Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 9.3: The citric acid cycle completes the energy-yielding oxidation of organic molecules Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links the cycle to glycolysis

LE 9-10 CYTOSOL Pyruvate NAD + MITOCHONDRION Transport protein NADH + H + Coenzyme ACO 2 Acetyl Co A To convert pyruvate to Acetyl CoA: CO 2 is removed A Hydrogen is removed by NAD making NADH Coenzyme A is added

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The citric acid cycle, also called the Krebs cycle, takes place within the mitochondrial matrix The cycle oxidizes organic fuel derived from pyruvate, generating one ATP, 3 NADH, and 1 FADH 2 per turn So per glucose molecule you get 2 ATP, 6 NADH, and 2 FADH 2 Animation: Electron Transport Animation: Electron Transport

LE 9-11 Pyruvate (from glycolysis, 2 molecules per glucose) ATP Glycolysis Oxidation phosphorylation Citric acid cycle NAD + NADH + H + CO 2 CoA Acetyl CoA CoA Citric acid cycle CO NAD H + NADH3 ATP ADP + P i FADH 2 FAD

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The citric acid cycle has eight steps, each catalyzed by a specific enzyme The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle The NADH and FADH 2 produced by the cycle relay electrons extracted from food to the electron transport chain

LE 9-12_1 ATP Glycolysis Oxidation phosphorylation Citric acid cycle Citric acid cycle Citrate Isocitrate Oxaloacetate Acetyl CoA H2OH2O

LE 9-12_2 ATP Glycolysis Oxidation phosphorylation Citric acid cycle Citric acid cycle Citrate Isocitrate Oxaloacetate Acetyl CoA H2OH2O CO2CO2 NAD + NADH + H +  -Ketoglutarate CO2CO2 NAD + NADH + H + Succinyl CoA

LE 9-12_3 ATP Glycolysis Oxidation phosphorylation Citric acid cycle Citric acid cycle Citrate Isocitrate Oxaloacetate Acetyl CoA H2OH2O CO2CO2 NAD + NADH + H +  -Ketoglutarate CO2CO2 NAD + NADH + H + Succinyl CoA Succinate GTP GDP ADP ATP FAD FADH 2 P i Fumarate

LE 9-12_4 ATP Glycolysis Oxidation phosphorylation Citric acid cycle Citric acid cycle Citrate Isocitrate Oxaloacetate Acetyl CoA H2OH2O CO2CO2 NAD + NADH + H +  -Ketoglutarate CO2CO2 NAD + NADH + H + Succinyl CoA Succinate GTP GDP ADP ATP FAD FADH 2 P i Fumarate H2OH2O Malate NAD + NADH + H +

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Summary of Krebs Cycle