Biology: Bioenergetics: The Laws of Thermodynamics

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I've got something really cool I want to so you that is going directly relate to what I have to tell you about when we start talking about enzymes and energy. But first, let's take a look at this. Now, I'm going to take this marble and I'm going to put it in here and I want you to remember a couple of terms I'm about to use. I'm going to do some work on this marble. Now, it's not going to exhaust me. I'm probably not going to break out in a sweat, but I'm going to take this marble, I'm going to pick it up and I'm moving it into this hole right here. So now this marble has lots of potential energy. See, that was a good demonstration of potential energy. Now let's see if I can get it go the other way.
So, here we go. Yep, I'm good at this stuff. There you go. Did you see that marble do work? Let's get rid of this thing here first and then we'll talk about enzymes. What did this have to do with energy? Well, you saw that the marble did work. What did it have to do with Biochemistry. There wasn't much Biology there, was there? Well, you know, if you think about what I've been trying to tell you. That Biology is literally the result of forces, both atomic and physical, that occur within our bodies and within our environment. Then this had everything to do with Biology. You see, Biology is about energy.
Let's talk a little bit about energy. In fact, let's start out this whole discussion of enzymes, believe it or not, with some physics. Let's talk about the laws of thermodynamics. There are two basic laws that rule all reactions on this planet. Everything, all forces are ruled by these two laws. The laws are very simple. Laws you probably learned in elementary school. One, energy can neither be created nor destroyed, but it can be transferred. I defy you to go out and create some energy. Did I create energy when I picked that marble up? Absolutely not. Did that marble create energy when it hit that spoon and flipped it up? Absolutely not. But energy was transferred. Energy was transferred from me to the marble, from the marble, to the spoon. Energy transfer.
So, energy can be transferred, but it can't be created or destroyed. Okay, so now that we know that energy can be transferred we come to another very important aspect of the laws of thermodynamics. Energy transfer increases entropy. Now, you're probably saying, "Yeah, so what does that mean?" Well, let's talk about entropy. Entropy's tough. Entropy wears us down. Entropy--well, let's see. So, energy transfer increases entropy. Entropy is a term we use for the tendency toward disorder. Now, if you ever saw my classroom, you would know what entropy meant. My lab is a lab on entropy. I just can't keep that thing ordered. It's constantly going toward disorder and that's a great analogy for what happens when we actually do energetic. Things tend toward disorder. In fact, and here is the true secret to life, life is the battle against entropy.
You see things are constantly going toward disorder. Things are going from organized to disorganized and energy is going and life is constantly pulling energy together, putting it together in some kind of non-entropic way. A word I made up. But the bottom line is it's definitely putting that together so that it can battle and keep things organized. Yet, life, pulling that together is always battling against that tendency. Now, we're going to talk about energy and the aspects of this thing that showed that. I want to talk to you about a concept called, "free energy". No, it doesn't mean it's free. There's an old saying, "There's no free energy."
So, you know what? That whole idea of free energy, though, starts to work within biological systems. Free energy is defined as the energy available to do work. It's the energy available to do work. We can mathematize this and sometimes mathematics can be very helpful, because it can just make so black and white a concept. Let's take this concept of free energy and take a look and put it in this context of entropy. I'm going to use some abbreviations here that you'll probably see in many, many Biology books.
Free energy we're going to call G. Free energy--and let's again, mathematize this. If you think about it, it's going to equal something and here's what it's going to equal. It's going to equal the total energy of the system--of any given system, the total energy minus something. Well, minus what? Well, minus entropy. We're going to call entropy S. Now, you notice I'm leaving a blank here, because I'm going to throw something else at you in a second. But here's the thing. If you take a look at this--if there is a tendency toward disorder, which there always is, and you have a certain system or a certain situation, take the total energy, take way its entropy and you have the energy available--that's not going to be swoosh, entropied toward disorder, that's used for work. But I have to add one thing to this. Because you see, molecules, all things tend to get more chaotic when you heat them up, when they're warmer.
You know that, it's a simple fact. When you warm water up, the molecules move faster and faster and faster and faster and there's more tendency toward disorder. Well, we have to add T in here and T is going to be a factor that we're going to put in there. So, the total free energy or the free energy available is the total minus the temperature of the system times its tendency toward entropy. Okay, that's just making it mathematical, so that it can make sense
Well, what was this all about? What was this thing with the rolling ball and the spoon and everything else? That was about free energy. Let's use that as an example. When that ball was at the top of the ramp--so we started and that ball was up on top of that ramp, like so. That ball had an enormous amount of total energy. But think about it. When the ball was up there it was kind of unstable. Now this whole concept of stability is going to be very important to you. The more--since I put energy into that it became unstable. You know that ball, as it sits right here, is pretty stable. There's not much chance of a ball on the ground of falling.
