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Fermentation quiz #1

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  • What is the primary purpose of fermentation in cells, and how does it differ between humans and yeast under anaerobic conditions?
    The primary purpose of fermentation is to regenerate NAD+ so that glycolysis can continue in the absence of oxygen. In humans, anaerobic conditions lead to lactic acid fermentation, where pyruvate is reduced to lactate. In yeast, anaerobic conditions result in alcohol fermentation, where pyruvate is converted to ethanol and CO2.
  • Describe the steps involved in alcohol fermentation and lactic acid fermentation, including the fate of pyruvate and the role of NADH.
    In alcohol fermentation (yeast), pyruvate is decarboxylated to form acetaldehyde, which is then reduced by NADH to produce ethanol, regenerating NAD+. In lactic acid fermentation (humans), pyruvate is directly reduced by NADH to form lactate, also regenerating NAD+.
  • Why do red blood cells rely exclusively on lactic acid fermentation, and not alcohol fermentation?
    Red blood cells lack mitochondria and can only perform glycolysis for ATP production. They rely exclusively on lactic acid fermentation to regenerate NAD+ and sustain glycolysis, as they do not have the enzymes required for alcohol fermentation.
  • What is the main function of fermentation in cells under anaerobic conditions?
    The main function of fermentation is to regenerate NAD+ so glycolysis can continue in the absence of oxygen.
  • How does the fate of pyruvate differ between humans and yeast under anaerobic conditions?
    In humans, pyruvate is converted to lactate, while in yeast, pyruvate is converted to ethanol and CO2.
  • Describe the two main steps of alcohol fermentation in yeast.
    First, pyruvate is decarboxylated to form acetaldehyde and CO2; then, acetaldehyde is reduced by NADH to produce ethanol, regenerating NAD+.
  • What happens to pyruvate during lactic acid fermentation in humans?
    Pyruvate is directly reduced by NADH to form lactate, which regenerates NAD+.
  • Why is regenerating NAD+ important for glycolysis during fermentation?
    Regenerating NAD+ is essential because it allows glycolysis to continue producing ATP when oxygen is not available.
  • Why do red blood cells rely exclusively on lactic acid fermentation?
    Red blood cells lack mitochondria and can only perform glycolysis for ATP, so they use lactic acid fermentation to regenerate NAD+ and sustain glycolysis.
  • What would happen if cells could not regenerate NAD+ during anaerobic conditions?
    If cells could not regenerate NAD+, glycolysis would stop because NAD+ is required for its reactions, leading to a lack of ATP production under anaerobic conditions.