Lecture 11 -- Central Metabolism II

Question 1

• glucose + oxygen –> carbon dioxide + water + ATP

Answer 1

Aerobic Respiration

Question 2

• Pyruvate dehydrogenase

Answer 2

What couples gycolysis to the TCA cycle

Question 3

• pyruvate converted to acetyl CoA
• NAD+ picks up two electrons
• releases CO2
  (happens twice bc 2 pyruvate molecules)
• involves co-factors such as TPP, FAD, pioic acid, NAD+ and coenzyme A, can be large complex

Answer 3

Pyruvate dehydrogenase reaction

Question 4

mainly glycolysis (can also come from beta oxidation of fatty acids or amino acid catabolism)

Answer 4

What generates the majority of acetyl-CoA?

Question 5

• Acetyl-CoA entry point
• Isocitrate dehydrogenase (NAD+ picks up electrons and CO2 released)
• alpha-ketoglutarate dehydrogenase “”
• Succinate thiokinase produces GTP = ATP
• Succinate dehydrogenase FAD picks up electrons
• Malate Dehydrogenase NAD+ picks up electrons

*Oxaloacetate is required

Answer 5

Important TCA details

Question 6

2C + 4C –> 6C –> 5C + 1C –> 4C + 1C

Answer 6

carbon balance for TCA

Question 7

• oxaloacetate can make amino acids/feed into gluconeogenesis
• acetyl-CoA can make fatty acids or isoprenoids
• alpha-ketoglutarate can make amino acids
• succinyl coA can make lysine, methionine, cytochromes, and chlorophylls

Answer 7

TCA as an anabolic process

Question 8

• regenerating substrate
• depletion will terminate the TCA cycle
• depleted because TCA is anabolic

Answer 8

Oxaloacetate

Question 9

• bacteria grown on amino acids or organic acids
• can use pyruvate carboxylase (forward direction) or phosphoenolpyruvate carboxykinase (reverse direction)
• first requires ATP, second produces ATP

Answer 9

How is oxaloacetate replenished?

Question 10

The glyoxylate shunt because it results in anabolism to 4C compounds rather than catabolism to 1C compounds

Answer 10

What do bacteria use when grown on acetate or fatty acids?

Question 11

• no ATP formation
• no decarboxylation
• uses additional acetyl-CoA
• replenishes oxaloacetate

Answer 11

Features of the glyoxylate shunt

Question 12

• Isocitrate lyase increases pathway and has a high Km (requires high concentration of isocitrate)
• Malate synthase converts glyoxylate to malate
• inhibition of isocitrate dehydrogenase

Answer 12

How is the glyoxylate shunt regulated?