Now we were talking about gravitational energy, when I had it up there. That's gravitational energy and you're going to see, with molecules, we're going be dealing with a little bit of a different analogy, but nevertheless, I put gravitational energy in there and there was instability in there. So, there's a point there and the point is this. If the more you organize things, the more you put them together, the more free energy their going to have. So, this ball, right now, if I were to put it on this spoon, it's not going to have the ability to do anything to that spoon. I had to drop it on that spoon and make that spoon move. I could never do that again, if I tried. So, I'm going to put that spoon right there.
So, this ball up here had a high amount of energy, the ability to do work, but it was unstable. That's what it's all about, instability. Now, let's move on. Let's look at another analogy. Take a look at molecules, because that's what this is suppose to be all about, molecules. Let's take a look and make believe that this a membrane and we have a high concentration of molecules on this side of the membrane and a low concentration of molecules on this side of the membrane. Well, what we have here in this very organized situation, is a situation where energy can be out put. So, we've organized things and then the organization of those things we have added energy. We've concentrated those things right here. So, we have instability and yet when we go down to here, it's like that ball rolling down. Now, it's gone downhill. You see. And since it's gone downhill the energy has, in essence, dissipated. There's less energy involved.
Here's another example. Let's take a molecule. Let's make believe this is glucose. See the analogy? Because you use glucose for energy. Glucose is highly organized, but--and it's not as stable as these molecules here, which could be water and carbon dioxide. So, what we've done is by putting his thing into an organizational situation, we have increase the free energy in it and therefore given the ability to give free energy off. Let's go one more time and mathematize this a little bit more. So, we want to harvest free energy. That's kind of what this is all about. That's what life is all about, harvesting free energy. Therefore, we need to have changes in free energy.
I want to work with this G concept one more time. Now, this G concept is going to look something like this. Let's talk about the changes in free energy. Not just free energy, but change, because that's what we care about. So, I'm going to put a triangle here and we're going to call it delta G. Change in free energy is going to be equal to the final state of the free energy. In other words, how much is left at the end. Of course we have to take away the starting state, G initial. How much did we start with? How much did we end with? And that's our change.
Watch this. Let's take a reaction where we're going to start out with a large amount. So, let's just say--I'm going to make up units here, wolf units. Two hundred wolf units of energy and let's just say, when we're done we're down to one hundred. Well, one hundred take away two hundred, delta G, the change in free energy is going to be negative one hundred. That is a reaction that gives off energy. So, when delta G is negative, you've given off energy. Therefore since it's negative, we are going to call that an exergonic reaction. Ex, given off, exergonic reaction. On the other hand--one other thing. This is something that happens in a process called catabolism. Have you ever heard of metabolism? Metabolism is your body processes and there are two different kinds. There's catabolism, which gives off energy, such as exergonic, which tends to break things down and then there's the opposite.
Let's talk about that in terms of delta G. Well, once again, delta G--show you the equation. Delta G equals G[f], the final free energy minus G[i] the initial free energy. Now let's take a situation and plug numbers in. Let's say our final is two hundred and our initial is one hundred. Well, think of a logic here. We have more in at the end than we do at the beginning. We've input energy. Since we've input energy we've made it more organized and delta G is positive. That is an endergonic reaction. You might know that as synthesis. Right? Because you can put stuff together and you know that's the thing. This is called anabolism.
I've just got to tell you--where do enzymes come in here? Well, here's the thing. Life is a constant struggle to balance these two things and we use a process called energy coupling and here's the scoop. In energy coupling what we do is we use a catabolic reaction. Catabolism, in other words an exergonic reaction, to run synthesis endergonic reactions. So, in other words, we use something like synthesis. To do something like synthesis, we use something like respiration. To get energy--we need to get that energy and to get that energy we have to burn something and to burn something, we use that energy to make something. Life is truly wonderful. Wait until you see enzymes.
Inorganic and Organic Chemistry
Enzymes
Bioenergetics: The Laws of Thermodynamics Page [1 of 3]