Anaerobic respiration

Differences between aerobic and anaerobic respiration

  • some steps of aerobic respiration occurs in the mitochondria while anaerobic respiration happens wholly in the cytoplasm

  • only aerobic includes the link reaction, Krebs, and oxidative phosphorylation

  • aerobic yields approx 34 ATP per glucose molecule while anaerobic yields only 2 ATP per glucose molecule

Categories of organisms based on their oxygen needs

  • obligate anaerobes

    • cannot survive in the presence of oxygen

  • facultative anaerobes

    • switch between aerobic and anaerobic depending on oxygen availability

  • obligate aerobes

    • depend on oxygen to synthesise ATP

  • eukaryotic cells can perform either type of respiration

    • situationally dependent

Anaerobic processes

  • in anaerobic conditions cells can produce a small yield of ATP through glycolysis

    • can only continue if the reduced NAD that is produced can be oxidised again

  • the link reaction and Krebs cycle cannot continue of all of the FAD and NAD is reduced because they cannot accept any more protos and electrons

  • oxidative phosphorylation cannot occur without oxygen as the final electron acceptor

Alcohol fermentation

  • occurs in yeasts and some plants

  • pyruvate loses a molecule of CO2 and is converted into ethanal

  • ethanal accepts a hydrogen from reduced NAD

  • produces ethanol and regenerates NAD

  • ethanol cannot be further metabolised and must be removed as a waste product

Lactic acid fermentation

  • occurs in some animals and bacteria

  • pyruvate accepts a hydrogen from reduced NAD

    • catalysed by lactate dehydrogenase

  • forms lactic acid and regenerates NAD

  • lactic acid can be oxidised back to pyruvate to generate more ATP or it can be stored as glycogen

  • if too much anaerobic respiration occurs in muscle tissue:

    • the reduced quantity of ATP produced is insufficient to maintain vital processes for extended time periods

    • lactic acid accumulates and causes:

      • cramp

      • muscle fatigue

      • reduces pH affecting enzymes