Why Do Livings Respire?

• Respiration


  • Respiration is the breaking down of food molecules such as glucose to release energy
  • Respiration occurs in the mitochondria
  • Two types of respiration :

  1. Aerobic
  2. Anaerobic
• Aerobic Respiration


  • Aerobic respiration involves the breakdown of glucose in the presence of oxygen

  • produces carbon dioxide and water as waste products

  • generates large amount of energy (including heat energy)

  •C6H12O6 + 6O2 → 6CO2 + 6H2O (glucose + oxygen -> carbon dioxide + water)
• Anaerobic Respiration


  • Anaerobic respiration involves the breakdown of glucose in the absence of oxygen

  • generates relatively small amount of energy

  • C6H12O6 -> 2C3H6O3 (Glucose -> Lactic acid)

  • Anaerobic respiration occurs in muscle cells during vigorous activity.
• What Happens During Vigorous Activity?

  • Aerobic respiration in muscle cells increased.

  • increased breathing to obtain oxygen

  • increased heart rate to supply oxygen

  • When continuous muscle contractions occurs, muscle cells need more energy to contract

  • Aerobic respiration alone is not fast enough to supply the increased in energy demand

  • Anaerobic respiration takes place to meet the increased energy demand.

  • Muscles are said to incur what is called an oxygen debt
• Oxygen Debt


  • Oxygen is the amount of oxygen debt to remove the build up of lactic acid from the body
  • Oxygen debt is addressed through increased heart rate, and deeper and faster breathing which continue for a while after the vigorous activity has stopped
  • Fast heart rate increases rate of transport of lactic acid to liver via blood for removal, and increases rate of transport of oxygen to liver
  • Continued deeper and faster breathing allows body to obtain more oxygen for supply to liver