Respiration

• Aerobic respiration

  An exothermic reaction in which glucose reacts with oxygen to release energy which can be used by cells
• Aerobic respiration equations

  1. Glucose + oxygen → carbon dioxide + water (+energy)

  2. C6H12O6 + 6O2 → 6CO2 + 6H2O (+energy)
• Where aerobic respiration takes place

  In the mitochondria
• Why organisms require the energy released by respiration

  • Synthesis of larger molecules
  • Muscle contraction
  • Maintenance of body temperature
  • Active transport
• Anaerobic respiration

  An exothermic reaction in which glucose is broken down to release energy in the absence of oxygen
• Anaerobic respiration equation

  Glucose → lactic acid (+energy)
• Why anaerobic respiration is less efficient than aerobic respiration

  Glucose is not completely broken down, so less energy is transferred
• Anaerobic respiration

  Can lead to muscle fatigue due to lactic acid build up in muscles, preventing efficient contraction
• Oxygen debt

  The amount of oxygen needed to convert lactic acid into back into glucose after anaerobic respiration
• Fermentation

  A type of anaerobic respiration that occurs in yeast cells
• Fermentation equation

  Glucose → ethanol + carbon dioxide (+energy)
• Importance of fermentation

  It is used in the production of bread and alcoholic drinks
• Differences between aerobic and anaerobic respiration

  • Aerobic requires oxygen; anaerobic does not
  • Aerobic produces CO2 and water; anaerobic produces lactic acid or ethanol + CO2
  • Aerobic transfers a greater amount of energy
• How muscles store glucose

  As glycogen
• Changes in the body when muscular activity increases

  1. Heart rate increases and arteries dilate - increases flow of oxygenated blood to muscles

  2. Breathing rate increases and breathing is deeper - increases the rate of gaseous exchange

  3. Stored glycogen is converted back into glucose
• How lactic acid is transported away from the muscles (higher)
• Metabolism

  The sum of all the reactions that take place in a cell or an organism
• How cells use the energy transferred by respiration


  To continuously carry out enzyme-controlled processes which lead to the synthesis of new molecules
• Examples of metabolic reactions

  • Glucose into starch/glycogen/cellulose
  • Glycerol and fatty acids into lipids
  • Glucose and nitrate ions into amino acids
  • Photosynthesis
  • Respiration
  • Breakdown of excess proteins into urea