[BLANK_AUDIO]. Welcome to week three of Vital Signs. This week, we're actually not going to be learning about a vital sign. We're going to be learning about metabolism. And the reason that we're taking a break from vital signs to think about something like body metabolism is the fact that metabolism underlies what's going on with body temperature regulation and respiration rate. So we can't really get into studying and thinking about and learning about respiration rate and body temperature until we have some key concepts about metabolism under our belt. So today we're talking about metabolism. We'll have a demonstration were you can actually see some changes in a subject's body metabolism. And then hopefully this will give you an understanding for what's going to come up in subsequent weeks when we look at body temperature and respiration rate. So I know that metabolism is one of your favorite topics. >> [LAUGH]. >> And typically I know that. Metabolism is a difficult concept because it involves lots of chemical reactions and chemistry is not something that all of us know a lot about or seem to care a lot about. But we have to talk about some of the generic reactions and pathways that underline metabolism, just so we can understand how fuels are being used in the body and what's really happening when your cells are doing their work. So when I use the term metabolism, what do you think about? Lauren. >> The combination of chemical reactions in the body? >> Yes, so when we say, when we talk about your body's metabolic rate, we're talking about the total activity that's happening metabolically in all of the cells of your body, right? And if we had to think about what kinds of activities are happening metabolically, what would they be? Yes, Steph. >> Well, your body burns fat and uses it for different purposes. >> Okay, so it burns fat and that idea of burning fats is really a kind of generic category of chemical reaction that we call catabolism, right, or a decomposition reaction. We start with a bigger molecule and we break it down in to a smaller molecule. And there are lots of decomposition reactions that go on in your body all the time, right? And we'll get back to that in a minute. But what else? Mia? >> Along with the breaking down there's also building up reactions. >> Building up, and what's the name we call breaking down catabolism. If it's building up? >> Anab. >> Anabolism. >> Anabolism. >> Anabolism. So we have catabolic reactions, which are the breaking down, and then we have the anabolic reactions, where are the building. We take smaller substrates we call them, just smaller building blocks, and we put those substrates together to make bigger molecules. That's an anabolic reaction, right? So, if we think about Lauren's definition of metabolism, then we can, we can say that your body's metabolism is made up of catabolism and anabolism. And the sum total of all of those chemical reactions is your body's metabolic rate. Right? That's easy, right? Okay, now I want to get back to Steph's idea of burning fats. Fats are one type of macronutrient. Okay, when we use that term macronutrient we're talking about the big organic molecules that we use to fuel the work that takes place in the body. So fats are one of those molecules. What are the other two macronutrients? Lauren. >> Carbohydrates and proteins. >> Excellent. Carbohydrates and proteins. So now let's think about those three macronutrients and think about them in the context of catabolism and anabolism. Okay? So we eat a diet that contains those macronutrients. And it's a job of the digestive system to digest those macronutrients into smaller building blocks, right. And, and we have to digest those macronutrients, because molecularly they are too big to absorb across the wall of the digestive tract. So we have to break them down into smaller molecules so that we can absorb them, right? So when we take in carbohydrates, they would be sugars or starches. Your digestive system will break them down into simple sugars, right? And we absorb them. Okay. If we eat proteins in our diet, the digestive system breaks them down into their small building blocks. What are they? >> Amino acids. >> Exactly. Amino acids. So, we eat proteins. But what we really absorb is amino acids. And then we have, what's left? Lipids, lipids, what happens to them in the digestive tract? We break them down, in to, you have an idea, Mia? >> Glycerol, and fatty acids? >> Monoglycerol and fatty acids, which we can then absorb. A weird little thing happens in the, in the wall of the digestive tract. The epithelial cells actually put the monoglycerides and fatty acids back together into a triglyceride molecule so that we then absorb it into the, into the body as a triglyceride, right? That's a strange little thing. But so, that's catabolism. And really, chemical digestion of the foods we eat is a catabolic reaction, and it enables us to break down big macronutrients so we can get them into the body. Now, after the nutrients get into the body, you know, eventually, by one route or another, we'll get them in the blood, right? And the nutrients float around through the body in the blood and as they're floating around, we think of them as being part of nutrient pool, right? So the cells of your body, could take up the nutrients that they need out of the nutrient pool and use them, right? And during digestion what happens is we digest and then absorb new nutrients into the nutrient pool. Right? So, do any of you go to swimming pools? Ever? Or do you go to the beach on a crowded weekend in a, on a hot summer day? You know how crowded the water is when it's really hot outside? Yeah that's what happens in our blood when we're absorbing nutrients, right? The nutrient pool fills up and then, you know, we don't eat for a few hours, the nutrient pool starts to empty as cells pick up nutrients and use them to fuel their metabolism. That's pretty cool, I think. Okay, so that's anabolism and catabolism. And we've got this nutrient pool and cells pick up and use nutrients in the nutrient pool. Let's think about, if cells picked up amino acids, what would they tend to use them for? Why do cells need amino acids? Mia, do you have an idea? >> Amino acids can be used to build muscles. >> Exactly. Muscle cells need to build proteins. Right? And so muscle cells could pick up amino acids out of the nutrient pool and use them to build new proteins. Right? What else Lauren? >> Can't they also be used to make like strands of DNA and RNA? >> Depending on the nutrient. Now, DNA and RNA need a special kind of substrate, called a nucleotide, which we're not talking about today. But yes, that, that would definitely be something going on in the nutrient pool too. What else? So what other things are in the nutrient pool? Simple sugars are in there. Cells are going to pick up simple sugars. What are they going to do with them? >> Do they use them to make energy? >> Yes. Now, what does that mean, they use them to make energy? >> Maybe to like perform whatever function that the cell has. >> Yeah, so does your cell just like say, oh, I have to do some function and so I'm going to use sugars to do it? What's your cell have to do with the simple sugars? >> The simple sugars combine with other things and at the end of this cycle, ATP comes out,. >> Okay, so yes, so that's, that's, that's kind of what happens. So this is where decomposition reactions have to occur. Right? So your cells need energy so they can do their work. Right? Maybe their work is building proteins. So they, the cells might have to take up amino acids so they can build proteins. But they'd also need energy to build bigger molecules, right? And so they might also be picking up energy so they can build bigger molecules. But the thing is, we can't use simple sugars. We can't use carbohydrates directly to perform anabolism in the cell. We can't use carbohydrates directly to do any kind of cell work, but we can use the energy in carbohydrates to create ATP right? So there's a generic term that we use to describe that ability to take carbohydrates and convert them or yeah, convert them and break them down to produce ATP. Does anybody know that term? >> Glycolosis? >> Well, that's one stage of this big long process. >> Cellular respiration? >> Exactly. So cellular respiration is what's going on in the cells that allows them to take a macronutrient and convert it into ATP, right? And ATP is important, why? Because that's, we think of it, if you have to give things a really broad name, you'd say ATP is the energy currency of the cell. And what it, what me mean by that term, energy currency, is that your cells can use ATP to do work. Okay? They can't use simple sugars directly to do work. They can't use proteins or amino acids directly. They can't use lipids directly, but they can convert any one of those macronutrients to ATP by way of cellular respiration. [BLANK_AUDIO]
