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Chapter 9

Chapter 9. Biology Sixth Edition Raven/Johnson (c) The McGraw-Hill Companies, Inc. Drives ATP synthesis. Cellular respiration is the step-wise release of energy from molecules (usually carbohydrates) used to synthesize ATP molecules.

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Chapter 9

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  1. Chapter 9 Biology Sixth Edition Raven/Johnson (c) The McGraw-Hill Companies, Inc.

  2. Drives ATP synthesis Cellular respiration is the step-wise release of energy from molecules (usually carbohydrates) used to synthesize ATP molecules. Oxidation of glucose is an exergonic reaction (releases energy) which drives ATP synthesis - an endergonic reaction (energy is required). Overall reaction for cellular respiration:

  3. NAD+ and FAD • Each step of cellular respiration requires a separate enzyme • Some enzymes use the oxidation-reduction coenzyme NAD+ or the coenzyme FAD.

  4. The NAD+ cycle Remember: When NAD+ NADH it has been reduced. Remember: When NADHNAD+ it has been oxidized.

  5. 4 Phases of Complete Glucose Breakdown • Glycolysis - yields 2 ATP • Pyruvate oxidation – oxidation reaction • Krebs cycle –yields 2 ATP • Electron transport chain – yields 32-34 ATP • Net ATP produced from respiration: 36-38

  6. Outside the Mitochondria: Glycolysis Universally found in all organisms. Does not require oxygen.

  7. Overview of Glycolysis Glucose (6-C sugar) 2 ATP 2 ADP 6-C sugar diphosphate 3-C sugar-phosphate 3-C sugar-phosphate 2 ADP 2 ADP 2 ATP 2 ATP 2 NAD+ 2 NAD+ 2 NADH 2 NADH 3-C pyruvate 3-C pyruvate

  8. Glycolysis summary Inputs: Glucose 2 NAD+ 2 ATP 4 ADP + 4 P Outputs: 2 pyruvate 2 NADH 2 ADP 4 ATP (2 net gain)

  9. Fermentation inputs and outputs per glucose molecule Inputs: glucose 2 ATP 4 ADP + 4 P Outputs: 2 lactate or 2 alcohol and 2 CO2 2 ADP 4 ATP (2 net gain) Pyruvate (Oxygen present) (Oxygen not present) Cellular Respiration Fermentation

  10. 2-carbon molecule + 1 CO2 3-carbon molecule + 0 CO2

  11. 2 NAD+ 2 NADH + H+ 2Pyruvate + 2CoA 2 Acetyl-CoA + 2CO2 Pyruvate oxidation: if oxygen is present Pyruvate is converted to a C2acetyl group attached to coenzyme A (CoA), and CO2is released. This occurs in the cytoplasm if oxygen is present.

  12. Krebs Cycle • The Krebs cycle is a cyclical metabolic pathway located in the matrix of the mitochondria. • At the start of the citric acid cycle, CoA carries the C2 acetyl group to join a C4 molecule, and C6citrate results.

  13. Acetyl-CoA (2 C) NAD+ C6 NADH C4 CO2 NADH NAD+ C5 Krebs cycle FADH2 NAD+ FADH NADH C4 CO2 ATP ADP + P

  14. Krebs cycle inputs and outputs per glucose molecule Inputs: 2 acetyl groups 6 NAD+ 2 FAD 2 ADP + 2 P Outputs: 4 CO2 6 NADH 2 FADH2 2 ATP

  15. Electron Transport Chain • The electron transport chain located in the cristae of mitochondria is a series of protein carriers • Electrons carried by NADH and FADH2 enter the electron transport chain. • As a pair of electrons is passed from carrier to carrier, energy is released and is used to form ATP molecules by oxidative phosphorylation.

  16. Oxygen receives energy-spent electrons at the end of the electron transport system then combines with hydrogen to form water: ½ O2 + 2 e- + 2 H+→ H2O

  17. Glucose + O2 CO2 + H2O + ATP

  18. Glycolysis Transition Reaction Krebs Cycle NAD+ Electron Transport Chain NADH Remember: Electrons = Energy

  19. Feedback mechanisms

  20. Acidic group H group Amino group R-group

  21. With Beta-oxidation the last two carbons of a fatty acid chain enter the Krebs cycle. This process is repetitive until the entire fatty acid chain is consumed. A 6 Carbon fatty acid molecule produces more ATP than a glucose (based on the amount of NADH and FADH2 produced.

  22. When PEP transfers a phosphate group to ADP, pyruvate is formed. This is called substrate level phosphorylation.

  23. ADP and PEP are substrates and an enzyme facilitates the transfer of a phosphate group from PEP to ADP to create ATP. The energy in the bond is conserved.

  24. The End.

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