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

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

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

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

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

Krebs Cycle