Respiration

• Respiration


  The release of energy from food substances in living cells
• Energy release from food molecules

  1. Break down food molecules

  2. Use energy to join phosphate group to ADP to form ATP

  3. Energy stored in ATP
• ADP


  Adenosine diphosphate
• ATP


  Adenosine triphosphate
• ATP formation


  1. ADP + P + energy ® ATP

  2. ATP ← ADP + P + energy
• Uses of energy in human body

  • Muscle contraction for movement
  • Protein synthesis
  • Cell division for repair and growth
  • Active transport
  • Growth
  • Nerve impulse transmission
  • Maintaining body temperature
• Aerobic respiration


  Complete breakdown of glucose in the presence of oxygen to release large amount of energy and carbon dioxide & water as by-product
• Aerobic respiration


  Glucose + Oxygen ® Carbon Dioxide & Water
• Anaerobic respiration


  Partial breakdown of glucose in absence of oxygen to release small amount of energy; the by-product are lactic acids in Man, carbon dioxide & ethanol in plants and yeast
• Anaerobic respiration in humans

  Glucose ® Lactic acid + small amount of energy
• Anaerobic respiration in plants & yeast

  Glucose ® Carbon dioxide + Ethanol + small amount of energy
• Differences between aerobic and anaerobic respiration

  • Aerobic: Involves oxygen, large energy release, carbon dioxide & water produced
  • Anaerobic: No oxygen, small energy release, lactic acid/alcohol produced
• Oxygen debt


  During vigorous physical activities, the amount of oxygen supplied is not enough to provide energy needed by muscles cells for contracting, so cells respire anaerobically & break down glucose partially to form lactic acid
• Oxygen debt recovery


  1. Lactic acid carried in blood to liver

  2. Lactic acid broken down in liver in presence of oxygen to produce carbon dioxide & water and release ATP

  3. Heart rate and breathing rate remain high to transport lactic acid and carbon dioxide
• The extra oxygen required to break down the lactic acid is referred as oxygen debt or Excess Post-exercise Oxygen Consumption (EPOC)