Anaerobic respiration

• All of anaerobic respiration occurs in the cytoplasm
• Lactate

  Same as lactic acid except a hydrogen missing from the carboxylic acid part
• Anaerobic respiration step 2a: In animals

  1. Pyruvate + H → Lactate, hydrogen provided by NADH from glycolysis and reform NAD to again be used in glycolysis

  2. Pyruvate reduced

  3. NADH is oxidised
• Anaerobic respiration step 2b: In plants and some microorganisms

  Pyruvate + H → Ethanol + $CO_2$, H provided by NADH and NAD is reformed to be reused
• Even though in high concentration lactate and ethanol are harmful, they ensure glycolysis can continue to produce the small amount of ATP and produce molecules that can be used in Aerobic respiration once oxygen becomes available
• Respiratory substrates in order of energy released

  • Lipids
  • Proteins
  • Carbohydrates
• Reason for order of energy released

  Based on how many hydrogen atoms are released to bind to NAD and FAD to produce their reduced version to donate to the electron transfer chain for the oxidative phosphorylation of ATP
• Respiratory quotient (RQ)

  Ratio of carbon dioxide produced to oxygen used
• RQ values for different respiratory substrates

  • Carbohydrates: 1
  • Proteins: 0.9
  • Lipids: 0.7
• Proteins and lipids take more oxygen to break down
• The reason why RQ values are different is based on the proportion of C-H bonds present in the molecule which requires more oxygen to break
• A respirometer is used to find the RQ value
• in regards the respiratory quotient graph it will slowly decline and then sharply rise up as anaerobic oxygen does not consume any oxygen and produces co2