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AP Bio Ch. 9 Anaerobic respiration


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AP Bio Ch. 9 Anaerobic respiration

  1. 1. Anaerobic Respiration How cells make ATP in the absence of oxygen
  2. 2. Fermentation Allows Cells to Make ATP Without Using Oxygen Glucose Glycolysis Oxygen Present Citric Acid Cycle Oxidative Phosphorylation Oxygen Absent Fermentation Alcohol Lactic Acid
  3. 3. Remember…  Glycolysis happens in the cytosol  It does not require the presence of oxygen  NAD+ acts as the electron acceptor  2 ATP are generated  2 NADH are generated
  4. 4. Fermentation  An extension of glycolysis  Cells can use this step of respiration to keep up the ATP supply  But…must have a steady supply of NAD+ to act as the electron acceptor
  5. 5. •Unlike aerobic respiration, fermentation generates ATP through substrate-level phosphorylation •Fermentation can only continue if there’s a supply of the oxidizing agent NAD+ to be used in glycolysis After NADH is produced from glycolysis, its electrons are transferred to pyruvate. This regenerates the NAD+ that can again be used for another round of glycolysis.
  6. 6. In contrast…  In aerobic respiration the supply of NAD+ is continually renewed as the NADH molecules deliver their electrons to the electron transport chain
  7. 7. Fermentation  In anaerobic respiration, we need another way to recycle NAD+  Instead, the electrons in NADH are transferred to pyruvate, the end product of glycolysis
  8. 8. LE 9-18 Glucose CYTOSOL Pyruvate No O2 present Fermentation O2 present Cellular respiration MITOCHONDRION Ethanol or lactate Acetyl CoA Citric acid cycle
  9. 9. So fermentation is…  Glycolysis (2 ATP, 2 NADH, pyruvate) PLUS  Extra reactions that oxidize the NADH to NAD+ by transferring electrons to pyruvate
  10. 10. 2 main types of fermentation  Alcohol fermentation  Lactic acid fermentation
  11. 11. There Are 2 Types of Fermentation Alcohol Fermentation •Glycolysis makes pyruvate •CO2 is released from pyruvate.
  12. 12. Alcohol fermentation  Occurs in yeast and many bacteria  Pyruvate (3 carbons) converted to acetaldehyde (2 carbons) and CO2 is released (used in baking to make bread rise)  Acetaldehyde is reduced by NADH to ethanol, thus regenerating the supply of NAD+
  13. 13. Lactic Acid Fermentation  Occurs in muscle cells, some bacteria, some fungi  Pyruvate is reduced by NADH to lactic acid, thus regenerating the supply of NAD+
  14. 14. Muscle Cells  When muscles are working hard, they quickly exhaust the supply of oxygen to the cell  The cell launches into fermentation to keep up  Lactic acid accumulates in cells leading to cramps
  15. 15. Facultative Anaerobes  Organisms that can survive using either anaerobic or aerobic respiration  Yeast  Bacteria
  16. 16. Main differences between aerobic and anaerobic respiration  Aerobic Final electron acceptor - oxygen NAD+ regenerated when electrons delivered to ETC Huge energy payoff 38 ATP, glucose fully broken down through Citric Acid cycle  Anaerobic Final electron acceptor - pyruvate or acetaldehyde NAD+ regenerated when electrons given to pyruvate or acetaldehyde Less energy payoff 2 ATP, energy still trapped in pyruvate or ethanol
  17. 17. Ancient prokaryotes probably used glycolysis to make ATP What is the basis for this statement?? •The oldest prokaryotes were around before there was sufficient oxygen in the atmosphere •Glycolysis is the most widespread metabolic pathway among organisms •Glycolysis occurs in the cytosol…..prokaryotes don’t have organelles
  18. 18. Glycolysis and the Citric Acid Cycle Connect to Many Other Metabolic Pathways Many molecules aside from glucose can be used in cellular respiration to make ATP: The monomers of different molecules begin the process at different steps
  19. 19. The energy in organic molecules, which is used to power the cell, is released, but not produced during cellular respiration.