Reading Guide, Stryer Short Course, Chapter 19
1.Use the citric acid cycle worksheet to help in learning the citric acid cycle.
2. The citric acid cycle is a series of redox reaction that ultimately converts the acetyl group of acetyl CoA into ______. In other words, the function of the citric acid cycle is the harvesting of ______from carbon fuels.
3. Notice that the citric acid cycle itself does not generate much ______nor include ______as a substrate. Instead, it captures high energy electrons to form ______, which are eventually oxidized.
4. In the first step, ______and ______react to form the 6-carbon compound, citrate. In essence, it is the hydrolysis of the ______that makes this reaction irreversible.
5. In the first step, ______prevents an undesireable side reaction.
6. Citrate is isomerized to isocitrate to enable the 6-carbon unit to undergo ______.
7. In step 3, oxidation of the fuel leads to reduction of ______to ______. This is made irreversible by the loss of ______gas.
8. Step 4 is also an oxidative decarboxylation, but because it is decarboxylation of an-ketoacid, it requires the cofactor ______.
9. Stage two of the citric acid cycle is the regeneration of ______, which involves two more oxidations and a substrate level phosphorylation.
10. The free energy of succinyl CoA hydrolysis is used to power formation of ______.
11. In the mechanism of succinyl CoA synthetase, the high energy bond ______is transformed into the high energy bond ______, which leads to phosphorylation of the enzyme on a ______residue, then finally to formation of ______.
12. Draw the three-reaction transformation of succinate to oxaloacetate. (You need to know this basic pathway well because it shows up again.)
13. What is the energetic reason that FAD is used in some reaction rather than NAD+.
14. The net oxidation of an acetyl group has produced ___ CO2, ___ ATP, ___ NADH, and ___ FADH2.
15. Isotopic labeling studies show that the two carbons that enter the cycle are not the two that ______.
16. Details will be discussed in a later section, but oxidation of NADh can produce about ______ATP. Oxidation of FADH2 result in formation of about _____ ATP. Therefore, one complete turn of the citric acid cycle will produce about ______ATP.
17. True or false: Glycolysis has both an aerobic and and anaerobic mode, whereas the citric acid cycle is strictly aerobic.
18. The irreversible steps of the citric acid cycle are downregulated allosterically by ______, which signals high energy charge, and _____ which signals a high reducing potential.
19. Inhibition of isocitrate DH leads to a buildup of ______, which acts as an inhibitor of the ______pathway.
20. To understand the citric acid cycle, you must realize that, in addition to its role in the production of ATP, it also provides ______.
21. What problem would arise if oxaloacetate were converrted into glucose, then subsequently, the energy needs of the cell arise?
22. What is the first step in gluconeogenesis? What role does it play in the citric acid cycle?
23. An ______reaction leads to the net synthesis or replenishment of pathway components.
24. Most organisms cannot convert ______into net glucose.
25. In plants, the glyoxylate pathway allows for conversion of ______into net ______. This pathway bypasses the two oxidative decarboxylation steps to allow two acetyl CoA into the four carbon compound ______.