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Energy Production

Energy Production. Oxidation & Reduction. Oxidation: removal of electrons from a molecule (sometimes along with a hydrogen proton); usually releases energy Reduction: addition of electrons to a molecule (sometimes along with a hydrogen proton)

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Energy Production

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  1. Energy Production

  2. Oxidation & Reduction • Oxidation: removal of electrons from a molecule (sometimes along with a hydrogen proton); usually releases energy • Reduction: addition of electrons to a molecule (sometimes along with a hydrogen proton) • Both must occur at the same time - when one molecule is oxidized, another is reduced

  3. Phosphorylation • Phosphorylation: addition of a phosphate group to a molecule • One example: addition of phosphate group to ADP to make ATP • ADP + P -----------> ATP • Energy is required to phosphorylate since a new covalent bond is formed

  4. Energy to phosphorylate comes from three sources • Substrate level: energy comes from chemical reactions (when substrate is converted to product) • oxidative: energy is released from the oxidation of a molecule • photo- : energy comes from light (photosynthetic bacteria)

  5. Carbohydrate Catabolism • Breakdown of carbohydrates into smaller molecules • energy is released in the oxidation of carbohydrates (usually glucose) • oxidation of glucose involves removal of hydrogen electrons • when electrons removed, covalent bond breaks, energy released, some absorbed by electrons

  6. Electrons (with energy) picked up by coenzymes NAD or FAD along with hydrogen protons • two forms of carbohydrate catabolism: respiration and fermentation • respiration - aerobic and anaerobic (differ in their final electron acceptor • in fermentation, NADH gives its hydrogen to an organic molecule (final elect acceptor)

  7. Respiration • Begins with glycolysis • products of glycolysis enter the Krebs cycle where molecules are oxidized to CO2 and water • NADH and FADH2 produced in glycolysis and Krebs enter the Electron Transport Chain

  8. Glycolysis • A ten step metabolic pathway that starts with 6 carbon glucose and ends with two molecules of 3 carbon pyruvic acid • Along the way: • two oxidations occur & 2 NADHs made • four ATPs made and two used up so net gain of two ATPs • Details

  9. Preparatory Stage • Between glycolysis and Krebs cycle • Each pyruvic acid is oxidized and one NADH is produced per pyruvic acid = 2 • Each pyruvic acid looses a carbon as CO2 (decarboxylation) and becomes acetyl • Coenzyme A picks up acetyl and carries it into the Krebs cycle

  10. Krebs Cycle • An eight step cyclic metabolic pathway • step 1 - Coenzyme A gives acetyl to oxaloacetic acid forming citric acid • after eight steps, oxaloacetic acid is formed again • two Krebs cycles per glucose since two pyruvic acids are formed

  11. Krebs Cycle • Summary of one Krebs cycle: • 2 decarboxylations (CO2 removed) • 1 ATP formed (substrate level phos) • 4 oxidations forming 3 NADHs and 1 • FADH2 • Per glucose: 4 CO2, 6 NADH, • 2 FADH2, 2 ATP

  12. Electron Transport Chain • A chain of seven molecules (FMN, Coenzyme Q, cytochromes) that can accept electrons (reduced) and then give up electrons (oxidized) • energy released in 3 of the transfers and is used to pump hydrogen electrons outside of plasma membrane

  13. Electrons can re-enter cell only through ATP synthetase enzyme which harnesses flowing electron energy to make 3 ATP • Oxygen atoms pick up 2 electrons and 2 hydrogen protons to form water

  14. Total ATP Count • 2 from glycolysis • 2 from the two Krebs cycles • 34 are formed by chemiosmosis in the ETC • Total = 38

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