Back for a third time to take on a topic way too big for a single episode (but they’re going to do it anyway), our hosts Rob Pickels and Trevor Connor are exploring metabolism. It’s a term we’ve all heard. Many of us have complained that we don’t have the same metabolism we did when we were teenagers. But do we really know what this thing is that has slowed down so much?
Metabolism is the sum total of all the processes in our body that use and store energy. Saying it has “slowed down” only means you’re not using as much energy. Go for a long bike ride and your metabolism just sped up. There’s nothing magical about that.
What is magical about metabolism is the remarkably sophisticated machinery inside our cells designed to use energy from carbohydrates and fats. Many of the machines around us, like our cars, use heat energy. That’s not possible in our bodies. Instead, they use chemical energy, where energy is stored by binding molecules together and released by breaking them apart. Inside our cells, the fuels we eat (like carbohydrates and fats) are constantly broken apart—releasing energy that is then captured.
But here’s the cool thing about metabolism. The energy isn’t captured directly by our muscles or heart or brain to power their activities. Instead, it is all captured to do one thing: to produce another molecule called adenosine triphosphate (ATP). It is ATP that is used to directly power everything that happens in our bodies.
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In this episode, our hosts define metabolism and explain this miraculous molecule, ATP. Then they dive into the various machinery that converts our fuels to ATP, including glycolysis, the Kreb cycle, and oxidative phosphorylation.
Don’t worry, this isn’t going to be a deep physiology lecture—we’d need an entire semester just to explain the above three mechanisms. Instead, our hosts are going to go over what you need to know so you can understand when your coach or cycling friend talk about these concepts.
Tune in for the usual humor and off-the-wall facts you probably didn’t know—like how we’re able to use oxygen because a very long time ago a bacteria infected a cell and they ended up liking one another.
So, take a deep breath, and let’s make you fast!
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Episode Transcript
Opening Banter and Framing the Episode as “Science”
Trevor Connor 00:05
Welcome, everybody. This is fast talk your source for the science of, and I’m gonna say today, science,
Rob Pickels 00:11
Science.
Trevor Connor 00:12
Not sure we’re going to talk too much about performance today. So let’s just talk about this is the science of science.
Rob Pickels 00:18
Science.
Trevor Connor 00:19
So Rob, what are we talking about?
Rob Pickels 00:21
Science.
Trevor Connor 00:22
Yes, really? Which means you’re just trying to get through with your cookie and coffee.
Rob Pickels 00:28
Yeah, I will say we are talking about metabolism. But for the past 10 minutes, Trevor has been staring intently at me dipping a chocolate chip cookie into a latte.
Trevor Connor 00:39
You said yourself, you are basically a 12 year old.
Rob Pickels 00:42
No, I said I’m a 42 year old 12 year old.
Trevor Connor 00:46
Yes.
Rob Pickels 00:47
The funny part is on the last dip the cookie broke in half and I’d lost half my cookie is now at the bottom of my latte.
Trevor Connor 00:54
He’s got a spare soggy cookie.
Rob Pickels 00:55
No, no.
Sponsor Message: Polarized Training Certification
Trevor Connor 00:56
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Introducing Metabolism and Why It Is Difficult to Cover
Rob Pickels 01:49
Metabolism, Trevor, this is a big topic.
Trevor Connor 01:51
Yeah. So last time we did one of these basics episode we tried to talk about oxygen delivery, which was ridiculous to try to cover in an hour. So we thought what is an even bigger topic to very inappropriately summarize in an hour and we thought metabolism.
Rob Pickels 02:04
Well, it’s a basic episode, not a shorts episode. That’s a good point, right?
Trevor Connor 02:08
So, we are going to, and look, I’m going to give a big qualifier to start here. They do whole courses on this. As a matter of fact, my major when I was doing my Masters was bioenergetics, which is the study of this. So I spent two years studying this, to try to get this into an hour. Anybody listening who has a background in this, yeah, we’re going to butcher it. We’re going to kind of take this apart, we’re going to get it down to very simple terms…
Rob Pickels 02:35
we’re going to take the meat off the bone like a butcher.
Trevor Connor 02:37
Right. There you go. I like it,
Rob Pickels 02:39
I made that one up on the spot.
Trevor Connor 02:42
Our goal here is not to teach you the details of the biochemistry, which I had to remind myself last night because as I was going through oxidative phosphorylation, I started doing the calculations of how much ATP do you get from X number of hydrogen ions and all that sort of stuff and suddenly went, why am I doing this, this used to be on my test, and I don’t have to do this anymore. So I just want to clarify, we’re not going to dive deep into the biochemistry, what we are trying to do here is just give you some basic understanding. So if your coach starts talking to you about these things, if you hear something about this on the rides, somebody mentioned ATP, or glycolysis, which we do a lot on the show
Rob Pickels 03:22
or oxidative phosphorylation.
Trevor Connor 03:23
Yes, which we’re gonna say a bunch today.
Rob Pickels 03:27
Let’s be honest, everyone, Trevor can’t help himself. I’m here to provide
Trevor Connor 03:33
Rob’s gonna protect you,
Rob Pickels 03:34
translations for you. Simplify things down to normal words that people can understand.
Defining Metabolism and Challenging Common Misconceptions
Trevor Connor 03:41
Rob’s gonna protect you from me. So let’s start. I’m gonna start with kind of a hot take. And Rob, I’m hoping you’re gonna disagree with me. But since this is an episode about metabolism, we gotta define metabolism. And this is something that drives me nuts. Because people talk about metabolism, you see commercials, particularly late night commercials, this is going to ramp up your metabolism and people talking about oh, I’m getting older, my metabolism slows down. Most people don’t know what metabolism is. And so here’s gonna be my hot take. I even looked this up last night, and found plenty of places that define metabolism one way, plenty of places that define metabolism another way. So there’s even debate on exactly what the definition is. But probably the most common definition is metabolism is just the sum total of all the chemical reactions in your body, but I was a bioenergetics major and bioenergetics, if you look up of that definition, it is the subset of the chemical reactions that relates to the transfer of energy. But when I was taking my classes, because it was a bioenergetics course, we had a bias and felt that really that is metabolism. Metabolism is about the sum total of energy transfer in your body. Of using energy and producing, you don’t produce energy, breaks the laws of physics, but you know what I mean.
Rob Pickels 05:01
I concur.
Trevor Connor 05:02
So there is that debate there, is it all chemical reactions, or is it just chemical reactions that are related to energy? But here’s the thing, in our bodies, the way we use energy is with chemical reactions. So think about like a steam engine, you know, the old trains, they got their energy by producing heat. So they just tapped into heat energy, we can’t do that in our bodies. If we tried to tap into heat energy, so you released heat, and then use that heat to power the various processes in our bodies, we basically cook our bodies, so we can’t do that. So we need to use a different type of energy, the energy we use in our bodies is by the breaking of chemical bonds. So you have a molecule that has a lot of stored energy in it. And particularly, we’re going to talk in a second about ATP, which releases a phosphate, and that releases a ton of energy. And then that energy gets collected and used for the different processes in our body. So the human machine is all about chemical energy.
Rob Pickels 06:03
Yeah. And you know, sometimes we expend some energy to store some energy.
Trevor Connor 06:08
Yep.
Rob Pickels 06:08
Right. And that’s the creation and the breaking of bonds. And, you know, it’s kind of like, maybe we take some electricity from the wall, right, and it takes energy to put that into a battery, but then that battery is electricity in the storage form. And we can drain the energy out of that, when we need to use the energy later on for some other process. That’s what we’re talking about inside of the body today is the creation and the storage of energy, and then ultimately, the release of that energy so that we can do work so that we can live, so that we can run, so we can breathe.
Trevor Connor 06:40
So here’s my hot take. And Rob, I was hoping you were gonna kind of argue with this is metabolism is defined as the chemical reactions in our body, since we use chemical energy, and most reactions either use energy or release energy. Really, metabolism is mostly the study of energy, or it’s about energy.
Rob Pickels 07:00
And I concur.
Trevor Connor 07:01
Wow. Okay. I wasn’t expecting that. So…
Rob Pickels 07:05
Well, yeah I mean, I don’t know if you want to simplify it down that much, then yeah, I mean, if we’re talking in a reductionist situation, then energy and the processes that go into creating, storing and utilizing it, I mean, that is metabolism.
Trevor Connor 07:17
We’re going to talk more about reduction and oxidization. And this is where you smack me. So here’s my thing, I get frustrated when people talk about well, my metabolism is slowing down, it’s like this magical thing that happens as we get older. Really, what you’re saying is, I’m just burning less energy
Rob Pickels 07:34
because you’re sitting on a couch.
Trevor Connor 07:36
Yes, when you’re a kid and you’re growing, you need to use a lot of energy, just in the process of growing, if you’re on the couch, you are burning more energy as a kid, because your body’s doing things. As an adult, when you sit on the couch, you’re not burning as much energy, but there’s no magical thing of my metabolism, my energy burning slows down, you’re just being less active. Go for a long bike ride, you just sped up your metabolism. So I hate the term. My metabolism is slowing down, I’m speeding up my metabolism. It’s just you’re burning less or more energy, you want to speed up your metabolism, just go do more work, walk more, exercise more.
Rob Pickels 08:10
Yeah and I think that this is one of the difficulties when words get used in common parlance, you know, in everyday language, that can mean multiple things, right? I think in this situation, when people are saying their metabolism is slowing down, what they could be saying is that their metabolic rate is slowing down. Right. And okay. There are reasons that that might be happening, like Trevor is saying, you could be less active, maybe you have less muscle mass, because you’re getting older, your testosterone is decreasing, your muscle mass is decreasing, because you’re not lifting weights, things of that nature. Then sure, but metabolism itself as a process is not necessarily changing inside of your body.
Trevor Connor 08:49
So get away from this magical view of metabolism of it’s something you had when you’re a kid and you don’t have now.
