Transcription
Hi everyone. Uh, so today we are going to be talking about different types of large biological molecules, mainly carbs and fats. And, um, I wanted to pose this question to you, which is, um, why do we eat? Why do animals eat? Humans eat, right? You know, what do we eat? Well, two main reasons. So see if you can think to yourself what the two main reasons are for why we, on a purely physiological basis. Nothing. I mean, there's many psychological reasons why we eat because bacon is delicious and chocolate is delicious. But on a simple physiological level, there's two main reasons why we eat.
The first reason why we eat is to get energy, or calories, from our food to power all the movement and action that we need to do to survive. So we do eat for energy. That's one thing, and we'll be diving more into that in unit three.
The other reason why we eat is that we need raw materials to build, repair, and maintain our bodies with, right? So at one point, when you were born, how much did you weigh? Hopefully, for your mother's sake, somewhere between six, seven pounds, right? So at some point, you weighed six, seven pounds. Uh, fast forward 18, 20, 30 years, and here you are today, and you, I don't know, maybe weigh 150 pounds. So somehow you went from weighing six pounds to 150 pounds. So where did that 142 pounds of you come from? As you walk through the air, did it stick to you and build you up? No, it didn't come from that. The actual stuff that you are made of, your flesh and bone and skin and hair, all that stuff came from the food that you put into your body. And we built our mass, our our flesh, and everything from the food that we eat.
So, and even if you're not growing size-wise anymore, like you did when you matured, you still have to eat on a regular basis, and that's for maintaining and repairing, uh, your your body. So like, if you cut yourself, you have to grow new skin over to seal back up again. You're growing, you're making more skin. Um, and you need to, so that's repairing. And you also need to maintain, you know, as we walk around, like it or not, we're all shedding pieces of skin just off of ourselves as we walk around. It's kind of gross. And so we have to replace those skin cells. So repair, growth, and maintenance. All right.
So, delicious pizza we have right here. Um, pizza is a good example here because it contains carbs in the crust, and it contains fat in the cheese and the pepperoni, and it contains protein in the pepperoni and cheese as well. The four, the three main biological molecules: carbs, proteins, fats, in this one food. The perfect food stuff. All right.
So, um, we can see the pizza as it looks to us, um, on the left. But if you were looking at this purely from a scientific, biological, chemical way, you would see this piece of pizza simply as a collection of large molecules. And that's what this strange diagram here on the side is supposed to show. It's supposed to show that we're using these solid black lines right here to represent covalent bonds that are linking together a big molecule. So while this looks like pepperoni and crust and cheese, really, if you delve into it at a molecular level, it's carbohydrate molecules and protein molecules and fat molecules all mixed together. So throughout this class, this whole semester, you're going to start start getting used to thinking of the world as a collection of molecules that interact, all right, and explaining things at the level of those molecules rather than a big circle of pepperoni. All right.
So, let's, um, take this, this piece. So we're going to say this diagram, this thing here, represents one of these big molecules in this pepperoni. We'll say it's the carbs, the starch from the bread and the dough of the pizza. All right. So here is the, uh, carbs, the starch from the dough. We take it into our mouths and we chew it up. That doesn't really break down the molecule. It breaks the dough into smaller pieces of dough in our mouths, but the molecules are even tinier than that. So we're not really breaking down molecules when we're chewing. We're just separating the big chunks into smaller chunks of bread, basically. Um, but excuse me, let me erase that. Um, when you swallow that chewed-up food into your stomach, you are able to chemically do a chemical reaction and disassemble this giant molecule into these smaller parts. And this is what we would call digestion, right? So it happens in your stomach and in your small intestines. We're disassembling the molecules from the pizza. Now, this could be the carbs breaking down into smaller carbs, or this could represent the protein in the pepperoni breaking down into the smaller parts of proteins, which is called amino acids. We'll get to that later. Or this could even be the fat molecule breaking down into smaller components. So it doesn't matter which molecule this represents. The idea is the same. You eat it as a giant molecule when you eat it, and we break it down into smaller pieces, into smaller molecules. Then we take those smaller pieces and we transport them throughout our body and we reassemble them into a new molecule. This molecule is made of the same building blocks, the same blue rectangles, as this one was, but it's different. Can you see how it's like arranged slightly differently? The layout is different. We have rearranged the subunits. Um, so basically, you ate pepperoni. I'm going to call this pepperoni. You digested it into its constituent parts, and then you rearrange them into bicep muscle. Pepperoni is full of protein, so is bicep muscle built of the same thing? But if you were to look at your bicep, it wouldn't look like pepperoni. And that's because it's actually put together different to pepperoni, right? So it's made of the same building blocks, but put together in a different arrangement. Again, you can think of this like, uh, the Lego analogy. This is a race car made of Legos. We're going to break it down into the individual Legos. Here they are. And we can use those same Legos and instead of building a race car, we can build a castle. So we've gone from race car to castle using the same pieces. We've gone from pepperoni or cheese to human bicep using the same pieces. So we're going to dig in more into this idea as we go. But, um, you could rearrange these pieces into this shape, or you could build them into this shape. Whatever your body needs is what it's going to build. So you're going to eat the pepperoni. It always looks like pepperoni. But when it's broken down into the individual pieces, it could be built into bicep if you need a bicep, or it could be built into skin if you needed skin, or it could be built into nails or hair, or even insulin or some other molecule that your body needed. Um, so this is what I mean by you need to eat for raw materials, for building blocks, to build all the things that your body needs to survive. And your body doesn't look like pepperoni or cheese or dough, but it was built from the same building blocks that pepperoni, cheese, and dough are made of. That's where it gets a little crazy.
So, one last piece is that we can also take these individual building blocks and we can break them down even further. That's what these two arrows are showing, into these really tiny pieces. And when you do that, it's kind of like melting down the Legos to their real basic plastic, what it's made of. When you do that, you release energy. And that's how energy comes from our food. So this, this diagram basically shows both aspects here of why we eat: for growth, repair, and maintenance, that's this side of it, and for energy, and that's this side of it. And we are going to really dig into how we get energy from our food, but that won't happen until unit three. For units one and two, we're going to be focusing on the right side of this, this diagram, and this idea about breaking down and building up molecules from building blocks. All right. So I think that is it.