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Chapter 8.5

Chapter 8.5. Anaerobic Energy-Releasing Pathways. AP Biology Fall 2010. Anaerobic Pathways. Anaerobic pathways operate when oxygen is absent (or limited) Pyruvate from glycolysis is metabolized to produce molecules other than acetyl-CoA. Fermentation pathways.

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Chapter 8.5

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  1. Chapter 8.5 Anaerobic Energy-Releasing Pathways AP Biology Fall 2010

  2. Anaerobic Pathways • Anaerobic pathways operate when oxygen is absent (or limited) • Pyruvate from glycolysis is metabolized to produce molecules other than acetyl-CoA

  3. Fermentation pathways • Organisms that carry out fermentation (fermentors) are diverse • Many die when exposed to oxygen • Others use oxygen but switch when it becomes scarce • Fermentation yields enough energy for many single-celled anaerobic organisms • Sufficient for some aerobic cells when oxygen levels drop • Insufficient for large, multi-celled organisms Lactose fermenting bacteria turn bright pink!

  4. Alcoholic Fermentation • Fermentation begins with glucose degradation to pyruvate • Cellular enzymes convert pyruvate to acetaldehyde, which then accepts electrons from NADH to become alcohol

  5. Alcoholic Fermentation • Yeasts are valuable in the backing industry and in alcoholic beverage production • Carbon dioxide by-product makes dough “rise”

  6. Lactate fermentation • Certain bacteria (as in milk) and muscle cells have the enzymes capable of converting pyruvate to lactate • No additional ATP beyond the net two from glycolysis is produced • NAD+ is regenerated

  7. The twitchers • When muscle cells are very active, they convert to producing lactate temporarily • Slow stitch muscle fibers (dark red) • Support steady, prolonged activity because they have many mitochondria making large quantities of ATP • Fast twitch muscle fibers (light colour) have few mitochondria and produce small amounts of ATP by lactate fermentation • Supporting quick, non-sustained demands for energy

  8. Review • T/F Yeast is used in bread making because it produces carbon dioxide • T/F In lactate fermentation FAD is regenerated • T/F Fast twitch muscles are dark red and support steady, prolonged material

  9. answers • True • False NAD+ is regenerated • False This describes slow twitch muscles

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