Practice - Bioenergetics 1 - Video Tutorials & Practice Problems
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Practice - Bioenergetics 1
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If you haven't yet tried question 8, pause the video now and give it a shot. The 5 major features of signal transducing systems are specificity, amplification, modularity, adaption, and lastly integration. Now, the question asks for just these names but let's talk about what each one means again. So, specificity is specificity like we've seen with all the proteins we've looked at up to this point. You know, these proteins have specific interactions, and the signals that they're using are generally chemical in nature. Amplification. Remember like, with our example of epinephrine. One molecule of epinephrine binding to a receptor can lead to a 100,000 molecules of glucose, right? So that signal can get super amplified and it gets amplified basically each step of the way on the signal pathway. Modularity. Proteins, are able to interact with multiple components of the pathway, right? They can interact with a, the signal and also then interact with the receptor, Adoption. Right? These, these signal pathways are able to attenuate their response, right? So you'll have some sort of, feedback from the signaling pathway that for example, will remove, and then, you know, using the example of epinephrine again, you know, where we'll, have feedback that will actually remove epinephrine receptors from the membrane to attenuate that cell's response to the ligandepinephrine. So, these signaling pathways adapt, right? That's, that's the important feature. And then lastly integration. Remember that figure with all the different systems coming and intersecting? Remember talking about crosstalk. There's so many different signal pathways that are all going on all at the same time and those signals have to integrate together so that the cell comes up with the appropriate responses. Now, let's flip our attention over to bioenergetics. So, taking a look at question 9, if keq is greater than 1 and delta G is negative for a particular reaction done at standard conditions, in which direction will the reaction proceed? Well, it will proceed forward and let's just take a look at this. So if we have Keq greater than 1, that means that remember Keq, we're looking at the rate of formation of products over the rate of disappearance of reactants. So if there's a greater rate of formation of products, that means that our keq KEQ will be greater than 1. However, if our KEQ is less than 1, that means means that there was more The rate of formation of reactants was greater than the rate of formation of products, meaning that you know, that the sort of the, in terms of the kinetics of that reaction, it's looking in the reverse direction. And lastly, if KEQ is equal to 1. What do you think that means? What do you think it means if the rate of formation of our products is the same as the rate of formation of our reactants? Well, that means that we're at important to also consider your delta Gs here. So, if Keq is greater than 1 and delta G is negative or just put that out front actually, right? That makes more sense. Negative delta G. That means that you have a reaction that is going to, spontaneously proceed forward. So this is going to go forward. If your Keq is equal to 1 and your Delta G is equal to 0, again, you are at equilibrium. And lastly, if your Delta G is positive and your Keq is greater than or sorry less than 1, you're going to go the reverse direction. So, in this case, we have these conditions up top meaning our reaction is going to proceed forward. Alright. Let's look at question 10. Which of the following is not correct? The answer here is E, phosphocreatine. Phosphocreatine has a delta G that's basically negative 43 kilojoules per mole. Meaning, it's actually greater than that of ATP ATP because ATP you might recall is about 30 kilojoules per mole. So phosphocreatine actually is a, a greater delta g than ATP or a more negative delta g, I should say. And yeah. A a through d, these are all correct value ranges. Now, let's take a look at 11. Delta G on the reaction, studentose 2 protocate is negative 35 kilojoules from per mole. This means that under standard conditions, the reaction will What does it mean if we have negative delta G? What does delta G tell us about a reaction? It tells us whether or not a reaction will occur spontaneously. It doesn't indicate how fast that reaction is going to proceed though. So, that's a big important difference to keep in mind that delta G just tells you whether or not it's going to happen spontaneously, meaning whether or not it's going to happen on its own. It doesn't mean it will happen quickly. There are a lot of spontaneous reactions that are incredibly slow. So, our answer here is E, will proceed spontaneously from student host to pro proddicate. If it was positive, then it would not occur spontaneously. And if it was 0, it would be at equilibrium. So let's move on to question 12. Which of the following has the largest negative value for delta G of hydrolysis? So this is very similar to question 10, right? Now, we're we're almost doing the opposite of question 10 here, right? So, what has the largest negative value for hydrolysis and of the molecules listed, it is acid anhydrides. And remember, those range from about negative 30 to 40 kilojoules per mole and that includes ATP. ATP is an acid in hydride. All right. Let's take a look at question 13. So, let's consider the malate dehydrogenase reaction. We have a delta G in the positive range and this reaction takes malate and NAD plus and turns into oxaloacetate and NADH and we're actually going to take a look at this reaction much more detail in the next unit. We talk about citric acid cycle but for now, looking at this, what is the answer here? The reaction as written may actually occur at some concentrations of substrates and products, in certain cells. Now, remember back to our glycolysis reactions. We had that one reaction that at these bio chemical conditions, delta g prime not, it had a positive delta g, right? But its cellular conditions, It's delta g was closer to 0, right? So bear in mind that the reaction they're showing us, they're saying that delta G, this is delta G naught or prime naught though. That has a positive value but it's possible. We don't know. It's possible that in cells at certain concentrations of substrates and products, this delta G might actually might actually be closer to 0 or even negative. So, it's we don't know that it can never occur can occur if it's coupled with a positive delta G prime reaction. And can occur cannot occur at all because of its activation energy and does not even occur in biochemics. No way. So may occur depending on the conditions in the cell and think about that reaction that we we talked about, before that had a positive delta G in these conditions but in cellular conditions actually had delta G closer to 0. Alright. Let's flip the page.