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Pyruvate Oxidation & Kreb’s Cycle

Pyruvate Oxidation & Kreb’s Cycle. By Seung Youn Kim, Craig Day, Henry Zhao. STAGE 2: PYRUVATE OXIDATION (Fig. 14, P. 100) 2 pyruvate molecules formed in glycolysis transported through both mitochondrial membranes to the matrix where each molecule undergoes the following:.

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Pyruvate Oxidation & Kreb’s Cycle

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  1. Pyruvate Oxidation & Kreb’s Cycle By SeungYoun Kim, Craig Day, Henry Zhao

  2. STAGE 2: PYRUVATE OXIDATION (Fig. 14, P. 100) • 2 pyruvate molecules formed in glycolysis transported through both mitochondrial membranes to the matrix where each molecule undergoes the following: • removal of carboxyl (COO-) group catalysed by pyruvate decarboxylase (diffuses from the cell as CO2) • redox reaction oxidizes remaining 2-C portion to an acetyl group, reduces NAD+ to NADP • (2 H-atoms transferred to NAD+ 2 NADH proceed to electron transport and chemiosmosis stage for oxidative phosphorylation, 2 H+ remain dissolved in matrix) • coenzyme A (coA, a vitamin B5 derivative) forms a weak C-S bond with acetyl group to form acetyl-coA , which prepares the acetyl group for further oxidation in the Krebs cycle Summary Equation for Pyruvate Oxidation Carboxyl Group 2 pyruvate + 2 NAD+ + 2 coA  2 acetyl-coA + 2 NADH + 2 H+ + 2 CO2 oxidative phosphorylation dissolved diffused in electron transport andin matrix out of cell chemiosmosis stage THE KREBS CYCLE

  3. STAGE 3: THE KREBS CYCLE (Fig. 16, P. 102) • cyclic (one of final products is also one of initial reactants), 8-step process, each step catalysed by a specific enzyme • occurs twice for each glucose molecule (once for each acetyl-coA) transfers energy to ATP (directly via substrate-level phosphorylation), NADH, FADH2 while removing C-atoms as CO2  most of energy stored in: 4 ATP molecules (2 from glycolysis, 2 from Krebs cycle) and 12 reduced coenzymes (2 NADHeach from glycolysis and pyruvate oxidation)(6 NADH and 2 FADH2 from the Krebs cycle) which will be transferred to ATP in electron transport and chemiosmosis stage

  4. STAGE 3: THE KREBS CYCLE Enzymes • Tips • Ways to remember enzyme names • What is the product called • What function does enzyme complete • Add -ase

  5. Related Pathways

  6. Summary of Fate of Glucose C-atoms CCCCCC CCC + CCC  CC + CC + CO2 + CO2  CO2 + CO2 + CO2 + CO2 glucose (glycolysis) 2 pyruvate (pyruvate oxidation) 2 acetyl-coA + 2 CO2 (Krebs cycle) 4 CO2

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