Hi. In this video, we're going to be talking about enzymes. So, enzymes are really crucial in cell biology, and a lot of biology, and they have super important functions, so we're going to spend a lot of time talking about what enzymes are, what they do, and how they work. So, first, what are enzymes? Well, enzymes can be protein or RNA, that essentially, their purpose is to reduce the energy necessary for a chemical reaction to occur. So, enzymes act on what's known as a substrate, which is just the molecule that an enzyme acts on, and it's highly specific. So, enzymes don't just go around speeding up reactions of anything. They are really specific to a single molecule or really just a couple of molecules that are very similar.
So, they act very similarly. And they also catalyze. That is another term that you are going to hear a lot about with enzymes. What that means is that they speed up the rate of, or increase the rate of a chemical reaction that the substrate needs to undergo. And so, they can actually speed up reactions, making them very fast. So, the number that's mentioned in the textbook is going to be 108 to 1013 times faster. So, what does that actually mean? Well, for a reaction that would take 3 to 300,000 years to happen by itself, an enzyme can actually make it happen in one single second. So, they really speed up chemical reactions, which you can imagine is very important because we can't wait around 300,000 years for a single chemical reaction to occur. We need them to happen now, and usually, we need them to happen repeatedly over the course of a lifetime.
So, we really need enzymes to speed up reactions. Now, they can work to speed up forward or reverse reactions, but essentially, for an enzyme to be considered an enzyme, it must meet three conditions. The first is that the enzyme cannot be consumed in the reaction. So, once the reaction takes place, the enzyme still needs to be present. They cannot be changed by the reaction, meaning that the enzyme stays the same before the reaction as it is after the reaction, so that it can be used again. It can't be used up, and it has to stay the same. And, the enzyme only affects the rate of the reaction and does not affect the free energy. So the free energy of the reaction stays the same. All the enzyme does is come in and make it happen faster.
So, if we are looking at an enzyme, here we can see this is the enzyme. And these here are substrates. And so the enzyme binds to the substrate and catalyzes some type of chemical reaction that the substrate needs to undergo. It speeds up that chemical reaction. So now, let's move on.