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Pyruvate Oxidation & Krebs Cycle!!

Stage 2 & 3 of Cellular Respiration. Pyruvate Oxidation & Krebs Cycle!!. ATP. ATP. 2. 4. 2. 2. 4. ADP. ADP. NAD +. 2 P i. 2. 2 P i. 2 H. Review. glucose C-C-C-C-C-C. 10 reactions convert glucose (6C) to 2 pyruvate (3C) produces: 4 ATP & 2 NADH consumes: 2 ATP

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Pyruvate Oxidation & Krebs Cycle!!

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  1. Stage 2 & 3 of Cellular Respiration Pyruvate Oxidation & Krebs Cycle!!

  2. ATP ATP 2 4 2 2 4 ADP ADP NAD+ 2Pi 2 2Pi 2H Review glucose C-C-C-C-C-C • 10 reactions • convert glucose (6C)to 2 pyruvate (3C) • produces:4 ATP & 2 NADH • consumes:2 ATP • net:2 ATP & 2 NADH fructose-1,6bP P-C-C-C-C-C-C-P DHAP P-C-C-C G3P C-C-C-P pyruvate C-C-C

  3. glucose      pyruvate 6C 3C 2x pyruvate      CO2 Glycolysis is only the start • Glycolysis • Pyruvate has more energy to yield • 3 more C to strip off (to oxidize) • if O2 is available, pyruvate enters mitochondria • enzymes of Krebs cycle complete the full oxidation of sugar to CO2 3C 1C

  4. Cellular respiration

  5. outer membrane intermembrane space inner membrane cristae matrix mitochondrialDNA Mitochondria — Structure • Doubled-membrane, energy-harvesting organelle • smooth outer membrane • highly folded inner membrane • Called cristae • intermembrane space • fluid-filled space between membranes • matrix • inner fluid-filled space • Contains DNA, ribosomes, enzymes

  6. NAD+ 2 x[ ] Pyruvate oxidized to Acetyl CoA reduction Acetyl CoA Coenzyme A CO2 Pyruvate C-C C-C-C oxidation Yield = 2C sugar + NADH +CO2 +H+

  7. Pyruvate Oxidation • multi-enzyme complex catalyzes the following three changes: • the carboxyl group of pyruvate is removed as a CO2 molecule. This is a decarboxylation reaction catalyzed by the enzyme pyruvatedecarboxylase. • The 2-C fragment is oxidized to form an acetate ion. Electrons from this reaction are picked up by NAD+ which is reduced to form NADH + H+ • The acetyl group of the acetate ion is transferred to coenzyme A, forming acetyl CoA

  8. [ ] 2x NAD Pyruvate Oxidation • Pyruvate enters mitochondria • 3 step oxidation process • releases 1 CO2(count the carbons!) • reduces 2NAD  2 NADH (moves e-) • produces acetyl CoA • Acetyl CoA enters Krebs cycle pyruvate  acetyl CoA + CO2 1C 3C 2C Wheredoes theCO2 go? Exhale!

  9. Krebs Cycle • The Krebs cycle is an 8-step cyclic process that oxidizes acetyl-CoA to carbon dioxide and water, forming a molecule of ATP. • In addition, the cycle removes electrons, which are carried by 3 NADH and 1 FADH2 molecules to the electron transport chain. • The following is the overall chemical equation: • oxaloacetate + acetyl-CoA + ADP + Pi + 3NAD+ + FAD ---> CoA+ ATP + 3 NADH + 3H+ + FADH2 + 2CO2 + oxaloacetate

  10. Production of Citrate • The energy in acetyl CoA drives the reaction of acetate with oxaloacetate to produce citrate. • The Krebs cycle or citric acid cycle is a series of reactions in which citrate is oxidized and oxaloacetate regenerated. • It produces two CO2 , one FADH2, three NADH, and one ATP for each acetyl CoA.

  11. Krebs Cycle - Highlights • In step 1, acetyl-CoA combines with oxaloacetate to form citrate. • In step 2, citrate is rearranged to isocitrate. • NAD+ is reduced to NADH in steps 3, 4 and 8. • CO2 is released in steps 3 and 4. • FADis reduced to FADH2 in step 6.

  12. Krebs Cycle - Highlights • ATP if formed in step 5 by substrate-level phosphorylation. The phosphate group from succinyl-CoA is transferred to GDP, forming GTP, which then forms ATP. • In step 8, oxaloacetate is formed from malate, which is used as a reactant in step 1.

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