Hi. It's Mr. Andersen and in this video I'm going to talk about anaerobic
cellular respiration. Or cellular respiration without oxygen. To understand anaerobic you
must first understand aerobic respiration. And so if these terms don't make sense to
you, glycolysis, Kreb Cycle and Electron Transport Chain, and if you don't even know what a mitochondria
is, you may want to go watch one of my videos on that. And I'll put a video link right up
here. But what is anaerobic cellular respiration? That's when we don't have oxygen. Or we don't
have a mitochondria present. And so let's get rid of those. And so what is anaerobic
respiration? It's really just glycolysis and then a new process called fermentation. And
so let's dig in a little bit deeper. So this is all the steps of cellular respiration.
Remember we begin with glucose. In glycolysis we break that down into pyruvate. How much
energy do we get from that? We get 2 ATP. Now we put in some ATP, but we net a total
of 2 ATP. What happens to the pyruvate? It's going to go into the mitochondria. It enters
into the Kreb Cycle after it's converted to acetyl COA. We give off all of that carbon
as carbon dioxide. And we make another 2 ATP. And so we haven't released that much energy
yet. Where did the energy go? It's stored in NADH and FADH2. They're going to transfer
their electrons through the electron transport chain. Eventually those electrons go to oxygen
with the formation of water. And we're going to make most of our ATP here. And so we're
going to make somewhere between 32 and 34 ATP. And so we net around 38, but there's
controversy. It's probably not as much as that. But how could we break this process?
Well we could break this process, number one if we didn't have any glucose. But we usually
have enough food inside our body. We could break this in two ways. We could get rid of
the mitochondria. So if there was a toxin that destroyed the mitochondria for example.
Or if we just didn't have enough mitochondria present. Or if we didn't have oxygen. Remember
oxygen is right here at the end. It's receiving those electrons. It's the final electron acceptor.
And if we don't have that, the whole thing kind of backs up. And so we're out of luck.
And we would be out of luck if it weren't for anaerobic respiration. If you want to
feel what anaerobic respiration feels like, just hold your breath for awhile. You're going
to run out of oxygen. You can't make ATP. And you're going to get in some serious trouble
very, very quickly. And so what is the problem? Why are you feeling that pain? Well it really
boils down to glycolysis. And so in glycolysis we're taking glucose. And we're breaking it
down into pyruvate. Remember we net 2 ATP. Where did that energy go? It's being converted
to NADH. A lot of it is converted to NADH. And so NADH is going to be reduced remember.
It's going to pick-up electrons. But pretty soon all of that NADH is full. There's no
electrons that can be donated to it because it's now all at NADH, or reduced NAD+. And
so that's where we get stuck. And where are we going to come up against this wall if we
don't have oxygen or if we don't have mitochondria. And so what is our solution to that? Well
through evolution we've come up with two solutions to this. We have lactic acid fermentation.
And we have alcoholic fermentation. So first you have to do glycolysis. But after that
in animals and bacteria they do what's called lactic acid fermentation. And so in a sloth
they don't move that fast, but maybe in you when you're sprinting or in bacteria when
they're making yogurt, they can do another process after glycolysis. And what that does
is it allows us to keep doing glycolysis over and over again. And in alcoholic fermentation,
they do that by actually converting it to ethyl alcohol. So let's go through those specifically.
Again, here's where we're stuck. We've gone through glucose or glycolysis. We've made
pyruvate. But now we have all of this NADH. And there's no way that we can keep going
through glycolysis because all of it's filled. And so in lactic acid fermentation what happens
is this pyruvate is converted further into lactate. And sometimes you've maybe heard
of that called lactic acid. What happens with the formation of lactic acid? Well we're not
making any ATP. But those electrons can now be converted from NADH and it can be transferred
to lactate. What does that do? It frees up this NAD+ to go back and pick up more electrons
again. And so what we can do is through this process we can go through glycolysis over
and over and over and over again. And so we can make ATP every time we do that. Now we're
not going to get all that ATP that we would if we went all the way through Kreb Cycle,
Electron Transport Chain. But we can still make quite a bit of energy. Now this is a
picture over here of my son. He is a cross-country skier. And so in this picture right here he's
on a treadmill. He's skiing. And this is a test to calculate VO2 max. To figure out how
efficient you are at using oxygen. But it also is going to measure your lactate threshold.
It's going to measure the amount of, how much exercise you have to do before lactic acid
builds up in your muscles in an appreciable amount. And so if you were exercising really
really quickly, you get certain amount of energy through cellular respiration. But if
you go faster and faster and faster eventually your body will also add on top of that this
lactate acid fermentation. And if you've ever run for example a 400 m dash or sprint, that
pain you feel in your muscles is a build up of this lactate in your muscles. And so eventually
that's not even enough. And you're eventually going to just have to stop running or stop
competing because it's too painful. And that's that build up inside your muscles. And so
what happens is after you're done you have go through and breath a lot. And then use
oxygen and cellular respiration to breakdown that lactate. But it does give us kind of
like a turbo boost to go on top of that regular cellular respiration. Bacteria do the same
thing. If you were to put them in milk for example, lactobacillus bacteria will go through
lactic acid fermentation. And that acid breaks down the proteins in the milk and makes yogurt.
And so that's one way that we can survive when we don't have oxygen. Lactic acid fermentation.
Remember, it still includes glycolysis, but it's followed by this lactic acid fermentation
so we can go through that process. Now we also see the same thing in alcoholic fermentation.
And so where would we see that? That's going to be in things like yeast. And so what are
they doing? They're breaking down glucose into pyruvate. But again they're stuck. And
so for example if we put a little bit of yeast and some grain and sugar in this bottle, they're
going to start to do cellular respiration. Just like we do. But eventually they're going
to run out of oxygen. No oxygen can get in this container. Only gas can get out. And
so eventually they're stuck. And they would be stuck if they couldn't do fermentation.
What are they going to do? They're going to convert that pyruvate into ethyl alcohol.
That's the alcohol that we'd find in beer and wine. Now if you look at pyruvate and
ethyl alcohol, we're missing a carbon here. And the reason why is that that carbon is
going to go towards carbon dioxide. That's why we have a build up of this carbon dioxide
in beer or champagne for example. What is that doing though? Again it's the same thing.
It's picking up electrons from NADH. And that's producing more of this NAD+. And so we can
go through that process of glycolysis over and over and over again. And so if we're looking
at yeast inside here, now they'll do alcoholic fermentation. And they'll do that until they
have consumed, built up too much of this ethyl alcohol. And then it will eventually poison
them. And so we've known this for a long period of time. And so fermentation has being going
on for years and years and years. The Egyptians used to make beer using fermentation. And
we do it today as well. So what do you need? All you do is put a little bit of grain in
there, some sugar water and some yeast. If you don't given them oxygen eventually they're
going to convert to alcoholic fermentation. And they'll do that until the level of alcohol
inside there is going to kill the yeast. They settle to the bottom and then we have alcohol.
And so that's anaerobic respiration. What does in do? It allows us to keep going if
we have no oxygen or no mitochondria present. It only lasts for a certain period of time.
And then we're out of luck. And I hope that was helpful.