The TCA Cycle in Eukaryotic Cells

Where does the TCA cycle occur in eukaryotic cells?

Mitochondrial matrix

What mitochondrial structure increases surface area for energy production?

Cristae (inner membrane folds)

What happens to pyruvate before entering TCA cycle?

Converted to acetyl-CoA by PDH complex (releases CO₂ + makes NADH)

What vitamin deficiency disrupts pyruvate conversion?

Thiamine (B1) deficiency → beriberi

First reaction of TCA cycle?

Acetyl-CoA + oxaloacetate → citrate (via citrate synthase)

Which steps release CO₂?

Step 3 (isocitrate→α-KG) and Step 4 (α-KG→succinyl-CoA)

what is the only membrane-bound TCA enzyme?

Succinate dehydrogenase (also ETC Complex II)

what is the energy yield per acetyl-CoA?

3 NADH + 1 FADH₂ + 1 GTP (= ~10 ATP via ETC)

what is the total ATP from 1 glucose via TCA + ETC?

38 ATP (2 from glycolysis + 2 from PDH + 30 from TCA/ETC)

Which TCA step makes GTP directly?

Succinyl-CoA → succinate (substrate-level phosphorylation)

Why is oxaloacetate important?

Regenerated to keep cycle running (accepts new acetyl-CoA)

What's unique about α-KG dehydrogenase?

Uses same cofactors as PDH complex (TPP, lipoamide, etc.)