP are used.
During this energy investment phase,
as I said earlier, two ATP are used,
and then that can allow the glycolysis pathway
to continue into the energy generation phase.
This phase requires hydrogen molecules,
and so these hydrogen molecules need to be transported.
And they're transported via NAD and FAD.
So the NAD is gonna accept one hydrogen,
and it's gonna convert it into NADH.
So there needs to be adequate amounts
of NAD within the system
to be able to accept the hydrogen atoms
to continue the process.
So this schematic depicts the whole process of glycolysis,
the energy-investment phase requiring two ATP
and the energy-generation phase,
which is producing four ATP.
The energy-investment phase needs two ATP to get it going.
The one ATP is needed to get the glucose
from the blood into the cell
to start having the cell be able to utilize that glucose.
The energy generation phase is producing four ATP.
However, because we use two at the beginning,
the net that glycolysis produces is two ATP.
Because NAD accepted the hydrogen atom,
there were two NAD in this process.
And so there are two NADH produced.
The NADH will go on
to become pyruvate or lactate molecules.
So the net production for glycolysis,
what you need to know is
if there is one glucose molecule to start the process,
the output is going to be two pyruvate
or two lactate molecules, two ATP, and two NADH.
If oxygen is available within the system,
so if it's an aerobic system,
the hydrogens from the NADH can be shuttled
into the mitochondria of the cell,
which will get into the aerobic production of ATP.
If oxygen is not available,
so if it's an aerobic process,
the hydrogens can't be accepted in the mitochondria.
So pyruvic acid will take that hydrogen
and form lactic acid.
Here is a very busy picture
of the whole process of glycolysis.
And on the left-hand side of the screen
are the written words to describe the process.
And on the right-hand side is just a diagram.
So you can see here glucose
up at the tippy-top is in the blood,
and that is being used to go into the cell.
So one ATP is used to get that glucose into the cell.
And then we have our series of cellular changes
and reactions of changing glucose 6-phosphate
to fructose 6-phosphate.
Another ATP is used to produce fructose 1,6 biphosphate.
And in this case,
we now proceed through the energy-investment phase
to the energy-generation phase.
The energy-investment phase
is a series of five steps,
and the net result of the series
of the first investment phase, five steps, is the production
of two glyceraldehyde 3-phosphate molecules.
So one glucose molecule
will produce two glyceraldehyde 3-phosphates.
And this begins the second part of glycolysis, phase two,
which is the energy-generation phase.
This series of reactions
are a total of five additional reactions.
And the net result
of this second phase of glycolysis
is the production of two ATPs
per glyceraldehyde 3-phosphates
and two pyruvate molecules.
This is where the NADH becomes important
or NED becomes important
because for this second phase of glycolysis to proceed,
NAD needs to accept a hydrogen.
Otherwise the whole process stops here
at the end of the investment phase.
So NAD needs to be present to accept that hydrogen
for this series of the remaining five
enzymatically generated reactions to proceed.
So NAD is gonna accept one hydrogen,
and it's gonna convert to NADH.
The ATP is going to be produced along the way,
and then pyruvate will be formed.
If oxygen is available,
these hydrogens from the NADH can be shuttled
to the mitochondria of the cell
to contribute to aerobic production of ATP.
If oxygen is not available,
if it's an anaerobic activity,
the hydrogens cannot be accepted
or moved into the mitochondria.
So the pyruvic acid, pyruvate,
will transform to pyruvic acid,
and if there is lactate dehydrogenase present, an enzyme,
this can convert the pyruvic acid to lactic acid.
And this conversion to lactic acid
generates an NAD, which now can go back up
to the top of the beginning of phase-two glycolysis
to allow glycolysis to continue.
To summarize, the energy investment phase is a series
of five reactions using two ATP
and producing two glyceraldehyde 3-phosphates.
The phase two of glycolysis, the energy-generation phase,
proceeds through, if NAD is present, to accept a hydrogen.
And then those next remaining steps, six to 10,
it's like a 10-step process for glycolysis.
So step six to 10 are the energy-generation phase.
Two ATP will be produced.
Pyruvate will be produced.
If oxygen is not present, lactic acid will be produced.
If oxygen is present,
the hydrogen from the NADH will go to the mitochondria.
Both of those processes at the end
will allow glycolysis to continue.
So when NAD takes the hydrogen and becomes NADH,
we need at the end of the glycolytic process,
we need to get rid of that hydrogen, and there's two ways.
So if oxygen's present or if oxygen is not present,
either way, a hydrogen will be given up,
producing NAD to allow the cycle to continue.
