 All right. Enzymes are the magic players. Enzymes are the molecules that make this happen. And enzymes are proteins, usually. I say usually, I can't think of a single non-protein enzyme, but I hate the always never statements because I pretty much always guarantee there's an exception to something. Enzymes are, I'm just going to say, they're proteins so that we don't have to get our brains stuck on the possibility of something different. But they're proteins that catalyze chemical reactions. And when I say they catalyze chemical reactions, they help the chemical reaction occur. They don't get used up. So in our chemical equations that we end up with, like the cellular respiration and photosynthesis equations, there are a ridiculous number of enzymes that are involved in making those chemical reactions happen. Those enzymes don't get used up. The glucose in cellular respiration does get used up. It gets changed into different molecules. It gets changed into carbon dioxide and water. But the enzymes that helped make all that happen, those guys don't get used up. So they're called catalysts because they help make something happen, but they're not actually part of the reaction themselves. They're proteins, which means they're strings of amino acids that have a specific shape. The shape of the enzyme determines its function. Enzymes usually have a site, a part of them that I think of it as a sticky part. And it's called the active site. And the reactants in the chemical reaction that they are catalyzing somehow bind to that active site. So you end up with this sticky zone. And I'm gonna just all highlight the sticky zone. And just because of its shape, just because of the way that the amino acids are stuck together, it's like a magnet. Here's another reason for me to have magnets to play with at my desk because a substrate will bind to that active site. And then the binding causes a shape change in the enzyme itself. So this is a phenomenon that we'll see over and over and over that proteins bind to molecules. And when they do, they change shape. In the case of an enzyme, that shape change isn't permanent, but it does impact the substrate. So you can see that the substrate started out as a green molecule with that shape. And after the enzyme did its thing, had its shape change, the molecule comes out different. So the molecule was changed. And then the enzyme goes back to normal. That says normal and it can be used again. Over and over and over, it can be used over and over. As long as you have substrate, you're gonna continue to produce those products. Lots, we're just gonna see them all over the place. How, how do they do, or how does that speed up a chemical reaction? Well, the way that this works is through a process, they basically decrease enzymes, decrease activation energy. And I have this little visual here of the activation energy. Let's make it blue. Here's the activation energy. And this is saying there's no enzyme here. So without an enzyme, we have this much energy. And it's the barrier that is, we have to break some chemical bonds in order to make this chemical reaction take place. We have to put energy in. The size of the activation energy will tell you how likely it is for the reaction to take place. Well, an enzyme is gonna come in and decrease the energy, the activation energy. And look, you can see that the activation energy in the second time with the enzyme is much smaller, which means that the chemical reaction is more likely to happen. I'm done. I don't need to tell you anything else about enzymes or how, we're gonna talk about cellular respiration next and then we're gonna talk about photosynthesis and I'm gonna show you all the enzymes that are involved. There are a couple of them whose names we'll remember. We'll remember your name, little enzyme. Thank you, thank you. But most of them, we're gonna be like, we know you're there doing the work, the thankless work. We're glad that you aren't disappearing, but we're not gonna remember your names because there's way too many of you. Facilitating just those really what we would say, like what, those are pretty simple, don't they seem simple chemical reactions? I don't know, maybe that isn't simple to you, but once you memorize it, it's like, dude, there's just a few things involved. Enzymes are where the butter is buttered, whatever, nobody knows what that just meant. I think I do wanna say one more thing to you about enzymes, you can break them. I'm just gonna write that down right here. You can break an enzyme if you denature. If you denature the enzyme, and I can't remember if we talked about denaturing proteins or not already, but there are two things that can cause a protein to become denatured. Denatured proteins don't go back to their original shape. So a denatured protein is a shape change that is irreversible. Do we wanna guess? Think about buttermilk and vinegar, adding those together. And think about frying an egg. If you change the pH of the arena around a protein, you will change its shape forever, which is why living systems maintain pH in a very narrow range, because our enzymes, our important proteins will change their shape if the pH around them changes and temperature changes and can permanently denature a protein, change the shape of a protein. An egg cooking in the frying pan is a perfect example. The heat from the frying pan denatures the proteins in the egg and changes how they look. Egg white was clear and slimy and it turns white and not slimy. Rubbery, it turns white and rubbery because the heat denatured those proteins. Okay, go denature some proteins to have your dinner and provide yourself with fuel because when we come back for the next lecture, we're gonna hammer home cellular respiration and photosynthesis. Holla, doggies.