Rob Pickels 08:55
You can ramp it right back up. And it’s pretty easy to do if you want to.
Defining Calories (Small c vs. Big C)
Trevor Connor 08:58
So I think two other terms that we need to define here. One is calories. Calories is very simple. It’s a measure of energy.
Rob Pickels 09:06
Yeah. And you know how they figure that out? By burning things? Yes, go figure.
Trevor Connor 09:10
So what is the technical definition of calories if you remember this?
Rob Pickels 09:14
It’s the amount of energy, a small c calorie, is the amount of energy it takes to raise one cubic centimeter of water, which is one gram of water, by one degree Celsius.
Trevor Connor 09:27
Nice
Rob Pickels 09:27
And it’s 4.18 and some other numbers, joules.
Trevor Connor 09:31
You remember that pretty well. I’m impressed.
Rob Pickels 09:33
Well, you know, might not be a huge biochemistry person, but I am into energy and the amount of calories you need to complete big giant bike rides. So I do a lot with this. Now, what’s interesting is when we talk about calories, we do not talk about calories. The calories that we talk about are actually 1000 times bigger than that calorie. A big C calorie a kcal. Exactly. And I love online, you know, because I don’t know I post on like slow twitch or whatever else and I’m always making that distinction. And I think that it drives people crazy.
Trevor Connor 10:08
Yeah. But it’s important to say.
Rob Pickels 10:10
It’s huge. Well, when you’re doing calculations, it’s huge. Right?
Trevor Connor 10:12
Exactly.
Rob Pickels 10:13
Yeah.
ATP as the Body’s Energy Currency
Trevor Connor 10:13
And then the last really important thing to understand is still, let’s see if I can remember this off the top of my head, adenosine triphosphate.
Rob Pickels 10:22
ATP. Yes.
Trevor Connor 10:23
ATP is the energy currency in our body. So, you think about carbohydrates, fats, we consume those that gives us our energy. But nowhere in the body are you directly taking the energy from carbohydrates or fats, and using them to power anything, to move your muscles to keep your heart beating, anything like that.
Rob Pickels 10:45
Yeah, this chocolate chip cookie, and my latte is not plugging into my muscle and helping me run.
Trevor Connor 10:50
So what actually happens is, those fuel sources are broken down, the energy is released from them. And then the energy is trapped and used to create ATP. And then that ATP, we store a very small amount of ATP in our body, so we’re constantly reproducing it. So basically, you have ADP, adenosine diphosphate. And then you have a phosphate group that are floating around, you release – and so let’s say you consume a bunch of glucose, that glucose, and we’ll explain how in a second, is processed, it releases energy, that energy is used to bind that phosphate to the ADP to produce ATP. And that’s constantly constantly even when you’re sitting on the couch happening in your body. And then when your muscles need to work, when anything needs to happen in your body that requires energy, it basically grabs in ATP releases the phosphate from the ATP, that releases the energy and then that energy is used directly.
Rob Pickels 11:46
Right. And so in this situation that Trevor is describing, ATP, going back, that’s adenosine triphosphate. So we have an adenosine molecule, this sort of the backbone, and then tri stands for three, we have three phosphate groups attached to that, when Trevor mentioned ADP, D is in dog, D as in doorknob, D is in delta. Delta, I think is the right word, then that stands for two, it’s an adenosine with two phosphates on it. And there’s also an AMP, a mono, a one phosphate, adenosine as well.
Trevor Connor 12:19
Yep. So I think an easy visual to think of this as is ATP is your body’s battery. So, you want to power anything in your house, got to plug a battery into it, so that’s the ATP. Glucose, fat, all these fuels that you consume, their job is to charge the battery, they’re not the battery themselves. They just charge the battery, they keep your batteries charged up so that you can power the various things in your body. That’s the way to think of it.
Limited ATP Storage and the Need for Continuous Resynthesis
Rob Pickels 12:47
Sure is.
Trevor Connor 12:48
That work? You haven’t argued with a thing yet.
Rob Pickels 12:50
I know.
Trevor Connor 12:50
This bummed about your cookie and your coffee…
Rob Pickels 12:53
my cookie laden latte hasn’t kicked in yet.
Trevor Connor 12:57
Any other things that we need to cover to give terminology on that ATP one is really important, because that is the direct fuel of our body. So last thing to understand here of how important this is, and how much we have to keep rebuilding this ATP, we don’t store a lot of ATP or ADP in our body, because it’s actually molecularly very heavy, so we don’t want a ton of it. So at any given time, we have about four ounces of ATP slash ATP in our body, it’s not a lot. If you ran a marathon, you would produce about 80 kilograms of ATP. And it’s not that you’re bringing in new ADP or new ATP, it’s just you’re constantly having this cycle of ATP releases the phosphate, becomes ADP and a phosphate, and then we recharge it, bind the mat together, and then they’re used again, so just this constant cycle. But as you’re running as you’re working out, as you’re going for a bike ride, you’re just constantly constantly constantly rebinding to produce the ATP and then binding to release the energy for whatever process that just happens over and over and over again.
Rob Pickels 14:05
Right, and to put that into real world terms. If you just from a standing stop, sprint at maximum speed and you only relied on the ATP stores that you have in your body, you do nothing to replace them, you don’t start metabolism to recharge these batteries, you have less than two seconds worth of ATP energy stored in your body at maximal effort. And if you are just going in a base sort of a zone two effort then you have about 15 seconds worth of ATP stored in your body. So, immediately we have to be starting this metabolic process to begin recharging those batteries.
Trevor Connor 14:41
They need like lithium ion technology man we have moved on like we have good battery storage now. So go over that battery analogy is basically like you have batteries that last 10 seconds.
Rob Pickels 14:52
Lame.
Trevor Connor 14:53
So you got to kind of be charging them as you’re using.
Rob Pickels 14:56
Exactly, yeah.
The Phosphocreatine System as an Immediate Energy Source
Trevor Connor 14:57
Okay, so we’ve talked about ATP and how we have a very short storage of ATP that we can use immediately. I think before we dive into our primary fuels of glucose and fat, there is one other short form, again, it doesn’t last very long, but it can provide you with very immediate energy and only lasts. Again, it’s measured in seconds. And that’s phosphocreatine.
Rob Pickels 15:23
I spent a lot of time as a high school sprinter. Going to GNC and taking creatine. It’s just what you do.
Trevor Connor 15:30
Because you were told to do it.
Rob Pickels 15:31
That’s what you do. Yeah. So what the heck does that do? Well, the creatine molecule is bound to phosphates. And as you know, we’ve been talking about these phosphates, well, in our body there is a very simple process to replace one of the phosphates on to ATP, to make ATP useful again for our muscles and maintaining cell membrane potentials, all of that. And that is literally to steal one of the phosphates off of creatine and add it back to ATP. It’s a two step process, which is very fast. But as we’ve realized, in the theme of this episode, right, the fastest processes seem to have the least amount of storage. And that’s the same with the creatine that we have in our body. We all have creatine naturally in our body, but through supplementing exogenous creatine, drinking that five, you know, five grams of creatine with your carbohydrate, then you’re able to put some more of that storage, it’s like eating little batteries, if you want to think of it that way, maybe a little safer, tastes bitter, just like batteries do, anyway, then you can have a little bit more of that storage in your body. And we talked before that the ATP that we have is maybe just a couple seconds worth of storage, by adding more creatine phosphate, we get a couple more seconds worth of storage, right. So, if you’re doing a 100 meter, 200 meter, or maybe a 400 meter dash, you get a few more seconds before the rest of your metabolism has to kick in. In maybe this is or isn’t beneficial for endurance athletes who are going for hours. You know, there’s certainly some research that says it’s beneficial, there are some that say it’s not, that is not the point of this episode. What you need to know from this is that this is a very fast system that only lasts for a couple seconds at a time.
Trevor Connor 17:29
It’s a one step process.
Rob Pickels 17:31
You got it baby.
Trevor Connor 17:32
So yeah, so we are talking about the prioritization here, you’re going off the gun super fast, you’re initially relying on that stored ATP. And the thing that’s gonna ramp up the quickest is the phosphocreatine system.
Rob Pickels 17:47
Correct.
Trevor Connor 17:48
Just going to continue to produce energy while you’re ramping up the other systems. So it is an important one. And, you know, I’m glad you brought back up the phosphate, I just want to take a quick second to just emphasize that, that what biology has discovered, or evolution has discovered is this phosphate bond, that takes energy to bind. But when that bond is broken, it releases a lot of energy. So it’s just a great way of storing energy and releasing energy. So you’ll hear physiologists talk all the time about phosphorylation, and this is what they’re talking about.
Gender Differences in Metabolism and Research Limitations
Rob Pickels 18:22
There you go. Now one thing to point out before we move on here is, let’s be honest, the vast majority of research has been on male subjects. And while the process is the same between men and women, right, the breakdown of carbohydrate and the chemical process that causes you know, the phosphate to be added back to create ATP. While that is the same between sexes, we do have to recognize that when we look at the output of metabolism, it is a little bit different in men and women, right. Because women have different levels of hemoglobin, different levels of muscle mass, different enzyme concentrations, so on and so forth. So we have been talking about kind of a female specific episode. Hopefully we get that out at some point in the near future. This is a very generalized conversation, and there really needs to be more research and more education on the female specific side of things.
Differences in Fat and Carbohydrate Utilization Between Men and Women
Trevor Connor 19:15
That’s a good segue to what we’re about to talk about. Because one thing we do know for certain is women are better at using fat to recharge their ATP.
Rob Pickels 19:23
Correct.
Trevor Connor 19:24
And men have a little better ability to use glucose.
Rob Pickels 19:27
For the same relative workload, females, for the most part, as generalizations can be, are going to be oxidizing more fat than a male is that that same relative workload.
