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Pyruvate Oxidation or Oxidative Decarboxylation (if oxygen is present…)

Pyruvate Oxidation or Oxidative Decarboxylation (if oxygen is present…). The following occurs for each pyruvate: CO 2 removed. NAD + reduced to NADH and the 2-carbon compound becomes acetic acid. Coenzyme A (CoA) attaches to acetic acid to form acetyl-CoA.

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Pyruvate Oxidation or Oxidative Decarboxylation (if oxygen is present…)

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  1. Pyruvate Oxidation or Oxidative Decarboxylation(if oxygen is present…) The following occurs for each pyruvate: • CO2 removed. • NAD+ reduced to NADH and the 2-carbon compound becomes acetic acid. • Coenzyme A (CoA) attaches to acetic acid to form acetyl-CoA.

  2. Pyruvate Oxidation or Oxidative Decarboxylation

  3. Pyruvate Oxidation or Oxidative Decarboxylation Energy Yield & Products: 2 NADH 2 acetyl-CoA 2 CO2 (released as waste)

  4. Acetyl-CoA • CoA comes from vitamin B5 • Proteins, lipids, and carbohydrates are catabolized to ‘acetyl-CoA’ • It can be used to make fat or ATP • [ATP] determines what pathway this molecule takes • If O2 is present, ‘acetyl CoA’ moves to the Kreb’s Cycle (aerobic respiration) • If O2 is NOT present, ‘acetyl CoA’ becomes ‘lactate’ (anaerobic respiration / fermentation)

  5. Krebs cycle - overview • 8 step process, with each step catalyzed by a specific enzyme • It is a ‘cycle’ because oxaloacetate is the product of step 8, and the reactant in step 1 • REMEMBER: Two acetyl-CoA molecules enter, so the Krebs Cycle must happen TWICE for every one molecule of glucose that begins glycolysis

  6. The Krebs Cycle Occurs twice for each molecule of glucose, 1 for each acetyl-CoA.

  7. The Krebs Cycle – Key Features • In step 1, acetyl-CoA combines with oxaloacetate to form citrate. • NAD+ is reduced to NADH in steps 3, 4 and 8. • FAD is reduced to FADH2 in step 6. • 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. • CO2 is released in steps 3 and 4.

  8. The Krebs Cycle Energy Yield & Products: 2 ATP 6 NADH 2 FADH2 4 CO2 (released as waste) NADH and FADH2 carry electrons to the electron transport chain for further production of ATP by oxidative phosphorylation.

  9. Cellular Respiration so far has produced… • Glycolysis • 2 ATP (net) • 2 NADH, converted to 2 FADH2 • Pyruvate Oxidation • 2 NADH • Krebs Cycle • 2 ATP • 6 NADH • 2 FADH2

  10. E.T.C. - Structure • A series of electron acceptors (proteins) are embedded in the inner mitochondrial membrane. • These proteins are arranged in order of increasing electronegativity. • The weakest attractor of electrons (NADH dehydrogenase) is at the start of the chain and the strongest (cytochrome oxidase) is at the end. • Since the mitochondrial membrane is highly folded, there are multiple copies of the ETC across the membrane

  11. Electron Transport Chain - Overview • NADH and FADH2 transfer electrons to proteins in the inner mitochondrial membrane • The weakest electron attractors are at the start, and the strongest are at the end • Each component is REDUCED, and then subsequently OXIDIZED • Oxygen (highly electronegative) oxidizes the last ETC component • The energy released, moves H+ atoms (i.e. protons) across mitochondrial membrane

  12. Electrochemical gradient is created, with a lot of H+ outside Sets the rate of this process… The energy stored in the [] gradient will be used in the second part of the ETC to power ATP synthesis

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