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Chapter 16.2: The Citric Acid Cycle. CHEM 7784 Biochemistry Professor Bensley. CHAPTER 16 The Citric Acid Cycle. Today’s Objectives: (To learn and understand the). Reactions of the citric acid cycle. Respiration: Stage 1. Generates some: ATP, NADH, FADH 2. Respiration: Stage 2.
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Chapter 16.2: The Citric Acid Cycle CHEM 7784 Biochemistry Professor Bensley
CHAPTER 16The Citric Acid Cycle Today’s Objectives: (To learn and understand the) • Reactions of the citric acid cycle
Respiration: Stage 1 Generates some: ATP, NADH, FADH2
Respiration: Stage 2 Generates more NADH, FADH2 and one GTP
The Citrate Synthase Reaction (Step #1) • The only cycle reaction with C-C bond formation • Essentially irreversible process
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 The Isocitrate Dehydrogenase Reaction (Step #3)
Acetyl-CoA + 3NAD+ + FAD + GDP + Pi + 2 H2O 2CO2 +3NADH + FADH2 + GTP + CoA + 3H+ Net Effect of the Citric Acid Cycle • Carbons of acetyl groups in acetyl-CoA are oxidized to CO2 • 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
Chapter 16: Summary In this chapter, we learned that: • 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