Trevor Connor 19:36
Yep. So let’s shift gears there and let’s talk about our primary fuels. And again, even though these are the fuels remember, we don’t directly use fat carbohydrates or protein to power anything. All they are being used for is producing ATP. That is it. And there’s a loss of efficiency when you do this. So, for example, with carbohydrates, if you look at the stored energy in a glucose molecule, only 34% of it actually goes into the ATP.
Rob Pickels 20:07
Okay.
Trevor Connor 20:08
So it’s not 100% efficient, not even close.
Rob Pickels 20:11
No, no.
Trevor Connor 20:12
That’s a little more efficient fats 40%. But another way to look at this is, so for example, if you take a mole of glucose, you still haven’t smack me down for using these terms.
Rob Pickels 20:21
That’s fine, I’ll tell them what a mole is later.
Trevor Connor 20:23
Yeah, don’t worry about a mole. Moles are confusing. But we’re just talking about a mole of glucose. If you take a mole of glucose it has, so if you actually burn that mole of glucose, you would produce about 630 kilojoules.
Rob Pickels 20:32
I suddenly want avocados.
Trevor Connor 20:33
Why avocados?
Rob Pickels 20:33
Somebody else wait, somebody out there…
Trevor Connor 20:33
Like sweetish fish or something like that.
Rob Pickels 20:38
No, no, no. Somebody out there is gonna get that joke and it’s gonna be really funny to the one person on the internet who understood what I just said.
Trevor Connor 20:48
Yeah, I didn’t get that.
Rob Pickels 20:49
That’s okay, I’m not even going to explain it to you.
Trevor Connor 20:52
So, but if you take a mole of glucose…
Rob Pickels 20:56
Avocados.
Trevor Connor 20:57
Oh boy, we’re not gonna get passed this.
Rob Pickels 21:00
No we’re not.
Trevor Connor 21:01
I’m just gonna pound through it. So about 630 kilojoules. When that glucose is fully oxidized, the equivalent energy that goes into ATP is only about 200 and something kilojoules. So that’s what we mean by loss of efficiency. So that other 400 kilojoules is lost as heat.
Rob Pickels 21:21
Sure is. Stinks, doesn’t it?
Trevor Connor 21:23
Yeah, it does.
Rob Pickels 21:23
Man.
Trevor Connor 21:24
And this is why you get hot when you work out.
Rob Pickels 21:26
I know, anyway, so fat?
Fat Metabolism: Storage Capacity, Efficiency, and Limitations
Trevor Connor 21:27
Yeah, so let’s go through our fuel sources. Want to start with fat?
Rob Pickels 21:30
I want to start with fat, but I want you to start and I’ll tag on.
Trevor Connor 21:33
Okay. Fat, it is our largest energy source.
Rob Pickels 21:38
Might be your largest energy source.
Trevor Connor 21:40
Oh boy, says a guy who’s eaten a cookie on a coffee. So fat is our most efficient energy source.
Rob Pickels 21:52
It’s our most abundant.
Trevor Connor 21:54
It is definitely our most abundant. So let’s just for a minute, kind of compare carbohydrates and fat here. If you take a you know, there’s different types of fat molecules, and they’re all going to produce different amounts of ATP. But you take a single triglyceride, hesitated there with single because triglyceride as the name says, it’s actually a glycerol bound of the three fatty acids. So it’s actually…
Rob Pickels 22:18
Three mmm sorry.
Trevor Connor 22:19
But you can produce over 400 ATP from triglyceride. You take a glucose molecule, and you only get 32 ATP.
Rob Pickels 22:29
That’s it.
Trevor Connor 22:30
So this is a big debate, if you want to get really science geeky, some people say 34, some people say 36, I go at the 32. Because while you do actually produce, I think it’s 36 ATP, you have to use 4 ATP to produce it. So the net is 32.
Rob Pickels 22:46
Got to spend money to make money, Trevor.
Trevor Connor 22:48
Exactly. So we’re looking at what you have total at the end. So this single molecule of fat produces significantly more ATP than the single molecule glucose.
Rob Pickels 23:00
Sure does.
Trevor Connor 23:01
And the other thing is, glucose is heavy. Again, you can’t store that much without putting on a lot of body weight. Because we store it as glycogen, and a single glucose molecule has to be bound to 4 molecules of water. So you just can’t store that much. So as a result, we store I think it’s about 2000 calories in our body of of glycogen of glucose.
Rob Pickels 23:24
Yeah, it’s roughly depending on the gender, the size of the person, it’s roughly 400 calories in your liver. Liver glycogen is interesting, because it can be sent anywhere in the body, it can be hit the bloodstream, with the balance of that being between 1200 and 1600 calories in your muscles, right. So that really depends on the amount of muscle mass you have is how much glycogen you’re storing in your muscles. But what’s really interesting about that, and I don’t want to get too far off topic, is that once it’s in your muscle, it is stuck in your muscle. So if you’re out riding your bike, all that glycogen in your tricep is doing nothing to help you pedal your bike. So whenever we’re doing calculations on say how much energy you ought to be consuming during an event, we have to limit it to the amount of glycogen that you have in the working muscles, because that’s all that really matters.
Trevor Connor 24:12
Right. So the way to think of it is you have enough glycogen. If you were running a marathon, it wouldn’t even get you through a full marathon.
Rob Pickels 24:20
No, absolutely not.
Trevor Connor 24:21
Give you maybe a little over an hour, because you’re not going full. You’re going below threshold, but it won’t get you through a marathon. So now let’s talk about fat. And let’s stick with a lean athlete, because obviously, people are really going to vary, but you have somewhere in the neighborhood of about 100,000 calories…
Rob Pickels 24:37
Right.
Trevor Connor 24:38
In fat. So you have enough, even a lean marathon runner has enough fat to power them through about 40 marathons.
Rob Pickels 24:44
Yeah, you know, and this fat is stored in a few different places, right. We have the subcutaneous fat that we all think about when you pinch your belly, you know, you get a nice little handful of fat there. We also have some fat around our organs. Maybe that’s not touched as much for fueling exercise. And then we also have some fat stored in our muscles itself called intra muscle triglycerides as well, that can potentially be a fuel source for people.
Trevor Connor 25:09
Yep, exactly. So it is our primary fuel and relatively speaking, it’s light, we can store a lot of fat. You have, you tried to store 100,000 calories in glucose, you wouldn’t be able to walk. You’d measure your weight in tons.
Rob Pickels 25:24
If I ate that much, I wouldn’t want to walk. Yeah.
Trevor Connor 25:26
That’s a great point too. So, it’s a great fuel source, but here’s the issue. Fat is slow burning.
Rob Pickels 25:34
It’s hard to break down giant molecules.
Trevor Connor 25:36
It is hard to break down. Plus, you don’t store very much in the muscles. It has to be transported. And because fats and water don’t really like one another, it’s actually very hard to transport the fats to the working muscles. There’s a whole bunch of processes that we’re not going to go into too deeply today.
Rob Pickels 25:58
You stopped? Are you okay?
Trevor Connor 26:00
Yeah, I want to say albumin, but I’m not gonna say it.
Rob Pickels 26:02
Oh, it’s fine. You can say albumin. I’m losing a little bit of albumin right now. So yeah, my kidneys are… it’s all right.
Trevor Connor 26:08
So you’re glucose dependent right now?
Rob Pickels 26:10
Why not? Man? Why not? Let’s just eat cookies and lattes all day.
Trevor Connor 26:14
But I think we actually covered this in one of our science episodes.
Rob Pickels 26:17
What?
Trevor Connor 26:17
One of our review episodes where we talked a little bit about all the steps to get fat into the working muscles and how difficult it is.
Rob Pickels 26:25
Maybe, I don’t quite remember, I think it’s interesting that lipolysis, the breaking down of fat, can actually exceed the transport and the oxidation of fat. So the issue isn’t breaking the fat down for energy, it’s actually taking those molecules and utilizing them.
Transition to Carbohydrates and Rapid Energy Production
Trevor Connor 26:42
So, I was feel like we should shift, before we finished talking about fat, we should shift to carbohydrates.
Rob Pickels 26:48
Let’s do it.
Trevor Connor 26:49
And talk about how quickly those can be broken down.
Rob Pickels 26:52
Quite.
Trevor Connor 26:53
And that’s really your benefit of carbohydrates. Fats, unlimited, but it is very complex on the processes it takes to finally produce your ATP from fat. So you can go forever on fat, you just can’t go fast. Glucose is different. And so here’s another hot take. And Rob, you know, one of my favorite old textbooks is the “McArdle Katch & Katch” book. And I was going back through, so actually, when they’re newer editions, I think the ninth edition, I don’t know if that’s the newest or not, but I was reading that last night and they started talking about aerobic and anaerobic glycolysis. And I started grinding my teeth, because I hate those terms.
Rob Pickels 27:31
Sure.
Trevor Connor 27:31
And I was so appreciative after they explained that they said, and we kind of feel those terms aren’t appropriate. And we’d rather use slow and fast glycolysis.
Rob Pickels 27:41
Okay.
Trevor Connor 27:42
That’s like, thank you.
Rob Pickels 27:43
Yeah.
Trevor Connor 27:44
Thank you for switching the terms.
Rob Pickels 27:45
Yeah.
Glycolysis Overview and Terminology Clarification
Trevor Connor 27:46
So we’re gonna get to this in a minute, but when you are breaking down these fuels to produce ATP, in every cell, you have processes that break it down, and the anaerobic side is your glycolysis, which only works on carbohydrates. Then, that happens outside of the mitochondria, so it just happens in what’s called the cytosol. The regular fluid of the cells.
Rob Pickels 28:10
The swimming pool.
Trevor Connor 28:11
Yeah, the swimming pool. Then you have your mitochondria. And inside the mitochondria, you have the Krebs cycle, and oxidative phosphorylation, and that’s where aerobic metabolism happens. And that’s where you continue to break down glucose. And you also break down fats.
Rob Pickels 28:26
That’s like Uncle Bob floating in the pool noodle.
Trevor Connor 28:29
Yes.
Rob Pickels 28:30
Yes.
Trevor Connor 28:31
And so here’s the thing. Glycolysis is really fast. It’s just 10 steps. So you can produce ATP from glycolysis really quickly.
Rob Pickels 28:39
Correct.
Trevor Connor 28:40
But you can only produce it from glucose. And it is anaerobic. It requires no oxygen.
Rob Pickels 28:44
Yes.
Trevor Connor 28:45
At no point in glycolysis do you need oxygen molecules. But you take a glucose molecule and you break it down in glycolysis. you’re producing 2 ATP. It’s not a lot.
Rob Pickels 28:56
Nope.
Trevor Connor 28:57
So it’s fast. But it doesn’t give you a ton of energy.
Rob Pickels 29:00
Yep. And it actually takes 2 ATP. It produces for ATP, but it took 2 ATP…
Trevor Connor 29:05
Right.
Rob Pickels 29:05
So that’s where you get to Trevor’s net to ATP. And when we’re talking fast, we’re talking, this is able to be activated in milliseconds.
Trevor Connor 29:15
Yes.
Rob Pickels 29:16
And you can see the end product of glycolysis, which is lactate. You can see lactate begin to accumulate within one second of the onset of workload.
Trevor Connor 29:27
Yep. So if you are doing 100 meter sprint, the first few steps, you’re relying on the stored ATP.
Rob Pickels 29:35
Yep.
Trevor Connor 29:35
By the end of that sprint, you’re relying on glycolysis.
Rob Pickels 29:39
Yes. At the, oh, I’m totally… I read this, the last… well okay, I’m jumping ahead a little bit. The last five seconds of a 32nd all out sprint are 50% aerobically fueled.
Trevor Connor 29:54
Yeah.
Rob Pickels 29:54
By that point. Interesting.
Trevor Connor 29:56
Even glycolysis can’t keep up and very quickly you hit a point where aerobic metabolism ramps up, and you’re using a lot of energy from aerobic metabolism. But we’ve talked about this on the show and as we go through this and talk about these various processes, really important to understand is, you’re not exclusively using one.
Rob Pickels 30:15
Correct. Never.
Trevor Connor 30:17
Ever. Yeah, I think the closest would be like, if you’re doing a sprint, that first step or two might be, almost completely stored ATP, will you just ramp up the processes.
Rob Pickels 30:27
Functionally the contribution is stored ATP, but you are initiating all processes…
Trevor Connor 30:34
Right.
Rob Pickels 30:34
Aerobic, anaerobic, if you want to call them that, from that first step, your body is flipping all the switches, just some of these systems take a little bit longer to warm up and get going than others. And so their contribution kicks up later.
Trevor Connor 30:47
Exactly. But you’re always using a mix of all of them.
Rob Pickels 30:50
Yep.
Trevor Connor 30:51
So that’s the fast part of glucose breakdown.
Rob Pickels 30:54
Yep.
Trevor Connor 30:55
Then I will explain all this in a minute. The end product or glycolysis, which is pyruvate. Or lactate,
Rob Pickels 31:03
If you talk to Anago Similan is always locked in.
Trevor Connor 31:05
Which I agree with. But I’m going with what a lot of people like to say. Yes, because it has to be converted to lactate in order to go into the mitochondria, and then it gets converted back to pyruvate.
Rob Pickels 31:15
Yep.
Trevor Connor 31:16
But that then moves into the mitochondria, goes into what we’re going to explain in a minute, the Krebs cycle and oxidative phosphorylation.
Rob Pickels 31:25
Yep.
Trevor Connor 31:26
And then you produce another 30 ATP, it just takes longer.
Rob Pickels 31:32
Sure does.
Trevor Connor 31:32
And that’s the slow phase.
Rob Pickels 31:34
And to put that into perspective, we’re talking a one to two minute ramp up. Right, and we see this, you can see this in your heart rate, you can see this in your oxygen consumption, if you’ve ever had like a vo2 max test. When we change workload, when we go from 200 Watts to 225 Watts, that initial bump in our ability to produce 225 Watts, the initial energy needed, is supplied by the fast glycolysis. And you can watch the oxygen ramp up second by second for another minute or two until it flatlines and remains relatively steady. That’s the lag period that the slower glycolysis needs to work aerobically.
Trevor Connor 32:21
Yep. So the other interested thing here to understand about carbohydrates or glucose, it is the only fuel that can produce ATP both anaerobically,
Rob Pickels 32:33
without oxygen,
Trevor Connor 32:34
and aerobically
Rob Pickels 32:36
with oxygen.
Trevor Connor 32:36
Right. Fat can only produce ATP, aerobically. So protein, well, who cares? There’s some amino acids, I guess, can, well they don’t go into glycolysis, but they are converted to remember to pyruvate.
Rob Pickels 32:52
I don’t think we should get into it. Just like I don’t think we should get into other sources of energy like alcohol, come on, man, and I don’t want to do it.
Trevor Connor 33:01
I don’t have a coffee. I don’t.
Rob Pickels 33:04
Coffee is a different type of energy. Also, there’s ketones. And I don’t want to get into that today. Because we did an amazing episode with Brendan Egan. I don’t remember, 30 episodes ago, 40 episodes maybe at this point. Really great explainer on ketones, how they’re utilized for energy and whether or not supplemental ketones, exogenous ketones, are worthwhile. So go check that out. If you’re interested in ketones.
Protein as a Fuel Source and Why the Body Minimizes Its Use
Trevor Connor 33:28
So I’m gonna give just one more protein, I think we just need to cover it quickly. And then, say, from this point foward we’re really just going to talk about carbohydrates and fats.
Rob Pickels 33:37
You do you, I’m going to drink my cookie.
Trevor Connor 33:39
Please do. Protein is a fuel source, but our body doesn’t like to use it as fuel. Amino acids have much more important roles as functional roles in our body. So both structural, and as messengers. So our body prefers to use them for those purposes, even when it breaks protein down for fuel, it gets them into the Krebs cycle. It’s hard work. It takes a lot of energy because there’s a nitrogen bound to proteins, that’s part of what defines a protein, or an amino acid, and you have to do something with that nitrogen when you break it down. So what you will see is when we start becoming depleted in glucose, our body might start converting, so it’s called gluconeogenesis, converting some amino acids to glucose to keep the steady supply going. But it really doesn’t like doing that because it takes energy, and you have to process those nitrogen. So it’s only going to do that when it has to.
Rob Pickels 34:36
And that’s what you might see, but what you might smell is ammonia. So if you’ve ever been out on a ride where you haven’t appropriately fueled or it’s a really long ride, and you’re not bringing enough food, and you’re like man, I kind of smell like Windex.
Trevor Connor 34:50
Yes.
Rob Pickels 34:51
That’s ammonia, right? Well, this is why. And so hey, people, make sure you’re eating enough carbohydrate.
Oxidative Priority of Fuels (Carbohydrates, Fat, and Protein)
Trevor Connor 34:57
Yep. If you haven’t been feeling correctly. So last thing to say on the different fuel sources is, there’s what’s called oxidative priority. So when you consume a mix of these, your body is going to prioritize which it breaks down first, which breaks down second, which breaks down third, and the priority goes carbohydrates, then fat, then protein. Now, there’s debate of whether alcohol is a carbohydrate or its own fuel. But it definitely is highest in the oxidative priority. So what that means is, if you consume a mixed meal, you’re going to use those carbohydrates for fuel. And if that’s supplying your needs, it’s going to take all that fat and say, well, we don’t need this right now, because we’re fueling off of the carbohydrates. So we’ll just store the fat. So you know, people eat a meal and go, oh, you know, I’m converting all these carbs to fat, you can convert. I don’t know if we’ll go into this today or not. But the inner conversion is actually not very good in the body. So actually, what’s happening is you’re just prioritizing using carbohydrates, and you’re storing the fats you consume. So it kind of looks like you’re converting, but you’re not really. Does that make sense?
Rob Pickels 36:05
Yes.
Trevor Connor 36:06
I got a thumbs up from Rob. Have you ever given me a thumbs up before?
Rob Pickels 36:09
No.
Trevor Connor 36:10
Are you ever gonna give me one again?
Rob Pickels 36:11
No.
Trevor Connor 36:13
Just that one time?
Rob Pickels 36:14
Yes.
Trevor Connor 36:15
All right. So now let’s go into the hard part where I’m going to be biting my lip not to get…
Rob Pickels 36:21
No, man, go for it. Go for it. I’ll bring the people back to reality. It’s fine. You do you.
Overview of Cellular Energy Pathways
Trevor Connor 36:26
Okay, fair enough. We just talked about our fuel sources. So now we’re going to talk, and we’ve already mentioned it a little bit, about, for lack of better word, the factory. The place where those fuel sources are taken, broken down, and used to produce ATP. So, this is, we already talked a little bit about glycolysis, Krebs cycle, oxidative phosphorylation, you’ve probably heard these terms, you might have studied them in high school chemistry. If you’re an exercise physiologist, listening to the show, then you studied it to death and wondering why you’re listening to this episode. But we’re gonna give you the basics of what you need to know about these.
Rob Pickels 37:04
Well, Trevor, should we move to more glycolysis?
Trevor Connor 37:08
So let’s explain this. And there is one other thing that we need to quickly explain. And I’m gonna see if I can do this with an analogy, it’s kind of fun. All this is driven by enzymes.
Rob Pickels 37:19
Okay.
Enzymes and Rate-Limiting Steps in Metabolism
Trevor Connor 37:19
And I’m sure people have heard the term enzyme and what are enzymes. So this goes back to, this is why the body doesn’t like to use protein for fuel, because enzymes are just proteins.
Rob Pickels 37:30
They are proteins.
