For the first step in fatty acid catabolism, we say that ATP is used to “drive” the reaction that links the fatty acid with coenzyme-A. Without ATP hydrolysis, would you predict that the linking of fatty acid to coenzyme-A would be exergonic or endergonic? In fatty acid CoA synthesis, the hydrolysis of the ATP portion is based on what major strategy of metabolism?

Question

Accepted Answer

Alright. Hello everyone. So this question says during glycolysis, glucose is converted into pyruvate with several intermediate steps involving phosphorylation by A TP. Without these phosphorylation steps driven by ATP hydrolysis, would these reactions be exer agonic or ender agonic in these reactions? The hydrolysis of the ATP portion is based on what major strategy of metabolism. So first and foremost, right, what steps of glycolysis is the question referring to? Well, recall that in glycolysis, there are two main steps that involve a phosphorylation. The first is the hex kinase reaction in which we go from glucose. That's the starting material to let me actually fix that arrow. But in any case, during the hexokinase reaction, we go from glucose to glucose, six phosphate or glucose six P for short, the other reaction is the possible fructose tiniest reaction. And as a result of the phosphofructokinase reaction, we take fructose six phosphate and create fructose 16 bisphosphate, but I ran out of space. So let me just move this to the side. So as mentioned before, these are the two phosphorylation reactions in glycolysis. So here, right, the reason why A TP is necessary is first of all, to provide this extra phosphate group that's being added onto our starting materials. But also why is the hydrolysis of a TP important for these steps? Aside from, as mentioned before being the source of the phosphate group that's being added. Well, recall that the hydrolysis of A TP reduce excuse me, releases a lot of energy and sometimes that energy that's being released is needed to be put in to make certain reactions take place. So, phosphorylation steps are helpful because they make certain reactions ergo meaning they will release energy when they otherwise would be ender thereby requiring energy. So going back to the statement at hand here, these two reactions of the glycolysis pathway would be ergo without the hydrolysis of ATP because without a TP, some form of energy needs to be put in. And so that energy released from hydrolyzing A TP would then be devoted to making these reactions go forward or proceed forward. So main point is that the two phosphorylation reactions of glycolysis would be endon without a TP. So what does it mean when we pair an ender agonic reaction with a highly exon reaction such as ATP hydrolysis? Well, that if you recall is known as coupling, so we are coupling these two reactions together, we are pairing these two reactions together. So when we combine an ender agonic reaction with a highly exergen reaction, the overall delta G value, the overall jibs free energy change of the combined reaction will be less than zero, it will be negative thereby driving the reaction forwards. So there you have it without a TP hydrolysis, the phosphorylation reaction would be endon and this major strategy of metabolism is known as coupling. So with that being said, thank you so very much for watching. And I hope you found this helpful.

Verified video answer for a similar problem:

Key Concepts

Exergonic vs. Endergonic Reactions

ATP Hydrolysis

Metabolic Strategies