1. Unit 2: Metabolic Processes The Krebs Cycle
SBI4U – Ms. Richardson

2. Krebs Cycle
1937, Sir Hans Krebs discovered a series of metabolic reactions, later winning the Nobel Prize
9 reactions, aerobic – requires oxygen
Occurs in the mitochondrial matrix
Net 2 ATP produced
The cycle begins and ends with oxaloacetate
Acetyl-CoA enters cycle and assists in forming citrate (citric acid) from oxaloacetate

3. Krebs Cycle oxaloacetate + acetyl-CoA + ADP + Pi + 3NAD+ + FAD 
CoA + ATP + 3NADH + 3H+ + FADH2 + 2CO2 + oxaloacetate
Occurs twice for every molecule of glucose
(1 glucose  2 pyruvate  2 acetyl-CoA)
CoA gets recycled

4. Krebs Cycle For each Acetyl-CoA: 3 NADH 1 FADH2 1 ATP 2 CO2
For each glucose:
6 NADH
2 FADH2
2 ATP
4 CO2

5. Summary of Reactions Reaction 1: Condensation
Reaction 2-3: Isomerization
Reaction 4: 1st Oxidation
Reaction 5: 2nd Oxidation
Reaction 6: Substrate Level Phosphorylation
Reaction 7: 3rd Oxidation
Reaction 8: Regeneration of oxaloacetate, 4th Oxidation

6. Krebs Cycle