respiration

• Aerobic respiration


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


  Glucose + oxygen → carbon dioxide + water (+energy)
• Anaerobic respiration


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


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

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


  Leads to muscle fatigue due to lactic acid build up
• 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


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


  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 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
• Lactic acid is transported away from muscles to the liver, where it is oxidised back to glucose
• Metabolism


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