Types of respiration

• All living cells respire to release energy
• Organisms need energy for everything they do (for example, making new substances, moving)
• Aerobic respiration


  A series of chemical reactions that can be summarised as: glucose + oxygen → carbon dioxide + water
• Energy is released in aerobic respiration but is not a chemical substance and so is not shown in the word equation
• Carbon dioxide detection


  • Limewater (which turns cloudy)
  • An indicator (such as hydrogen carbonate) because it is acidic
• Anaerobic respiration


  Does not require oxygen
• Anaerobic respiration in humans is used to release energy from glucose when more energy is needed than can be supplied by aerobic respiration (for example, during strenuous exercise)
• Products of anaerobic respiration

  • Glucose
  • Lactic acid
• Anaerobic respiration causes muscles to tire quickly and so cannot be used for extended periods
• A lot of the lactic acid travels from the muscles to the liver, where it is converted back to glucose
• Anaerobic respiration releases less energy than aerobic respiration
• After strenuous exercise, the body needs extra oxygen
• EPOC


  Excess post-exercise oxygen consumption (or 'oxygen debt')
• EPOC replaces oxygen lost from oxygen stores (in the blood and in muscles) and provides oxygen for increased levels of aerobic respiration (for example, to provide energy for removing lactic acid, for faster breathing, for faster heart rate)
• Oxygen demand during exercise

  Greater than supply
• Different organisms use different organs for gas exchange

  • Stomata in leaves (plants)
  • Gills (e.g. fish)
  • Skin (e.g. frogs)
  • Trachea (windpipe)
  • Lungs
• Each air sac contains many alveoli which give the lungs a huge surface area
• This huge surface area ensures that diffusion happens quickly
• Capillaries


  Have walls that are only one cell thick, to speed up diffusion
• Oxygen is carried by haemoglobin in red blood cells
• Carbon dioxide (and glucose) are dissolved in the plasma