Krebs Cycle

Question 1

Step 0

Answer 1

Pyruvate Dehydrogenase converts Pyruvate into Acetyl CoA.

Regulation: Inhibited by [NADH] and [Acetyl CoA].

Question 2

Step 1

Answer 2

Citrate Synthase converts Acetyl CoA & Oxaloacetate into Citrate.
Regulation: Inhibited by [NADH] and [Citrate].

Question 3

Step 2

Answer 3

Aconitase isomerizes citrate into isocitrate.

Regulation: inhibited by [Isocitrate].

Question 4

Step 3

Answer 4

Isocitrate Dehydrogenase converts Isocitrate into a-Ketoglutarate.
Regulation: Inhibited by [NADH] and [ATP].
Yields: 1 NADH

Question 5

Step 4

Answer 5

a-Ketogularate Dehydrogenase converts a-Ketoglutarate into Succinyl-CoA.
Regulation: inhibited by [NADH] and [Succinyl-CoA].
RATE LIMITING

Question 6

Step 5

Answer 6

Succinyl CoA Synthetase converts Succinyl CoA into Succinate via phosphorylation.
Regulation: Reversible
Yields: 1 ATP/GTP

Question 7

Step 6

Answer 7

Succinate Dehydrogenase converts Succinate into Fumarate via Oxidation.
Regulation: None.
Yields: FADH2

Question 8

Step 7

Answer 8

Fumarase converts Fumarate into Malate via Reduction.

Regulation: Reversible

Question 9

Step 8

Answer 9

Malate Dehydrogenase converts Malate into Oxaloacetate via oxidation.
Regulation: Reversible
Yields: 1 NADH.

Question 10

Net Yield

Answer 10

2 CO2, 1 ATP/GTP, 3 NADH, 1 FADH2.

Question 11

Anaplerosis

Answer 11

Reactions that form intermediates of a reaction pathway.

Question 12

a-Ketoglutarate Replenishment

Answer 12

Glutamate forms a-ketoglutarate by transamination. This removes the amine group from the amino side of the amino acid and forms NADH.

Question 13

Succinyl CoA Replenishment

Answer 13

Succinyl CoA is made from Propionyl CoA. Propionyl CoA is formed from odd-chained fatty acids, and leucine, isoleucine, valine, threonine and methionine.

Question 14

Oxaloacetate Replenishment

Answer 14

Pyruvate Carboxylase forms Oxaloacetate from Pyruvate in Mito. Can be retained for the ETC or exported for Gluconeogenesis.