Aerobic and Anaerobic Respiration

• Aerobic respiration


  Respiration using oxygen, the most efficient way to transfer energy from glucose
• Aerobic respiration


  • Happens all the time in plants and animals
  • Most of the reactions happen inside mitochondria
• Aerobic respiration


  Glucose + oxygen → carbon dioxide + water
• Anaerobic respiration


  Respiration without oxygen, the incomplete breakdown of glucose, making lactic acid
• Anaerobic respiration in muscle cells

  Glucose → lactic acid
• Anaerobic respiration does not transfer nearly as much energy as aerobic respiration because glucose isn't fully oxidised
• Anaerobic respiration is only useful in emergencies, e.g. during exercise when it allows you to keep on using your muscles for a while longer
• Anaerobic respiration in plants and yeast

  Produces ethanol and carbon dioxide instead of lactic acid
• Anaerobic respiration in plants and yeast

  Glucose → ethanol + carbon dioxide
• Anaerobic respiration in yeast cells is called fermentation
• Fermentation by yeast is used to make bread and alcoholic drinks
• In bread-making, the carbon dioxide from fermentation makes bread rise
• In beer and wine-making, the fermentation process produces alcohol
• When you exercise


  Your muscles need more energy from respiration to contract
• When you exercise


  Your breathing rate and breath volume increase to get more oxygen into the blood, and your heart rate increases to get this oxygenated blood around the body faster
• When you do really vigorous exercise

  Your body can't supply oxygen to your muscles quickly enough, so they start respiring anaerobically
• Anaerobic respiration leads to lactic acid build-up in the muscles, which gets painful
• Long periods of exercise cause muscle fatigue - the muscles get tired and then stop contracting efficiently
• Oxygen debt


  The amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from the cells
• After anaerobic respiration


  You have an oxygen debt and have to keep breathing hard for a while after you stop to get more oxygen into your blood
• Your body also transports the lactic acid to the liver, where it is converted back to glucose
• Investigating the effect of exercise on the body

  1. Measure breathing rate by counting breaths

  2. Measure heart rate by taking the pulse
• Measuring pulse rate


  • After sitting down for 5 minutes
  • After 5 minutes of gentle walking
  • After 5 minutes of slow jogging
  • After running for 5 minutes
• Pulse rate increases the more intense the exercise is, as your body needs to get more oxygen to the muscles and take more carbon dioxide away from the muscles
• To reduce the effect of any random errors, do the exercise investigation as a group and plot the average pulse rate for each exercise