Anaerobic Respiration and Fermentation

• Cells generate ATP through glycolysis, the citric acid cycle, and oxidative phosphorylation
• Oxygen is crucial for this process, hence the term "aerobic" respiration.
• Aerobic Respiration and Fermentation

  Both processes do not rely on oxygen and are used by certain microorganisms and during strenuous activity in animals.
• Anaerobic respiration uses an electron transport chain with a different final electron acceptor (e.g., sulfate ion).
• Anaerobic respiration

  Uses an electron transport chain with non-oxygen electron acceptors.
• Fermentation with glycolysis, which does not require oxygen.
• fermentation

  Results in 2 ATP per glucose molecule.
• Pyruvate does not enter the citric acid cycle but undergoes different processes depending on the fermentation type.
• Regenerates NAD+ allowing glycolysis to continue.
• Alcohol Fermentation

  o Glucose oxidized to pyruvate.

  o Pyruvate undergoes decarboxylation to acetaldehyde.

  o Acetaldehyde is reduced to ethanol by NADH, regenerating NAD+.

  o Utilized by yeast to produce alcohol and carbon dioxide (used in brewing and baking).
• Lactic Acid Fermentation

  o Pyruvate is directly reduced by NADH to lactate, regenerating NAD+.

  o No carbon dioxide release.

  o Used by certain fungi and bacteria (e.g., in cheese and yogurt production).

  o Occurs in human muscle cells during low oxygen supply, causing muscle fatigue.
• All begin with glycolysis, an ancient method of ATP production.
• Early prokaryotic life utilized glycolysis before the presence of oxygen in Earth's atmosphere.
• Fermentation: Reduction of pyruvate (lactic acid fermentation) or acetaldehyde (alcohol fermentation).
• Aerobic Respiration: Citric acid cycle and electron transport chain with oxygen.
• Anaerobic Respiration: Electron transport chain with non oxygen electron acceptors.
• Glycolysis produces NADH, which must be oxidized to regenerate NAD+.
• NADH is oxidized by reacting with pyruvate or acetaldehyde during fermentation or by dumping electrons into the electron transport chain during respiration
• Oxidative phosphorylation (electron transport chain) produces most of the ATP (30-32 ATP).
• Fermentation produces only 2 ATP (from glycolysis alone).