Trevor Connor 37:31
And enzymes, I think the correct term would be, speed up processes. So I’m going to use an analogy here, that could kind of be fun to try to explain enzymes as simply as possible. So if you’re in a factory, and you have a nut and a bolt, and you put them on the floor. If you think of that analogy as the factory is the body. Strangely enough, you leave that nut on the bolt on the floor long enough, the nut will screw itself onto the bolt.
Rob Pickels 38:00
If you put enough monkeys in a room, they will write Shakespeare, eventually.
Trevor Connor 38:04
But here’s the weird thing. So when you’re talking about binding chemicals together, if you put them in the same chemical meal you together for long enough, they will eventually bind together, and they will eventually break apart. That happens on its own, it just happens really slowly. So it’s like I said, it’s this weird thing that if you just put the nut and the bolt on the floor, eventually that nuts going to screw onto the bolt at some point. And it might screw itself off at some point. Think of an enzyme as a little factory worker who comes in picks up the nuts and bolts and just screws them together. Makes it happen much more quickly.
Rob Pickels 38:41
I don’t… I see where you’re going with this,
Trevor Connor 38:44
Oh, like the analogy?
Rob Pickels 38:45
I don’t know that I like the analogy. But the most…
Trevor Connor 38:47
I thought it was is pretty good!
Rob Pickels 38:48
The most important point that you’ve made that we haven’t pointed out is that these processes are just kind of happening as they float around in the cytosol. Right, that as long as we have enough of piece number one and enough a piece number two, they eventually bump into each other with the help of an enzyme. And the process happens. It’s not like this is an orderly sort of thing that’s occurring.
Trevor Connor 39:10
Right. But you know, that was important thing I always learned about enzymes is the enzyme isn’t making a reaction happen, that wouldn’t happen otherwise, it’s just dramatically speeding up the reaction. So you have these two chemicals, use that example, they’re just floating around this milieu. As I said, at some point, they might bind together, but the enzyme literally kind of grabs one grabs the other and goes, I’m going to put you together. And I’m going to make it happen really quickly. Still struggle with that aren’t you.
Rob Pickels 39:36
I am.
Trevor Connor 39:36
I see the look on your face.
Rob Pickels 39:37
It’s not wrong. Anyway, move on.
Trevor Connor 39:40
This goes back to we’re trying to put this in simple terms, Rob.
Rob Pickels 39:44
Moving on.
Trevor Connor 39:46
We’re moving on. So the important thing is, every step in these processes that we’re going to talk about has a enzyme that is involved in that step. An enzyme that makes that step happen.
Rob Pickels 39:58
Yep.
Trevor Connor 39:59
And that becomes really important because if you don’t have an availability of a particular enzyme, that’s going to affect how quickly this can happen. So every process has what’s called a rate limiting enzyme. So glucose, the rate limiting enzyme is something called phosphofructokinase. So PFK, the availability of PFK is going to determine how quickly glycolysis happens. I just thought the really important from a health standpoint, it does control the breakdown of glucose. It doesn’t control the breakdown of fructose, because fructose enters glycolysis, right below PFK. So when you process fructose, you are processing it very rapidly, whether you need it or not.
Rob Pickels 40:44
Do it.
Trevor Connor 40:44
So that’s great when you’re exercising because you get rapid fuel. You’re sitting on the couch eating a lot of high fructose corn syrup. It’s not a good thing. Not a good thing. Because the body doesn’t know what to do with it.
Rob Pickels 40:57
I agree.
Trevor Connor 40:57
Do you want to correct me on enzyme? So it’s what’s your analogy? What would you use?
Rob Pickels 41:01
I’m good. I don’t need to spend more time on it.
Trevor Connor 41:04
I would throw up a thumbs up from Rob to he’s got his head at him…
Rob Pickels 41:08
I’m just some complacent at this point.
Glycolysis in Detail: Location, Steps, and ATP Yield
Trevor Connor 41:11
Trevor, you ruined this episode. I’m done with it. Okay, so shall we talk about glycolysis?
Rob Pickels 41:19
Do it.
Trevor Connor 41:19
Glycolysis has 10 steps. It’s in the cytosol. Look, I’m going to tell you, when I took my first physiology class I remember going into my final exam. And one of the questions was What part of the cell is glycolysis happening and then had like the cytosol mitochondria at at a bunch of different locations. And I remember reading that question. That’s such a nitpicky question, why would we care? And as I learned more and more about physiology, I’m like, that’s a really important question. Because glycolysis, we want it to be quick. And as we’re going to talk about in a second, getting things into the mitochondria is hard. Getting things out of the mitochondria is hard. That slows things down. So it’s really important that glycolysis happens out in the cytosol. So that you can produce, not only produce the ATP quickly, but the ATP can get to the parts of the cell that need to use it really quickly, too. So that’s actually kind of important. So it’s 10 step process, doesn’t use oxygen. So it’s anaerobic. Doesn’t produce a lot of ATP. As we said, breakdown of a glucose molecule in glycolysis only produces a total, a net total, of two ATP. What else do we need to say about glycolysis?
Rob Pickels 42:34
Well, Trevor, you’ve talked about enzymes, you talked about the fact that glycolysis actually consumes ATP. And I just want to point out, the reason that glycolysis consumes ATP is because those enzymes actually need some energy, to activate themselves to do the work that they have to do, right. So I’m just trying to tie those two concepts together for people. And we can’t go back on those steps. Once those steps have occurred, it’s not like we can back up to the molecule that we had before in the breakdown, the conversion, of glucose molecule into ultimately a pyruvate, or a lactate, or actually, I should say, to pyruvate, or to lactates. From each glucose molecule.
Trevor Connor 43:21
Though is important to point out most of glycolysis can reverse and that’s actually how we produce glycogen.
Rob Pickels 43:27
Correct. Different enzymes, though, to go backward than enzymes to go forward.
Trevor Connor 43:32
Right. But one other important thing on that note to be aware of is, as you pointed out, it takes ATP to get it moving. Re the first two steps, you need ATP, to actually use ATP to break down glucose before it starts producing ATP. Glycogen enters the process right below that first step. You only have to burn one ATP to break down glycogen.
Rob Pickels 43:57
Sure.
Trevor Connor 43:57
So, when you are getting the fuel from glycogen, you actually produce three ATP when you’re getting it from glucose, you’ve only produced two.
Rob Pickels 44:06
And there you go.
Trevor Connor 44:07
So advantage to be producing glycogen when you’re at rest.
Rob Pickels 44:10
Well, Trevor, let’s take this from a glycolytic process to an oxidative process. But still, let’s talk about carbohydrate.
Mitochondria and the Constraints of Aerobic Metabolism
Trevor Connor 44:19
Yes. So now we’re getting into the mitochondria. Should we talk about what those are?
Rob Pickels 44:25
Mitochondria?
Trevor Connor 44:26
I think they’re cool.
Rob Pickels 44:26
I think you’re gonna compare it to a powerhouse, a factory, an energy plant. And Uncle Bob floating in a pool in a pool noodle thing.
Trevor Connor 44:35
That’s so 1990s. I gotta go cooler. I gotta go evolutionary biologist on this.
Rob Pickels 44:40
Wow. Okay.
Trevor Connor 44:42
The theory here is that…
Rob Pickels 44:44
Oh, you’re going there?
Trevor Connor 44:45
I’m going there.
Rob Pickels 44:46
Oh my god he’s going there.
Trevor Connor 44:50
Original cells, eukaryotic cells were anaerobic.
Rob Pickels 44:55
Yep.
Trevor Connor 44:55
They couldn’t use oxygen for fuel.
Rob Pickels 44:58
Correct.
Trevor Connor 44:58
And the belief is that bacteria were the first things to figure out how to produce energy using oxygen. And at some point, bacteria got inside a eukaryotic cell and said, Hey, we kinda like being together. Let’s keep doing this.
Rob Pickels 45:16
Symbiosis.
Trevor Connor 45:17
Symbiosis. And that bacteria eventually evolved into mitochondria, which is why mitochondria actually has some of its own DNA.
Rob Pickels 45:27
Yeah, interestingly, too, if we want to switch this to genetics, your mitochondria come from your mom. Which is fortunate for my kids, because Melissa, my wife, great distance runner, me not so much. So you know, they stand a chance moving forward.
Trevor Connor 45:43
Yes. So if you are a great aerobic athlete, thank your, mom.
Rob Pickels 45:46
Thanks, Mom.
Trevor Connor 45:47
If you are a horrible aerobic athlete, blame your mom.
Rob Pickels 45:50
Thanks, Mom.
Trevor Connor 45:51
Dad had nothing to do with it. So, yes. So mitochondria has some of its own DNA, but here’s another and I’m going to simplify a little bit. But really important thing to understand about mitochondria, is that’s where your aerobic metabolism happens. So you’ve heard about antioxidants and oxidants. It’s called oxidants. Because oxygen is a very powerful oxidant, it can do a lot of damage to your body. So when you are producing energy, aerobically, you’re producing a whole lot of oxidative stress. And your body needs to learn how to deal with this. And one of the ways you do it, if you look at mitochondria, it actually has an inner membrane and an outer membrane. And it really kind of keeps the whole system locked up. So you have very low pH in there it’s very acidic environments, between the two membranes, you have a lot of oxidative stress to deal with in there. But it keeps it mostly in the mitochondria, which helps protect the rest of the cell. And that’s important because if you were trying to do these processes in the cytosol of the cell, you could really damage the cell. And this is part of why this aerobic metabolism is so slow, because, think of mitochondria like a Fort Knox, it doesn’t allow much to get transported in, it doesn’t allow much to be transported out, and you got two membranes to cross, and a really acidic environment between those two membranes. So it takes a lot of work to actually move things in, move the fuel into the mitochondria and once you produce the ATP, it actually takes work to get the ATP out. You actually have to use ATP to pump the ATP out.
