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How Cells Make ATP

Explore the intricacies of cellular respiration, including aerobic and anaerobic processes, glycolysis, citric acid cycle, electron transport chain, and ATP synthesis. Learn how cells generate energy from glucose in a detailed and insightful manner.

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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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