Kreb's Cycle

Question 1

Overview

Answer 1

Substrate is acetyl CoA (from B-O2 and/or glucose O2), occurs in mitochondria. Overall strategy is to completely O2 acetyl-CoA to CO2. Produces lots of NADH, FADH2, GTP and ATP. Oxaloacetate must be regenerated to keep the cycle going.

Question 2

steps

Answer 2

Acetyl-CoA (2C) combines with oxaloacetate (4C) to form citrate (6C).

Citrate is rearranged into isocitrate through a dehydration–rehydration step.

Isocitrate undergoes decarboxylation, producing NADH and a 5C intermediate.

The 5C intermediate is decarboxylated again, forming another NADH and a 4C molecule.

Substrate-level phosphorylation occurs, generating ATP (or GTP) from the 4C intermediate.

FAD accepts electrons to become FADH₂, as the molecule is oxidised and then hydrated.

A final NADH is produced as the molecule is oxidised back to oxaloacetate, completing the cycle.

Question 3

Important features

Answer 3

During cycle, 2 C atoms come in and 2 are released.

Question 4

Products

Answer 4

3NADH, 1 FADH2 and a GTP. Each NADH gives around 2.5 ATP in ETC each FADH2 gives ~1.5 ATP. With GTP that’s ~10ATP per acetyl-CoA. But, ATP is not directly generated. Oxaloacetate is carrier molecule