Rob Pickels 47:34
Right. And that’s also why one of the primary adaptations to endurance training is to create more of these mitochondria, right. Because it can be very limiting in terms of energy production. And, you know, primarily to produce more energy this way, you need more of mitochondria, as opposed to say, making the mitochondria itself more efficient.
Trevor Connor 47:55
Yep. So going back to our battery analogy, I want to see if I can just make Rob quit for the day. Think of glycolysis as, you got this shady guy sitting outside the factory selling these tiny little batteries.
Rob Pickels 48:09
Just don’t, tell me he has a trench coat and he opens it up to reveal battery.
Trevor Connor 48:13
He does.
Rob Pickels 48:14
Yes. I think I saw that guy on Pearl Street earlier.
Trevor Connor 48:18
They’re not very good batteries. They don’t give you a lot of energy. But you can get that battery from him quick.
Rob Pickels 48:25
Yeah, you can.
Trevor Connor 48:26
Inside the factory, you got these really big, nice batteries. But you’ve got to go through a security check, you have to do all this work to get in there, you have to sign a lot of paperwork to buy the battery, and then you have to go through security again to get out before you can finally go and use your battery. So that’s kind of the difference between aerobic metabolism and anaerobic. Big batteries. Unlimited battery source, just takes a lot of work to be able to use it.
Rob Pickels 48:53
Slightly off topic. Funny story. One time I was going on to the US Army’s Environmental Research Lab onto that army base in Natick, Massachusetts. And they do a full like thorough searching of your car, like you drive over a pit with a guy like in the ground. And he’s looking underneath. And Trevor as you’re explaining to this it brought back really bad memories because I mistakingly, and you can tell this was a long time ago, I mistakingly had a disposable camera like in the door pocket of my car and I got grilled. So, people, security at some places can be real tight. Just so you know.
Trevor Connor 49:30
Did I ever tell you about my story about going to Nationals at the US Air Force Base?
Rob Pickels 49:35
No. But, yeah.
Trevor Connor 49:36
This was 2019 they had masters Nationals at the the Air Force in, right outside of, Colorado Springs. I had just moved to Colorado. So I still had my Canadian driver’s license. And the bass was on lockdown because there had been a shooting that week. I didn’t know any of this. So I show up to get to Nationals. I go to the northern security gate.
Rob Pickels 50:00
The Canadian security gate the North one.
Trevor Connor 50:02
Yeah, there you go. That’s not the way they saw it. He asked me for my ID and I get my Canadian driver’s license. Like we’re not allowing foreign nationals. And I’m like, I’m American. He goes, prove it.
Rob Pickels 50:13
Yeah. Right.
Trevor Connor 50:14
Like I’m in the middle of Colorado. Why would I bring my passport?
Rob Pickels 50:17
Yeah.
Trevor Connor 50:18
So wouldn’t let me in.
Rob Pickels 50:19
Yeah.
Trevor Connor 50:20
And I was like, rejected because I’m like, I’m gonna have to miss nationals.
Rob Pickels 50:23
That’s the worst reason to lose a race.
Trevor Connor 50:25
It was absolutely a horrible reason. So, I’m starting to drive back to Boulder. And then I have a thought there’s a southern gate. Oh, God, let’s try this differently. So I turn around. I go and park at a Safeway parking lot.
Rob Pickels 50:37
Okay.
Trevor Connor 50:37
Get kitted up, get on my bike. And I biked to the southern…
Rob Pickels 50:42
okay. And they’re just looking for people from Mexico.
Trevor Connor 50:45
Right, or Canada, just horrible Canadians. And she asked me for ID and I’m like, I didn’t know that I needed ID like my race is about to start. I just got here I came from my hotel home, I did this whole sob story. I’m like, but my race is about to start. And like I thought you’d know that nationals is going on and like, I was doing my best to look like I was gonna cry.
Rob Pickels 51:05
Oh my God.
Trevor Connor 51:06
She let me in.
Rob Pickels 51:07
Oh my god.
Trevor Connor 51:08
She let me in and I got to the race as they were like doing the announcements. So I’m like pinning up my number as they’re counting down to start.
Rob Pickels 51:18
Wow, Trevor. There’s a black SUV pulling up outside. I wonder if you’re gonna be arrested for infiltrating American naval or not Naval, Air Force Base.
Trevor Connor 51:26
That was my thought the whole race. I’m like, am I gonna get arrested by the end of this is race.
Rob Pickels 51:30
Motivation to ride fast. Anyway, back on topic.
The Krebs Cycle and the Role of NAD and FAD
Trevor Connor 51:34
Yeah. What are we talking about?
Rob Pickels 51:35
Krebs cycle.
Trevor Connor 51:36
Krebs cycle.
Rob Pickels 51:36
Or the citric acid cycle. If you want to call it that.
Trevor Connor 51:39
Or do you know the other name?
Rob Pickels 51:41
The tricarboxylic acid cycle.
Trevor Connor 51:45
There you go. Well done.
Rob Pickels 51:46
I know.
Trevor Connor 51:47
It has a lot of names.
Rob Pickels 51:48
It sure does.
Trevor Connor 51:49
It has a whole lot of names. So let’s, before we can fully explain the Krebs cycle, we need to talk about the end of glycolysis. As you said, so you break down a glucose molecule you end up with technically two pyruvate. But I agree with Dr. Sol Milan, it’s really lactate. Because pyruvate, we’re just talking about the security of the the mitochondria, pyruvate can’t cross the mitochondrial membranes. So it has to be converted to lactate, in order to go across the mitochondrial membrane. Then, once it’s inside the inner part of the mitochondria, it gets converted back to pyruvate. And pyruvate, then gets converted to acetyl-CoA. Or, I’m waiting for you to jump on for all these, oxaloacetate which I can’t pronounce.
Rob Pickels 52:39
That’s fine. You can’t pronounce any of these words, because you’re Canadian, but I’m not calling you out on it, even though I want to.
Trevor Connor 52:46
That is fair. Now, look, we’re not going to go into all these steps. You can look this up, just do a search for Krebs cycle or citric acid cycle and you’ll find all sorts of pictures of it. It’s multiple steps, but it’s a big loop because it always circles back around to oxaloacetate.
Rob Pickels 53:03
And I just want to point out as we’re talking about like, oh, well, it’s pyruvate, no it’s lactate they’re the same molecule. Lactate just technically has like hydrogen bound to it that eventually, yeah, two hydrogens that eventually basically just dissociate off anyway. So whenever we’re talking about these molecules, we’re really not talking about things that are like totally different, like a pickup verse, a passenger sedan, we’re talking about a passenger sedan that has a flag on the back of it.
Trevor Connor 53:31
Yep. But that’s actually important, where you say it’s just a pyruvate with two hydrogen ions bound to it. Because as we’re, we’ll talk about in a second with the electron transport chain, this is all about producing hydrogen ions. So it’s actually a benefit that you’re pulling hydrogen ions into the mitochondria. So that’s another role. So not only is lactate beneficial, and be able to cross that membrane, but it’s bringing two hydrogen ions in with it, which is important. And then they get released. So take a look at this cycle. It’s complex, but here’s the really interesting thing about it. This whole complex process only produces one ATP. That’s not the role of the Krebs cycle. But the Krebs cycle does and this is where finally Rob is going to jump on me, is it is reducing NAD and FAD.
Rob Pickels 54:25
Eh that works.
Trevor Connor 54:26
Damnit.
Rob Pickels 54:27
I don’t want to get into it. I want to pick my battles. This is a long episode, man. When Trevor says reducing, he’s just talking about like one chemical reaction creating another chemical reactions, we can move from one molecule to another.
Trevor Connor 54:37
Wow, thank you.
Rob Pickels 54:38
That’s simple.
Trevor Connor 54:39
So we haven’t even talked about this any NAD and FAD.
Rob Pickels 54:42
Oh God.
Trevor Connor 54:43
They are very, very important molecules here. They bind to hydrogen. So when you reduce NAD what you end up with is NADH,
Rob Pickels 54:52
correct,
Trevor Connor 54:53
plus a hydrogen ion.
Rob Pickels 54:54
Yes.
Trevor Connor 54:54
When you reduce FAD, you end up with FADH2.
Rob Pickels 54:59
Yes.
Trevor Connor 54:59
And that’s really important. They are carriers of electrons. So when we’re talking about binding that hydrogen ion or a molecule to it, what we’re really talking about is it’s now carrying the electron that comes with that hydrogen.
Rob Pickels 55:12
Yes.
Trevor Connor 55:13
So this is very, very important. We talked about how your body has to constantly be converting ADP back to ATP and then the phosphate gets released, you release energy and then becomes ADP again in that cycle.
Rob Pickels 55:27
Yes.
Trevor Connor 55:27
Yeah, the same thing with NAD and NADH and FAD and FADH2, where you have a limited supply of both of those. And you need to be constantly reducing and oxidizing them, which is binding the hydrogen to them, and then unbinding, the hydrogen.
Rob Pickels 55:43
Yes.
Trevor Connor 55:43
And that’s when you are working really hard. And all of a sudden, you feel like, hey, I’m kind of burning up here, and I can’t keep going, you’re feeling that burn, one of the big things is happening is you’re not, you’re getting a buildup of NADH. And you don’t have sufficient NAD.
Rob Pickels 56:04
Correct.
Trevor Connor 56:04
Because we didn’t talk about this. But in glycolysis, it does reduce two NAD.
Rob Pickels 56:09
And we need to make sure that we have NAD to continue that process, right. If we run out of you know, kind of think about like NAD is a bucket. And if you’re trying to dig a hole, and you got nowhere to put that dirt, you have no bucket to put that dirt in to move it away, then you got to stop digging your hole. Right. And that’s why we oftentimes talk about the inner conversion of pyruvate and lactate in glycolysis is it creates more NAD buckets, essentially.
Trevor Connor 56:39
Right. So yeah, glycolysis basically stops when you have too much NADH and not enough NAD.
