Citric Acid Cycle (TCA)

Where does the citric acid cycle occur?

In the mitochondrial matrix

Step 1

Oxaloacetate + Acetyl CoA → Citrate

• Enzyme: Citrate synthase

Step 2

Citrate → Isocitrate

• Enzyme: Aconitase

Step 3

Isocitrate + NAD+→ α-Ketoglutarate + CO2 + NADH

• Enzyme: Isocitrate Dehydrogenase

• Rate-limiting step

Step 4

α-Ketoglutarate + NAD+→ Succinyl-CoA + CO2 + NADH

• Enzyme: α-Ketoglutarate dehydrogenase

Step 5

Succinyl-CoA + GDP→ Succinate + GTP

• Enzyme: Succinyl-CoA synthetase

Step 6

Succinate + FAD → Fumarate + FADH2

• Enzyme: Succinate Dehydrogenase

Step 7

Fumarate → Malate

• Enzyme: Fumarase

Step 8

Malate + NAD+→ Oxaloacetate + NADH

• Enzyme: Malate Dehydrogenase

What is the purpose of the TCA?

To make electron carriers for teh ETC

What is the overall equation

1 Acetyl-CoA → 3 NADH + 1 FADH₂ + 1 ATP + 2 CO₂