1. Chapter 16.2: The Citric Acid Cycle CHEM 7784 Biochemistry Professor Bensley

2. CHAPTER 16 The Citric Acid Cycle –Reactions of the citric acid cycle Today’s Objectives: (To learn and understand the)

3. Respiration: Stage 1 Generates some:ATP, NADH, FADH 2

4. Respiration: Stage 2 Generates more NADH, FADH 2 and one GTP

6. The Citrate Synthase Reaction (Step #1) The only cycle reaction with C-C bond formation Essentially irreversible process

7. Isomerization of Citrate by Aconitase (Step #2)

8. The Isocitrate Dehydrogenase Reaction (Step #3) Oxidation of the alcohol to ketone involves the transfer of a hydride from the C-H of the alcohol to the nicotinamide cofactor – 3 step mechanism

11. Oxidation of  -ketoglutarate (Step #4)

12. Substrate-Level Phosphorylation (Step #5)

13. Succinate Dehydrogenase (Step #6)

14. Hydration of Fumarate to Malate (Step #7)

15. Oxidation of Malate to Oxaloacetate (Step #8)

16. Products from One Turn of the Cycle

17. Net Effect of the Citric Acid Cycle Acetyl-CoA + 3NAD + + FAD + GDP + P i + 2 H 2 O 2CO 2 +3NADH + FADH 2 + GTP + CoA + 3H + Carbons of acetyl groups in acetyl-CoA are oxidized to CO 2 Electrons from this process reduce NAD + and FAD One GTP is formed per cycle, this can be converted to ATP Intermediates in the cycle are not depleted

18. Direct and Indirect ATP Yield

19. Role of the Citric Acid Cycle in Anabolism

20. Chapter 16: Summary Citric acid cycle is an important catabolic process: it makes GTP, and reduced cofactors that could yield ATP Citric acid cycle plays important anabolic roles in the cell A large multi-subunit enzyme, pyruvate dehydrogenase complex, converts pyruvate into acetyl-CoA Several cofactors are involved in reactions that harness the energy from pyruvate The rules of organic chemistry help to rationalize reactions in the citric acid cycle In this chapter, we learned that: