Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Citric Acid Cycle Before the citric acid cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle. This step is carried out by a multienzyme complex that catalyses three reactions (blue numbers). Figure 9.10 MITOCHONDRION CYTOSOL CO2 Coenzyme A 3 1 2 Pyruvate Transport protein NAD NADH + H Acetyl CoA What is getting oxidized? • After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules • This process happens in the mitochondria of eukaryotic cells only when O2 is present. The Citric Acid Cycle • The citric acid cycle (also called the Krebs cycle) completes the break down of pyruvate to CO2. • The cycle oxidizes organic fuel (acetyl coA). • And generates 1 ATP, 3 NADH, and 1 FADH2 per turn. • How many of each does it make per glucose molecule? Figure 9.11 Pyruvate CO2 NAD CoA Summary Picture (the important stuff!) NADH + H Acetyl CoA CoA CoA Citric acid cycle 2 CO2 3 NAD FADH2 3 NADH FAD + 3 H ADP + P i ATP The citric acid cycle has eight steps, each catalyzed by a specific enzyme. Figure 9.12-1 Acetyl CoA CoA-SH 1 Oxaloacetate Citrate Citric acid cycle The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate. Figure 9.12-2 Acetyl CoA CoA-SH H2O 1 Oxaloacetate 2 Citrate Isocitrate Citric acid cycle The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle. Figure 9.12-3 Acetyl CoA CoA-SH H2O 1 Oxaloacetate 2 Citrate Isocitrate NAD Citric acid cycle 3 NADH + H CO2 -Ketoglutarate Figure 9.12-4 Acetyl CoA CoA-SH H2O 1 Oxaloacetate 2 Citrate Isocitrate NAD Citric acid cycle NADH 3 + H CO2 CoA-SH -Ketoglutarate 4 NAD NADH Succinyl CoA + H CO2 Figure 9.12-5 Acetyl CoA CoA-SH H2O 1 Oxaloacetate 2 Citrate Isocitrate NAD Citric acid cycle NADH 3 + H CO2 CoA-SH -Ketoglutarate 4 CoA-SH 5 NAD Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H CO2 Figure 9.12-6 Acetyl CoA CoA-SH H2O 1 Oxaloacetate 2 Citrate Isocitrate NAD Citric acid cycle Fumarate NADH 3 + H CO2 CoA-SH -Ketoglutarate 4 6 CoA-SH 5 FADH2 NAD FAD Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H CO2 Figure 9.12-7 Acetyl CoA CoA-SH H2O 1 Oxaloacetate 2 Malate Citrate Isocitrate NAD Citric acid cycle 7 H2O Fumarate NADH 3 + H CO2 CoA-SH -Ketoglutarate 4 6 CoA-SH 5 FADH2 NAD FAD Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H CO2 Figure 9.12-8 Acetyl CoA CoA-SH NADH The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain. + H H2O 1 NAD 8 Oxaloacetate 2 Malate Citrate Isocitrate NAD Citric acid cycle 7 H2O Fumarate NADH 3 + H CO2 CoA-SH -Ketoglutarate 4 6 CoA-SH 5 FADH2 NAD FAD Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H CO2 Concept Map – – – – – – – – – – – Cellular Respiration Aerobic Anaerobic Glycolysis The Citric Acid Cycle Oxidative Phosphorylation The Electron Transport Chain Fermentation ATP NADH NAD+ – – – – – – – – – – Carbon dioxide Oxygen Glucose Water H+ ions Membrane proteins Mitochondria Cytosol Eukaryotes Prokaryotes