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How Cells Make ATP

How Cells Make ATP. Chapter 7. Cellular Respiration. Aerobic respiration: Releases the energy in glucose in a steady fashion Requires molecular oxygen Includes redox reactions Anaerobic respiration Anaerobic respiration and fermentation Does not require oxygen All exergonic.

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How Cells Make ATP

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  1. How Cells Make ATP Chapter 7

  2. Cellular Respiration • Aerobic respiration: • Releases the energy in glucose in a steady fashion • Requires molecular oxygen • Includes redox reactions • Anaerobic respiration • Anaerobic respiration and fermentation • Does not require oxygen • All exergonic

  3. Aerobic respiration • Four stages: • Glycolysis – in the cytosol • Formation of acetyl CoA • Citric acid cycle in mitochondria • Electron transport/chemiosmosis

  4. Figure 7-2 p. 139

  5. Glycolysis • ‘sugar splitting’ • Does not require oxygen • Two major phases: • Energy investment phase (endergonic) • Energy capture phase (exergonic) • Each glucose molecule is converted to 2 pyruvate molecules and 2 NADH and 2 ATP

  6. Formation of acetyl CoA • Pyruvate molecules (from glycolysis): • 1st carboxyl group is split off as CO2 • Remaining 2-carbon fragment is oxidized and e- transferred to NAD+ • The oxidized 2-carbon fragment is attached to coenzyme A  acetyl CoA

  7. Citric acid cycle (aka Krebs Cycle): • For every glucose molecule from glycolysis, 2 acetyl groups enter • Each 2-C acetyl group combines with a 4-C compound • 2 CO2 molecules are removed from each • 1 ATP, 3 NADH, 1 FADH2 per acetyl group – the energy here will be use to synthesize more ATP in the next phase

  8. Figure 7-6 p. 144

  9. Electron transport chain • A series of electron carriers in the mitochondrial membrane • Electrons pass down in a series of redox reactions • e- lose energy as they pass along the chain • This energy allows the cell to move H+ to the intermembrane space and create a proton gradient (chemiosmosis) • The H+ protons can only move back into the matrix through ATP synthase  this provides the energy for converting ADP + Pi to ATP

  10. Figure 7-9 p. 148

  11. Figure 7-10 p. 149

  12. Oxidative phosphorylation Substrate-level phosphorylation Figure 7-11Page 150 Glycolysis Glucose 2 NADH 4 – 6 ATP 2 ATP Pyruvate Acetyl coenzyme A 2 NADH 6 ATP 6 NADH 18 ATP Citric acid cycle 2 ATP 2 FADH2 4 ATP Electron transport and chemiosmosis 32 - 34 ATP Total ATP from oxidative phosphorylation

  13. Alternative pathways • Many organisms depend on nutrients other than glucose • Products of protein and lipid catabolism enter the same pathways as glucose

  14. Anaerobic respiration • Electrons transferred from fuel molecules to the electron transport chain • The final electron acceptor is an inorganic substance such as nitrate (for the nitrogen cycle) or sulfate

  15. Fermentation • Also anaerobic • But does not use an electron transport chain • Electrons are transferred to an organic molecule • This process produces either alcohol or lactate

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