 Okay, let's do this last reaction coordinate. This will be a one-step reaction, so A to B. So, of course, this is the rate-determining step, right? There's a transition state there, so let's just draw that. And this isn't something that you haven't seen before. But we're going to put in a new kind of twist. Okay, there's these things called, so let's write everything. Transition state is up there. Okay, so let's throw in a catalyst. Okay, so what is a catalyst? A catalyst is a substance that increases the reaction rate by lowering the activation energy. Why? Because, so why does it increase the reaction rate? Because the activation energy, this is what takes so long for the reaction to occur. Okay, so if you lower that pump, right, it makes the reaction go faster. Okay, so what it does is it makes a catalyst reactant complex. Okay, so I'm going to erase this portion so we can get more detail on here. So it'll be like now a two-step reaction. So instead of going from A directly from A to B, it's going to go from A to an A catalyst complex. And then back to B, like that. And then, so now we've got a TS1 and a TS2, like that. So it's now become a two-step reaction. But it's lowered the activation energy. So it's more like, I'll actually write something. So, here now we've got TS1, TS2. This is the A catalyst complex. And here is the lower activation energy, the A1. Notice that's much lower than that, right? And if I ask you which one of these two is the rate determining step, the first step or the second step of the catalyst, what would you say? The first step. The first step, so what you would compare is the rate determining step of this one to the rate determining step of this one, right? And you say which one's bigger and which one's smaller, right? This one's much smaller, so this reaction went faster. So when somebody says, you know, I put a catalyst in my reaction, that means they are, you're the catalyst for something to happen. It means that you lowered the activation energy, you know, and made the reaction happen easy. So what a catalyst does is it takes the two reactants and instead of making them find each other, because reactants are, it's like trying to play freeze-tack. But they're blind molecules. It's like blind people trying to, they're blind molecules trying to play freeze-tack. It's going to take a long time. What a catalyst will do, it's like a seeing eye dog. It will take the molecules and walk them to each other. So it grabs the two molecules, puts them in close proximity together, and reacts them together, okay? So it's just a molecule that has a structure that can grab these two molecules, other molecules, and react them together, okay? Things like enzymes are very good catalysts, okay? If you look at enzymes, read about enzymes, you know, things like that. Those are bio-catalysts, okay? Of course, there are other types of catalysts like palladium catalysts. A lot of these metal catalysts will produce hydrogen gas or, you know, help crack, you know, these hydrocarbons to make fuels and things like that. So there's a lot of, you know, uses for catalysts, so whatever, okay?