After the 10-step glycolysis process,
two pyruvate molecules are formed.
So one glucose molecule will produce two pyruvates.
One glucose molecule will also produce two NADH.
So the end product of glycolysis is this production
of the two pyruvate molecules.
These pyruvates in the presence of oxygen will move
into the mitochondria, where they undergo further oxidation.
So you could see here is the pyruvate sitting out
in the cytoplasm.
With oxygen, it can move into the mitochondria,
where it reacts and transforms into acetyl-CoA.
This acetyl-CoA then moves
into another process called the Krebs cycle,
or it's also known as the citric acid cycle.
So here is the citric acid cycle,
and there's a series of processes
that occur within this cycle.
So one turn of this cycle one time around
will produce three NADH.
So here's a production of NAD accepting a hydrogen.
So there's an NADH.
Here's another NAD accepting a hydrogen, another NADH.
And here's another NAD accepting a hydrogen for a third NADH
It also produces one FADH over here.
FAD, if you recall, can also accept hydrogen.
Another important phosphate
is this guanosine triphosphate here.
Guanosine diphosphate can also accept a phosphate
to form GTP, and we'll talk a little bit about that later.
But GTP can also be used to produce ATP.
Aerobic ATP production occurs inside the mitochondria.
So if you recall, that pyruvate moves into the mitochondria.
Two cooperative metabolic pathways occur.
One is the Krebs cycle,
which we discussed on the prior slide.
The Krebs cycle will generate two acetyl-CoAs
and will be oxidized in the Krebs cycle.
The other metabolic pathway
is the electronic transport chain,
and this chain is the process of oxidative phosphorylation,
which is the process of ATP formation.
The Krebs cycle,
it's more commonly now called the citric acid cycle.
And this citric acid cycle completes the oxidation,
or the removal of hydrogen,
of carbohydrates, fats, and proteins,
so our food macronutrients,
using NAD and FAD as the hydrogen carriers.
So recall we need to mobilize hydrogen molecules,
and NAD and FAD are the molecules
that can accept these hydrogens.
The hydrogens contain the potential energy
in the food molecules.
So the hydrogens are really, really important
as are the structures that are needed to carry the hydrogens
to make these cycles continue.
The potential energy of hydrogen can be used
in the electron transport chain
to combine ADP plus phosphate to reform into ATP.
And this process of aerobic production
of ATP is oxidative phosphorylation.
Here's another schematic of the citric acid cycle.
So important things to know,
again, just to summarize this,
pyruvate enters into the mitochondria and forms acetyl-CoA.
Acetyl-CoA then
is formed into citrate,
and this is why this cycle is called the citric acid cycle,
because that's the main structure
that starts this Krebs cycle.
The oxidation of pyruvate from glycolysis
starts this whole enzymatically catalyzed cycle.
Hydrogens are bound to NAD and FAD and GDP.
One full turn of this Krebs cycle will produce three NADH,
and I showed you in the other slide.
So here's an NADH.
Here's another NADH.
Here's another, and an FADH.
So you get three NADH and one FADH.
At the end of the cycle, oxaloacetate is formed.
This is a substrate that binds with the acetyl-CoA,
and this binding of oxaloacetate
to acetyl-CoA is what forms the citrate.
To go back to the beginning
where we had glucose in the blood entering into the cell,
each molecule of glucose results
in two turns of the Krebs cycle.
Why is that?
So think for a moment.
It's two turns of the Krebs cycle
because at the end of glycolysis, two pyruvate are formed.
So two pyruvate will enter into the mitochondria,
and each of those pyruvates
will start up a citric acid cycle.
The primary function of the citric acid cycle
is to remove hydrogens
and the energy associated with those hydrogens.
NAD and FAD pick up the hydrogens
and convert to NADH and FADH.
For each turn of these two Krebs cycles,
three molecules of NADH
and one molecule of FADH are formed.
So there's a net then of six NADH
and two FADH per glucose.
For each NADH, enough energy is available
to produce 2 1/2 ATPs.
For each FADH, enough energy is available
to produce 1 1/2 ATPs.
I've put this little table here.
For two turns of the Krebs cycle, which occurs
because one glucose molecule produces two pyruvates,
which are going to enter the mitochondria
and cause two turns of the Krebs cycle,
and with two turns of the Krebs cycle,
we're gonna have six NADH and two FADH,
yielding 18 ATP molecules
for the citric acid cycle.
Now the guanosine triphosphate,
which I talked about earlier,
is another high-energy compound formed
through the Krebs cycle process.
This GTP can transfer its phosphate group to ADP
to form another ATP.