Rob Pickels 56:46
And there’s some acidic sort of processes in there as well. But ultimately, that’s like the rate limiting of glycolysis. Not necessarily how quickly we can break down glucose or glycogen. It’s just this process itself can be rate limiting, because of the components that you need, the tools that you need during it.
Trevor Connor 57:05
Glycolysis produces hydrogens. And so when people talk about acid, acid at its simplest form is just hydrogen ions. You don’t want a lot of hydrogen ions floating around in your cells. So if you’re ramping up glucose and there isn’t NAD to take up those hydrogens, your cells basically say, got to stop here. Can’t have that acid buildup. And that’s again, as you said, one of the beneficial roles of lactate. Lactate can take two of those hydrogens. So it’ll take them from NADH and produce more NAD. So lactate it actually is beneficial. It’s not a waste product.
Rob Pickels 57:40
Man, Trevor, you’re getting really deep here, I think we should move on because I want to talk about alpha ketoglutarate dehydrogenase.
Trevor Connor 57:46
You’re just looking these up.
Rob Pickels 57:47
I am.
Trevor Connor 57:51
So this is the part though of the episode I was scared off, because I know that we just lost a whole bunch of people talking about NAD and FAD. But really important to understand that basically we’re about to talk about oxidative phosphorylation. And that uses electrons, and hydrogen, and NAD and FAD are the carriers. And without those carriers, everything breaks down. And so Krebs cycle, really its primary role is to bind hydrogen to NAD and FAD.
Rob Pickels 58:24
So in this whole process of utilizing glucose, and actually we’re in the Krebs cycle so we can talk about fat at this point.
Trevor Connor 58:32
Yes.
Rob Pickels 58:32
Right because fat enters the Krebs cycle as an acetyl-CoA, the whole point of trying to take these substrate molecules, fat, carbohydrate, and turn them into ATP, the Krebs cycle is just a middle sort of step in an otherwise sort of three part show.
Trevor Connor 58:51
Yep. And where glucose, I forget how many hydrogens get broken off a glucose and then pulled into oxidative phosphorylation, but it’s not a lot. But when you’re breaking down a fat molecule, depending on the size of the fat molecule, you can produce, release, basically 40 plus hydrogens. Which gives it a lot of potential to produce a lot of ATP. But for now, I think the last thing to just emphasize with the Krebs cycle is it is this huge complex process. You know, we already talked about all the difficulty of pulling in the fuel into the mitochondria, that takes work. And same thing with fat. It’s got to be transported in and then all of it gets broken down to acetyl-CoA, and then it goes through this very complex process. And you’re still producing almost no ATP. All you’re doing is binding hydrogen to NAD and FAD.
Rob Pickels 59:41
But don’t worry that ATP is coming.
Trevor Connor 59:43
It is coming. So where’s it coming? What happens next?
Rob Pickels 59:47
I don’t know. I want you to tell me.
Trevor Connor 59:49
Robby that’s so helpful this episode.
Rob Pickels 59:51
I’m here to learn. I’m not here to be helpful. I’m here to tell the people what you’re saying. So you got to say something so I can tell them what it means.
The Electron Transport Chain and Oxidative Phosphorylation
Trevor Connor 59:58
So the next process is the electron transport chain.
Rob Pickels 1:00:02
Or as you previously call it oxidative phosphorylation, because you were trying to make it sound special.
Trevor Connor 1:00:07
Right. So as I said, phosphorylation is when you bind a phosphate to ADP. And because oxygen is used, it is oxidative phosphorylation. And basically, so I also mentioned the electron transport chain. And this is where I’m going to try to explain this as simply as possible. In fact, not only am I going to keep this simple, I’m really not going to explain the electron transport chain, if you really want to understand this I mean, this would be in an exercise physiology class, several classes to explain how this whole process works. So really, all we’re going to cover here is just not how it works. But some of the things are good to understand, when somebody is talking about this, you just have some sense of what this is about, and why this is important to our physiology. So you have these complexes that are on the inner membrane of the mitochondria. So remember, there’s an outer membrane and an inner membrane, and that, in between, is this highly acidic space. And there’s a reason for that.
Rob Pickels 1:01:13
We’ll call that purgatory.
Trevor Connor 1:01:15
Yes, basically, what you’re doing is you’re taking all those hydrogen ions, and you’re dumping them into that space. Remember, hydrogen is acid. So you have this huge concentration of hydrogen ions in between these two membranes. But then what happens, so interesting thing is to produce a concentration gradient like that, where you have on one side of the membrane, a very high concentration of hydrogen ions, on the other side, you have a very low concentration, that gradient actually has energy potential.
Rob Pickels 1:01:48
So this goes back to the concept of we have to, at times, use some energy to make more energy, right. And so what we’re doing when we’re taking the hydrogens off of that NADH, that we created, because we use some energy in the Krebs cycle to make NAD plus into NADH, when we separated that hydrogen, and also the electron that goes with it, as Trevor said, off of NADH, we’re using that energy to build up you know, kind of a pool of hydrogens that when we pull the plug.
Trevor Connor 1:02:24
Right.
Rob Pickels 1:02:24
And that hydrogens begin to flow through the membrane, we can use that to do work.
Trevor Connor 1:02:30
Yep. And I love that you talked about pulling the plug, because that was exactly the analogy that McArdle used.
Rob Pickels 1:02:36
Really?
Trevor Connor 1:02:36
Think of it like a waterfall powering a turbine.
Rob Pickels 1:02:39
Yeah, exactly.
Trevor Connor 1:02:40
So you basically, that inner membrane, think of it like a dam. And these complexes, the cytochrome complexes are the actual dam that can release. So if you think of it like water, it every once in a while releases the water and that powers the turbine.
Rob Pickels 1:02:56
Yep.
Trevor Connor 1:02:56
So what happens is these complex they take the electron, and transport the electron, allow the hydrogen to come out of that inner space, that releases energy. And then that energy is used to bind a phosphate to ADP and produce your ATP.
Rob Pickels 1:03:13
Holy crap. We made an ATP finally.
Trevor Connor 1:03:17
We finally made an ATP.
Rob Pickels 1:03:18
Oh my God, we’ve been talking for an hour and 15 minutes and we’ve made an ATP people.
Trevor Connor 1:03:24
This is the point that we’re trying to make is this aerobic metabolism, produce a lot of ATP. But boy does it take a lot of work to get there.
Rob Pickels 1:03:31
Good lord.
Trevor Connor 1:03:33
And so here’s the really fascinating, so 4 of these complexes, so they can produce a fair amount of ATP. So every time that an electron gets transported, understand the electron kind of gets moved from one complex to the next.
Rob Pickels 1:03:45
It gets handed off, yeah.
Trevor Connor 1:03:46
Right, so three hydrogen ions get transported, but only one electron gets transported. At the very end of this, it’s got to do something with that electron. And this is where oxygen comes in. The oxygen takes up the electron, binds to two hydrogens, and you end up with water.
Rob Pickels 1:04:05
Yay!
Trevor Connor 1:04:06
So we talked about aerobic metabolism. But oxygen is only used in the very, very, very last step to dispose of an electron.
Rob Pickels 1:04:19
Yeah. It’s also interesting to me to you know, it’s to create water. It is interesting to me how water enters and exits at a few different places throughout metabolism. And I don’t know that people realize that it is ultimately essential to creating energy. And granted, I don’t know that we would ever end up in a point where we’re so dehydrated, that metabolism stops for that reason, but it is critical to making sure the process continues.
Trevor Connor 1:04:48
Right. And so the two end products of all those are water, h2o, which your body can then use and co2.
Rob Pickels 1:04:57
Correct.
Carbon Dioxide Removal and the Regulation of Breathing
Trevor Connor 1:04:58
And here’s the thing if co2 starts collecting, once again, this whole process backs up, you have to get rid of it to keep the process moving.
Rob Pickels 1:05:08
And it makes sense that these are the end products, right. Because we’re breaking down molecules, right. Like glucose is 6 carbons, 12 hydrogens and 6 oxygens, right. All that we’re doing is we’re starting with carbon, hydrogen, and oxygen, and that’s what we’re ending up with. They’re just ending up in different forms carbon dioxide and water. Co2 and h2o.
Trevor Connor 1:05:34
Right. But the thing I want to emphasize is the buildup of carbon dioxide, because how do you get rid of carbon dioxide?
Rob Pickels 1:05:41
Breathe harder?
Trevor Connor 1:05:42
Breathe harder. Now, you can use bicarbonate to buffer it, to a degree.
Rob Pickels 1:05:47
Well, bicarbonate is hco3. Anyway, I don’t want to go down that road.
Trevor Connor 1:05:52
Yeah, fair enough. We don’t have to go down that road. But basically, you have to get rid of that co2. So when you’re breathing hard, everybody thinks I’m breathing hard to bring in that oxygen.
Rob Pickels 1:06:03
Yeah.
Trevor Connor 1:06:03
That’s true, you need to get the oxygen so that you can keep powering this. But actually, what’s more of a rate limiter is how much co2 you can expel.
Rob Pickels 1:06:12
And oftentimes our drive for breathing is based on the amount of carbon dioxide that we have in our bloodstream. That’s what’s causing us to harp the ventilator pretty faster.
Trevor Connor 1:06:21
Yep. Exactly. All right. So here’s where I can nerd out a little bit. Because there is a complex four that gets talked about a lot. Because complex four can be leaky, meaning it just releases electrons and electrons are not used at all to produce ATP. That makes us less efficient. We’re not 100% efficient here. And you have seen one adaptation when we go to altitude, is we actually start producing a different complex four that is less leaky. So I wouldn’t say all but many more of the electrons are used to produce ATP. It’s not that you necessarily have better oxygen delivery. It’s just you’re being more efficient with the oxygen and electrons you have available to you.
