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Energy Production

Learn about the essential processes of oxidation, reduction, phosphorylation, and carbohydrate catabolism in cellular energy production. Discover the detailed pathways of glycolysis, Krebs cycle, and the Electron Transport Chain.

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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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