So GTP contributes one ATP
per turn of the Krebs cycle.
As we know, there are two turns to the Krebs cycle
for every molecule of glucose.
So GTP will produce a net of two ATP.
Therefore for two turns of the Krebs cycle,
we are going to produce 20 ATPs.
After the citric acid cycle has completed its two turns,
we have those three NADH and one FADH,
and these are taken to the electron transport chain
to re-phosphorylate ADP to ATP to make more energy.
So electrons are removed from hydrogen atoms
and are passed down a series of electron carriers,
or cytochromes.
During the passage of these electrons
down the cytochrome chain,
energy is released to re-phosphorylate ADP to ATP
at three different sites.
Here's an image of the electron transport chain.
Oxidation of compounds in the electron transport chain
coupled with the phosphorylation of ATP is referred to
as oxidative phosphorylation.
The FADH and NADH molecules produced from glycolysis
and the Krebs cycle donate protons
and electrons to the electron transport chain.
And at specific steps along the chain,
sufficient free energy is released
to phosphorylate ATP molecules from ADP and phosphate.
You can see over here,
here's our NADH releasing its hydrogen.
Here's our FADH releasing its hydrogen.
Here's our hydrogen coming back in to combine
and work to produce ATP
from the ADP and phosphate.
To summarize how many ATPs are produced
during glycolysis and the Krebs cycle,
we need to look at each of these cycles individually
and remember that in glycolysis, two NADH were formed,
and for each NADH, 2 1/2 ATPs are produced.
So if there's two NADHs, there's gonna be five ATPs.
What we also need to remember,
and we didn't talk about this yet,
the process of glycolysis depends
on whether the body's using glucose or glycogen.
And if it's using glucose,
which is the process we have talked about so far,
the energy-investment phase requires two ATPs.
So the net is two ATPs are produced.
So the energy investment phase is two ATPs.
One ATP is used to get that glucose
from the blood into the cell.
And then in the energy-generation phase,
four ATP are produced.
So four produced minus two used is a net of two.
If the body's using glycogen,
which is already within the muscle cell,
you don't need to use an ATP
to transport that sugar substrate into the muscle.
It's already in there.
So we don't need to use that one ATP.
So only one ATP is used
in the energy-generation phase if we're utilizing glycogen.
And then four ATP are produced
in the energy-generation phase.
So four minus one is three ATP.
So just thinking about that
and understanding the difference of the glucose
versus the glycogen.
Two NADH are formed during the conversion
of pyruvate to acetyl-CoA.
And so there's four, five more ATP
during our citric acid cycle.
For each turn of the citric acid cycle,
there are three NADH,
and you recall that there are two turns
per glucose molecule.
So the net result of our citric acid cycle
are six NADH, two FADH, and two GTPs.
So we're gonna get 15 ATP from the NADH,
three ATP from FADH, and two ATP from the GTP.
The overall total ATP from carbohydrates then,
starting with glucose in the muscle
and brain cells, yields 36 ATP.
Starting with glycogen in the muscle, yields 37 ATP
because we didn't use one ATP
at the beginning of the glycolysis phase.
If we are starting with glucose in the liver, kidney,
and cardiac cells, we're gonna get 38 ATP.
If we are starting with glycogen in the liver, kidney,
and cardiac cells, we're gonna yield 39 ATP.
However, the net result for glucose is really 32,
and glycogen, 33, due to different ATP uses.
This image here gives a nice overview
of all of the different systems that are used
to metabolize fats, carbs, or proteins.
So far, we have been talking just about glucose
and glycogen, carbohydrates, looking at glycolysis,
and then the citric acid cycle
and then the electron transport chain.
Aerobic respiration or mitochondrial respiration,
the production of ATP molecules
in this pathway using fats is the greatest,
but it's way slower than either the phosphagen system
or the glycolytic system.
Remember that all three of these macronutrients, though,
serve as fuel substrate for the manufacturer of energy.
Fat oxidation, lipid oxidation, is an important source
of free energy for ATP production.
And the primary source of lipids are free fatty acids.
The activation of the sympathetic nervous system brought on
by stressors provides a signal to begin the breakdown
of stored triglycerides in our muscles
or in our adipose tissue.
Beta-oxidation, or the breakdown of our free fatty acids
into two carbon fragments,
involves usually three different stages.
The first is the activation
of the free fatty acids in the cytosol
and a series of enzymatic processes
and then the transport of the activated free fatty acids
into the mitochondria via a carnitine shuttle,
and then the beta oxidation in the mitochondrial matrix.
Each beta oxidation sequence removes a two-carbon segment
that results in the manufacturer of one acetyl-CoA.
