Transcription
So how do, how does life exist on Earth in the universe when it seems to go against the second law of thermodynamics? Well, here's a little scenario for you. Um, on this diagram, I have a, a marble or a little ball sitting in the bottom of a dip here, and I, this ball is very stable. It's not going to go anywhere. It's, uh, not very complicated. It's stable where it's sitting. It's also very low energy.
Now, for life, I need things to be very complicated and organized, which means they have a lot of energy stored in them. Uh, so I need to get this ball to be more complicated, and I need to get it up this hill. That's the same as like building, that could be equated to building skin, building hair, building muscles, like making something big and complicated from simple starting blocks. That's what life is all about, building complexity. Um, so how do I make this, how do I get this ball up the hill? All right. Well, I could push it. I need to put energy into it, right, to get it up that b, up that hill.
Well, here's an, here's a suggestion. What if I had a second ball that was up here? All right. What could I do to the second ball to try and get the first ball up the hill? Well, let's, uh, go to the next slide here real quick. Um, what I can do is, and I don't think my animation is going to work, but if I were to push this second ball down the hill, that would go really easily. It wouldn't take any effort. It would just roll on its own. It would hit this one, bam, and it would push this one up a little bit. All right. So I would be able to get ball number one up the hill a little way by rolling ball number two down the hill and transferring the energy from ball number two as it hit ball number one into ball number one and propelling it up. All right.
Now, that's using a ball, an example of balls rolling on hills. But if you take the balls away and don't think that this is a dip and two hills, and instead, if I was to draw axes, like make this like a graph, what does this graph look like right here? A downward slope graph. That should look like an exergonic or an energy-out reaction to you. And if I was to draw, um, axes on this side, that's not very straight, uh, this should look like an endergonic curve, an energy-in reaction curve. Right.
So what we're really trying to do here, if we think about it in terms of energy instead of balls on hills, this is an endergonic reaction where we're trying to build something big and complicated, and it takes energy to do it. This is an exergonic reaction, which is an energy-out reaction where energy is released. And if we can get these two things to happen together, the energy that comes out of the exergonic reaction can be picked up by the endergonic reaction to make the endergonic reaction happen. The energy that pushes the endergonic side is the energy that came out of the exergonic side. And this is something that we call coupled reactions. They're coupled, they're joined together because this one won't happen unless this one happens first. All right.
And this is the solution to how we create order in our bodies. Our bodies, to create all the order that we have, have to do countless thousands of endergonic reactions every day. We're constantly building stuff. We're putting together skin and hair and muscle and cells and membranes and DNA and proteins, and we're building stuff day in, day in, day in to keep ourselves alive and functioning. But every single, and there's millions of different things we do, these endergonic reactions, this could stand for any one of thousands of different things that we need to do on a daily basis to stay alive, to build ourselves. Um, however, every single one of these endergonic reactions needs a push. Won't go unless there's energy to push it. And the energy comes from an exergonic reaction.
And what's really cool in our bodies is that it's like there's one exergonic, a one-size-fits-all exergonic reaction that we use over and over and over again in our bodies to drive all the different endergonic reactions that we need to do. So this curve could be multiple things. There's many different reactants and products. This could be on the right. But on the left, there's one go-to reaction that we use in our bodies a bajillion times a day that releases energy that is used to power all the other stuff we need to get done.
So what is this magical ex, exergonic reaction that we do in our bodies that we use to drive our endergonic processes? Well, it has to do with ATP. So you may be familiar with this molecule, uh, already. It stands for adenosine triphosphate. Um, and its structure is like this. This, this part here is called adenosine, the adenine and the ribose stuck together. And then it has, that bit's not super important right now. What's important is this TP part. The T stands for tri, like three, and the P stands for phosphate, triphosphate. So here and here are the three phosphates, one, two, three, in a chain kind of hanging off the side of the molecule. So this is a cartoon of ATP showing the adenosine part in blue and yellow, and then the triphosphates. Here's a more scientific-looking picture of it, space-filling model. Here's the adenosine part, here's the three phosphates, one, two, three. All right.
So what exactly is so special about adenosine triphosphate? All right. Well, what's super cool about adenosine triphosphate is that you are able to take adenosine triphosphate and snap or break the last P from the triphosphates off the chain. So you go from being adenosine with three phosphates stuck in a line. If you break off the last one and let it go, you only have two left, and that is called adenosine diphosphate. And then here's the third, the one that fell off, right? So ATP can be broken down to make ADP plus P. And when that last P gets broken off or comes off, energy is released. And that's our exergonic, our one-size-fits-all exergonic reaction that powers every single endergonic reaction that our body does.
Now, there is a really cool process by which we recycle ATP and we stick the P back on, and we'll get to that in, uh, two weeks. But for now, I just want you to focus on the energy-out part here, where you take ATP. Um, so I'm going to go back to this picture. Take ATP, break off that last P, and then you end up with ADP, only two phosphates, and a P stuck, and a P separate, number three. All right.
So if I was to go all the way back to this slide here, you remember this one? All right. We said that this endergonic reaction could be building lots of different things, building hair, building skin, building muscles, building glycogen, building proteins, because all that takes energy. But the energy to do that comes from one reaction. And the one reaction is taking ATP and breaking it down into ADP plus P. And the energy that comes out is then used to drive that second ball up the hill. So our exergonic breakdown of ATP is coupled to whatever endergonic reaction you need to get done to make it happen in your body. And that is how we are able to create order out of chaos, because we're constantly breaking down ATP to release the energy that allows us to push lots of balls up lots of different hills. Um, and we can do that for so long, but eventually we're going to lose that battle. Like we said, eventually this order will take over, and you will end up losing the battle.