The Krebs Cycle: Understanding Cellular Respiration

1. aerobic – require oxygen 3 parts of Respiration • Glycolysis – may be anaerobic • TCA – Kreb’s Cycle • Electron Transport Chain

2. Krebs Cycle • Pyruvate enters the mitochondrial matrix and enters a preparatory step before entering the Kreb’s Cycle. • Refer to handout

3. Krebs Cycle • Pyruvate enters the mitochondrial matrix and is converted into acetyl coenzyme A (2-carbon molecule)

4. Krebs Cycle • Acetyl CoA combines with oxaloacetate to form citrate (citric acid). CoA is released, awaiting another pyruvate molecule. • Citrate loses water, converts to cis-Aconitate. Cis-Aconitate gains water to become isocitrate

5. Kreb’s Cycle • An NAD+ is reduced to NADH converting isocitrate into oxalosuccinate. • Oxalosuccinate loses a Carbon and becomes α-Ketoglutarate

6. Krebs Cycle • α-Ketoglutarate (5-C) loses a Carbon and becomes succinyl-CoA; another NAD+ is reduced

7. Krebs Cycle • Succinyl-CoA releases the CoA, forming succinate. At the same time, a GDP molecule is phosphorylated to make GTP. GTP transfers its P to ADP to make ATP

8. Krebs Cycle • Succinate is converted into fumarate by reducing FAD+ into FADH2

9. Krebs Cycle • Fumarate reacts with water to form a molecule of malate

10. Krebs Cycle • Malate is converted into oxaloacetate by reducing another NAD+ into NADH + H+ • Oxaloacetate gets recycled

11. Output of one pyruvate From prep step 1 CO2 1NADH + H+ From Krebs alone 2 CO2 3 NADH + H+ 1 FADH2 1 ATP What would the output be of ONE GLUCOSE molecule after the Krebs Cycle? Krebs Cycle