And we already know what acetyl-CoA can do.
And it also simultaneously removes electrons and hydrogen,
reducing NAD and FAD to NADH and FADH.
Again, we know what they do.
They can all work to produce ATP.
So this is a schematic here with the activation
of the free fatty acids in phase one
and then the transport of the free fatty acids
via the mitochondrial shuttle
and beta-oxidation proper in this matrix,
producing acetyl-CoA.
And then acetyl-CoA will go into the Krebs cycle.
FADs and NADs will go into the electron transport chain,
and then we will have complete palmitate degradation,
which we're gonna talk about on the upcoming slides.
Palmitate is the most common free fatty acid utilized
by our body to produce energy.
However, there are others, and they vary in length,
and the net ATP yield will vary from structure to structure.
But we're gonna focus on palmitate
because it is the most common.
And to oxidize these lipids into energy,
as I said on the other states' slide,
there's three different steps,
and the first is that the free fatty acids,
they need to be activated.
And they need to be shuttled into the mitochondria,
which requires energy 'cause free fatty acids
can't penetrate the biologic membranes.
So they have to cross the membrane
with a specific process which requires two ATPs.
Once the fatty acid is inside the mitochondrial matrix,
beta-oxidation occurs by cleaving two carbons every cycle
to form acetyl-CoA.
So palmitate is a 16-carbon structure.
So two carbons
every cycle will yield eight cycles,
and this will result in the production of eight acetyl-CoA.
This cleaving of the two-carbon fragments
from the 16-carbon structure occurs seven different times.
So the beta-oxidation sequence must occur seven times
to yield eight two-carbon fragments.
During this seven beta-oxidation sequences,
seven NADH are formed, and seven FADH are formed.
You can see the total number of ATP formed
from one palmitate free fatty acid.
So there's a lot of ATP formed when we use fats
as our nutrient for energy.
Our final macronutrient to talk about is protein.
Proteins are a substrate that can be catabolized.
They do provide the free energy required
to manufacture ATP during exercise.
A major point of entry for amino acid skeletons
into the energy pathways, specifically the Krebs cycle,
is acetyl-CoA.
And the maximal contribution of amino acid oxidation
to total ATP production during exercise
is somewhere between five and 10%.
So it's not like the carbs or the fats.
Our exercise science textbook refers to these processes
of metabolizing these nutrients into energy
as the metabolic mill.
And they have a nice video
that I've put on Blackboard that you can see.
It's pretty short, and it's visual,
so it will help cement the ideas in.
So definitely look at the video
and use the textbook as a reference
'cause I've skimmed over many of the the details here.
I'm just trying to capture the important components for you,
the take-home messages.
And just understanding that all three fuels,
carbohydrates, proteins, and fats,
serve integrated roles in contributing
to the production of energy.
Pyruvate is transported into the mitochondria
for conversion to acetyl-CoA
or converted to lactate in the sarcoplasm.
And if you recall, pyruvate is produced
via glycolysis using either glucose or glycogen.
Triglycerides or fats separate
into free fatty acids before entering the mitochondria,
where they're shuttled in via that carnitine shuttle
where they undergo beta-oxidation
for the conversion to acetyl-CoA.
Since free fatty acids enter the metabolic pathway
at this point, they cannot be converted to glucose.
Glycerol is a three-carbon structure,
and it's capable of entering the glycolytic pathway
or can be converted to either glucose or pyruvate.
And we saw this in the glycolysis pathway.
Glucogenic amino acids are those
that enter the pathway before the formation of pyruvate
and can be converted to glucose.
And ketogenic amino acids enter the pathway as acetyl-CoA
or as a citric-acid-cycle intermediate product.
And so they can only be used to produce energy.
Looking at the role of energy pathway in exercise fatigue.
When we're working out,
muscle contraction depends on the ability
of the metabolic pathways to contribute
to the production of ATP.
Mitochondrial respiration is a primary supplier
of ATP using fat, carbohydrates,
and proteins made available for mitochondrial aspiration,
so the beta-oxidation cycle.
The availability of muscle glycogen limits glycolysis
and maintenance of maximal rate of ATP production.
Research has reported
that muscle glycogen stores become depleted
after approximately two hours of exercise
under high-intensity exercise or maximal usage.
The relative contribution of each energy system is dictated
by the required energy demands.
So there's not really a fine line of when one starts
and the other stops.
There's a definite contribution in overlap.
Each system contributes from the beginning
of an exercise balance to steady state exercise.
And steady state is often referred to
as when you get your second wind during exercise.