Efficiency Losses and Adaptations Such as Altitude Exposure
Rob Pickels 1:07:13
Sure. You know, and for quick explanation, these complexes that Trevor are talking about, they’re little protein pods in the membrane, where these reactions are occurring. So just some different spots that are very specialized in terms of the reactions that they are helping to complete. So the details of each one, not necessarily important beyond the scope of this episode. But when he talks about complex four it is just one of those proteins that’s in the membrane.
Trevor Connor 1:07:39
So Rob, what do you think? Have we covered it?
Rob Pickels 1:07:44
I mean, yes, and no, to tell you the truth, there’s so much more information out there. We can only do so much justice to it in an episode like this. And I wish that we could be whiteboarding and diagramming and drawing funny little pool pictures and everything else. But I think that we kind of covered it in a very linear fashion from start to finish.
Trevor Connor 1:08:06
Yeah, yeah. Again, I gotta say any exercise physiologist listening to this going, oh, my God, you just butchered this or that. Yeah, absolutely. We’re just trying to give basic understanding so that when we talk about on the show, or when you hear other people talk about it, you just have a sense of what we’re talking about, it’ll actually be easier to go into all the terminology, use all the chemical names to explain this. This is one of those things, where trying to get it down to something very simple is hard to do.
Rob Pickels 1:08:37
And I want to touch on the fact that we ultimately just talked about a molecule of glucose so that we were talking about a little bit more of a simple singular process from start to finish. But as I made mention earlier, fat goes through initially a process called beta oxidation, which I can say is akin to glycolysis. It’s really not, but ultimately, it is preparing that fat molecule to enter into the Krebs cycle. And that’s where those two pathways between a carbohydrate and a fat, that’s where those two pathways converge, and ultimately are relatively the same thereafter.
Fat’s Role in Aerobic Energy Production and Key Takeaways
Trevor Connor 1:09:12
Yep. But I think if there’s just important messages to get out, those couple takeaways I have are, first of all, understand these fuels where they are source of energy. They are not directly used to power anything.
Rob Pickels 1:09:26
Correct.
Trevor Connor 1:09:27
They are only used to produce ATP.
Rob Pickels 1:09:30
Yep.
Trevor Connor 1:09:30
And then the ATP is our energy currency. It is what powers everything in our bodies.
Rob Pickels 1:09:36
That’s what powers connecting and disconnecting our muscle fibers during a contraction. That’s what powers the pumps that keep ions on the correct side of the membrane.
Trevor Connor 1:09:46
So all these metabolic processes that we’re talking about, have one purpose, just to produce ATP to take our fuels, break it down, release their energy and use that to produce ATP, and it’s not 100% efficient. It’s 34 to 40% efficient, which is pretty interesting. So the rest is lost as heat. But I think the other important message to understand here is, there are several processes here and the simple one, I’m going to skip over phosphocreatine, I think we covered that, is glycolysis. That’s our one true anaerobic process that can only use carbohydrates. It is fast, it is outside of the mitochondria. So it’s just quick, 10 steps. And then the ATP is immediately available, which doesn’t produce a lot.
Rob Pickels 1:10:35
Yeah, you know, something that I think is always worthwhile in pointing out is, it’s not like we say, oh, I’m gonna go for a two hour run or bike ride today, my body knows I’m going to do a two hour run and therefore it should use the aerobic processes, you know, we very much are turning on all of our systems right away. And we are choosing systems, ultimately by the intensity or the need to produce energy to sustain that workload. So it’s not like we have this like very intelligent forward thinking situation, when we’re out riding or running, and we got to go up a steeper hill, you know what, you’re gonna have to tap into that anaerobic energy production, to provide energy in the short term to ramp that up. Now, if you hold that new workload for a little while, then your aerobic system, it kind of has time to get itself moving up to producing more energy, and it can begin to take over more of the workload down the line. We’re always using all of these systems at all times when we say we’re doing aerobic work. It’s not like it’s only aerobic energy production that’s happening.
“Fat Burns on a Carbohydrate Flame” Explained
Trevor Connor 1:11:43
It actually, that brings up a really important point that we forgot to mention, which is there’s an expression that fat burns on a carbohydrate flame. And here’s the reason why we talked about the Krebs cycle. The first step of the Krebs cycle is that oxalic acid acid, can you please say it for me?
Rob Pickels 1:11:58
Oxaloacetate.
Trevor Connor 1:11:59
Thank you.
Rob Pickels 1:12:00
Yeah.
Trevor Connor 1:12:00
What he said. We are constantly breaking that down. So we need more. Pyruvate can be converted into ox-
Rob Pickels 1:12:09
Oxaloacetate.
Trevor Connor 1:12:10
Thank you.
Rob Pickels 1:12:12
Well, hold on. You’re saying acetyl-CoA?
Trevor Connor 1:12:13
No.
Rob Pickels 1:12:15
Well.
Trevor Connor 1:12:16
Oxaloacetate.
Rob Pickels 1:12:17
Well, oxaloacetate is the last step and then,
Trevor Connor 1:12:20
fair enough,
Rob Pickels 1:12:21
survey comes in, well, acetyl-CoA comes in…
Trevor Connor 1:12:23
It is a step before acetyl-CoA comes in. Yeah, there is no true first step. But here’s the point. So the reason I’m saying it’s the first step is it is the step before as acetoacetate, acetyl-CoA.
Rob Pickels 1:12:26
Correct. Yes. So if you want to call that the first step, it’s a round chart people the first and the last can kind of be the same. Keep going, you got it, you got it, you got it.
Trevor Connor 1:12:49
It is the first step before acetyl-CoA enters, that can be converted into acetyl-CoA, pyruvate can be converted into acetyl-CoA. Only pyruvate can be converted into oxaloacetate. So we need a steady supply of glucose going through glycolysis and providing that pyruvate to keep replenishing the oxaloacetate. Without it, the Krebs cycle is going to shut down. So you can’t run the Krebs cycle just on fat.
Rob Pickels 1:13:21
Correct. Because if you run out of or if you don’t have enough of the last step, which is then used to create the first step, then the first step never happens.
Trevor Connor 1:13:30
Right.
Rob Pickels 1:13:30
Yes.
Trevor Connor 1:13:31
We got there.
Rob Pickels 1:13:32
Eventually. In a very round about Krebs Cycle-y way.
Trevor Connor 1:13:36
So the simple explanation for that is, there is an expression, fat burns on a carbohydrate flame. If you are not keeping glycolysis running Krebs Cycle can’t run.
Rob Pickels 1:13:48
And if the Krebs cycle can’t run, then you can’t run.
Trevor Connor 1:13:51
Right. Or you can run just for like a few seconds.
Rob Pickels 1:13:55
Then you gotta lay down.
Trevor Connor 1:13:58
So the last message I just want to convey to everybody is that aerobic process inside of the mitochondria is extraordinarily complex. Not just the number of steps in the Krebs cycle, we talked about that tons of steps, it doesn’t really produce any ATP, just one, it’s just reducing NAD, then that goes into that electron transport chain. That’s an incredibly complex, slow moving process. But on top of that, there’s then these two membranes of the mitochondria and things have to be transported in things have to be transported out. That’s also very difficult. So while you can produce a ton of ATP, with this aerobic machinery, it’s just slow.
Final Analogies and Wrap-Up
Rob Pickels 1:14:41
Yeah. And you know, hey, this just popped in my head. It’s kind of like let’s say, let’s say you’re a line cook, Trevor. You do so much prep work before you ever make a meal, right. The meal, the steak that you cook is what you get paid for. That’s what earns you the ATP. But you got to get everything prepped, you got to cut your vegetables. You got to be, you know, butchering your meat and all of that. And that takes so much time. That’s like the Krebs cycle. It’s all the work you do to get ready to do the work that actually gets you paid. Bam.
Trevor Connor 1:15:13
I like the analogy.
Rob Pickels 1:15:14
Yes!
Trevor Connor 1:15:15
I like my shady guy with the overcoat, and batteries, it’s a little bit better.
Rob Pickels 1:15:23
But don’t don’t buy batteries from that guy. You know. Come on people. Just, just trust me on this one.
Trevor Connor 1:15:30
All right, shall we leave it there, Rob.
Rob Pickels 1:15:31
Let’s leave it there, Trevor.
Outro and Closing Remarks
Trevor Connor 1:15:32
I hope everybody enjoyed that. I hope we didn’t lose all of you.
Rob Pickels 1:15:37
And a final note, I want everybody to know that I never actually got to a soggy cookie. I think it totally, totally, it totally dissolved into the coffee. So I, I really I drank my cookie.
Trevor Connor 1:15:48
Did it taste good?
Rob Pickels 1:15:50
It’s hard to say. It was a little much. That was another episode of Fast Talk. Subscribe to Fast Talk wherever you prefer to find your favorite podcast. Be sure to leave us a rating and a review. The thoughts and opinions expressed on Fast Talk are those of the individual especially Trevor and his terrible, terrible analogies. As always, we love your feedback.
Trevor Connor 1:16:13
That’s even worse.
Rob Pickels 1:16:14
I know. Join- no, it’s not bad. It’s just different. And I don’t fault you for it even though I love to make fun of you because it’s just what you learned growing up, Trevor, and I can’t fault you for that.
Trevor Connor 1:16:25
That’s fair. I just love the fact that I’m a biochemists who can’t pronounce any of the chemical names at all.
Rob Pickels 1:16:31
But if, if you were in Canada, people would be like this guy is spot on.
Trevor Connor 1:16:35
Oh, thank you. So you’re saying everybody in Canada has a speech impediment?
Rob Pickels 1:16:38
Join the conversation at forums.fasttalklabs.com or tweet at us with @FastTalkLabs at thefasttalklabs.com to get access to our endurance sports knowledge base, coach continuing education, as well as our in person and remote athletes services, or Trevor Connor. I’m Rob Pickels. Thanks for listening.
