Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
6 Cards in this Set
- Front
- Back
|
3. The partial reactions leading to the synthesis of acyl CoA (equations 1 and 2, Section 27.1) are freely reversible. The equilibrium constant for the sum of these reactions is close to 1, meaning that the energy levels of the reactants and products are about equal, even though a molecule of ATP has been hydrolyzed. Explain why these reactions are readily reversible. |
The ready reversibility is due to the high-energy nature of the thioester in the acyl CoA. |
|
|
12. Counting ATPs 1. What is the ATP yield for the complete oxidation of C17 (heptadecanoic) fatty acid? Assume that the propionyl CoA ultimately yields oxaloacetate in the citric acid cycle. |
Activation fee to form the acyl CoA −2ATP Seven rounds of yield:
7 acetyl CoA 10 ATP/acetyl CoA +70 ATP
7 NADH at 2.5 ATP/NADH +17.5 ATP 7 FADH2 at 1.5 ATP/FADH2 +10.5 ATP Propionyl CoA to succinyl CoA −1 ATP Succinyl CoA → succinate +1 ATP Succinate → fumarate + FADH2 FADH2 at 1.5 ATP/FADH2 +1.5 ATP Fumarate → malate Malate → oxaloacetate + NADH NADH at 2.5 ATP/NADH +2.5ATP
Total: 100 ATP |
|
|
15. Compare the ATP yield from the complete oxidation of glucose, a six-carbon carbohydrate, and hexanoic acid, a six-carbon fatty acid. Hexanoic acid is also called caproic acid and is responsible for the “aroma” of goats. Why are fats better fuels than carbohydrates? |
The total for glucose is 30 ATP. Now, what about hexanoic acid? Caproic acid is activated to caproic CoA at the expense of 2 ATP, and so we are 2 ATP in the hole. The first cycle of β oxidation generates 1 FADH2, 1 NADH, and 1 acetyl CoA. --> 14 ATP The second cycle ofβ oxidation generates 1 FADH2 and 1 NADH but 2 acetyl CoA. After the acetyl CoA has been run through the citric acid cycle, this step will have generated a total of 24 ATP. The total is 36 ATP. Thus, the foul-smelling caproic acid has a net yield of 36 ATP. |
|
|
25. What is the purpose of protein degradation during the initial stages of starvation? |
The carbon skeletons of the released amino acids are used to synthesize glucose for use by the brain and red blood cells. |
|
|
28. We encountered reactions similar to the oxidation, hydration, and oxidation reactions of fatty acid degradation earlier in our study of biochemistry. What other pathway employs this set of reactions? |
The citric acid cycle. The reactions that take succinate to oxaloacetate, or the reverse, are similar to those of fatty acid metabolism. |
|
|
29. Ill-advised diet. Suppose that, for some bizarre reason, you decided to exist on a diet of whale and seal blubber, exclusively. (a) How would a lack of carbohydrates affect your ability to utilize fats? (b) What would your breath smell like? (c) One of your best friends, after trying unsuccessfully to convince you to abandon this diet, makes you promise to consume a healthy dose of odd-chain fatty acids. Does your friend have your best interests at heart? Explain. |
A. Without carbohydrates, there would be no anapleurotic reactions to replenish the components of the citric acid cycle.With a diet of fats only, the acetyl CoA from fatty acid degradation would build up. B. Acetone from ketone bodies C.Yes. Odd-chain fatty acids would lead to the production of propionyl CoA, which can be converted into succinyl CoA, a citric acid cycle component. It would serve to replenish the citric acid cycle and mitigate the halitosis. |