So if you're running, and you start running,
and the first couple minutes you feel like you're gonna die,
and you can't catch your breath,
but then all of a sudden,
you kind of shift into a different gear.
And that's when you get in your second wind,
and you're in the steady state.
This says generally takes between 45 to 90 seconds
or up to four hours to achieve.
These are some nice slides
showing the different energy systems in the overlap.
Looking here at the very start of exercise,
100% of the energy is
through the creatine phosphate hydrolysis.
But that drops off really, really quickly.
And then we will go into our glycolysis
for the first minute up to four minutes
and where our mitochondrial respiration is also starting.
So they're all overlapping.
But as glycolysis drops off,
and we're depleting those glycogen stores,
we're going into that mitochondrial respiration
and hitting our steady state.
Another table looking at the different energy systems.
For a quick burst of energy, maximal effort,
zero to five seconds,
we're primarily utilizing the phosphagen system.
Six to 30 seconds of very intense exercise,
again, we're using that phosphagen system,
which becomes depleted after about 10 seconds.
From 30 to 120 seconds of intense exercise,
we're using our fast glycolytic system.
Two to three minutes with moderate activity,
our fast glycolytic, but that becomes depleted.
And then we're crossing over into our aerobic system.
And greater than three minutes,
we're using our oxidative system almost exclusively.
The differences in our energy systems,
there are some gender or actually sex differences.
Men have a greater proportion of type-two muscle fibers,
which means they have a greater potential
for the phosphagen system.
They have greater creatine kinase activity,
and this accompanies increased creatine phosphate levels.
So the interpretation is that the ATP contribution
from the phosphagen system
will support greater anaerobic performance in men.
The key enzymes involved in glycolysis,
including phosphorylase and phosphofructokinase, or PFK,
have also been found in higher concentrations in men.
And there's no difference
that has been reported between genders
in the key enzymes involved in mitochondrial respiration,
the Krebs cycle and electronic transport chain
and beta-oxidation.
It's difficult to separate changes
in physiologic function that occur from age alone
versus the effects of aging combined
with physical inactivity.
So this is a issue here.
Many older adults lose muscle mass, lose VO2 capacity,
not solely from the effects of aging,
but more from the effects of being sedentary.
So in many of the studies,
if you just take a population
of older adults that are heterogeneous,
you can't really sift out the changes.
A better study is to look at active older adults to do that.
So at this point, it's hard to separate out the changes.
Aging does contribute to an overall decline
in skeletal muscle fibers.
We do get sarcopenia as we age.
Differences in the energy systems,
the capacity of energy pathways and the effects of training,
so looking at training.
For short-term high-intensity training,
there's a significant increase in resting concentrations
of creatine phosphate stores in the skeletal muscle.
So even though I talked about those biologic sex differences
in men or the male sex
having more creatine phosphate stores,
with training, you can increase those stores.
Creating kinase, which is the enzyme
that stimulates the phosphagen system,
also is up-regulated with training.
With training, there's increased glucose delivery
to the working muscles.
There's increased resting concentrations of muscle glycogen,
so it's there ready for you to start working.
There's an elevation
of the primary rate-limiting enzymes of glycolysis,
so the phosphorylase and phosphofructokinase.
So those enzymes are there ready to get things going.
There's an enhanced capacity
for tolerating proton accumulation and clearance,
so we can better tolerate
when that lactate is in our system.
We also have an increased activity
of the enzyme lactate dehydrogenase,
the enzyme that permits rapid conversion
of the pyruvate to lactate.
Two, if you recall, cleave that hydrogen off of the NADH
to allow that glycolysis to continue.
With prolonged sub-max endurance training,
this is primarily reliant on our mitochondrial respiration.
We will see an increase
in our mitochondria mass and numbers,
which will allow us to become more efficient
and utilize more oxygen.
This will also increase,
We see increases in glucose and free fatty acid delivery
and resting concentrations of muscle glycogen.
We have increases in the muscle glycogen content,
which is what I said in the other line above.
There's a greater capacity for pyruvate uptake
and oxidation through mitochondrial respiration,
resulting in increased ATP production
and the potential to sustain higher intensities
of steady state exercise.
We become conditioned to be able to work longer
at a higher rate.
There are really good multiple adaptations
to our cardiovascular system.
There's expanded blood volume.
There's expanded left ventricular chamber size,
capillary density, and our pulmonary system.
There's more conditioned respiratory muscles.
We have a bigger air volume,
and so these cellular adaptions
help improve our overall metabolic efficiency.
This is gonna be our activity for labs,
so I am not going to talk about this right now.
And I think this is complete.