Citric Acid Cycle and Oxidative Phosphorylation (Lec 5)

Question 1

Cellular Respiration

Answer 1

Process in which cells consume O2 and produce CO2. Occurs in 3 major stages:

1. Acetyl-CoA production
2. Acetyl-CoA oxidation
3. Electron Transfer and Oxidative Phosphorylation

Question 2

Respiration: Stage 1

Answer 2

Acetyl-CoA Production: Generates some ATP + NADH. Common final product is Acetyl CoA

Question 3

Respiration: Stage 2

Answer 3

Acetyl-CoA Oxidation: Occurs in the mitochondria. Generates more NADH, FADH2 (e-) and one GTP. Remaining carbon atoms from carbohydrates, amino acids, and fatty acids are released during Stage 2.

Question 4

Respiration: Stage 3

Answer 4

Oxidative Phosphorylation: Occurs in mitochondria. Generates the vast majority of ATP during catabolism

Question 5

Conversion of Pyruvate to Acetyl-CoA

Answer 5

Highly thermodynamically favourable, irreversible reaction. - Generates NADH

• Produces CO2
• Catalyzed by Pyruvate Dehydrogenase Complex (PDC)

Question 6

Pyruvate Dehydrogenase Complex (PDC)

Answer 6

Catalyzes conversion of Pyruvate to Acetyl-CoA. Multienzyme subunit that channels substrates from one enzyme to another, so as to minimalise side reactions

Question 7

Citric Acid Cycle: Steps

Answer 7

1. C-C bond formation between acetate (2C) and oxaloacetate (4C) to make citrate (6C)
2. Isomerization via hydration/dehydration
   3-4. Oxidative decarboxylations to give 2 NADH
3. Substrate-level phosphorylation to give ATP
4. Dehydrogenation to give FADH2
5. Hydration
6. Dehydrogenation to give NADH