Aerobic Respiration (WJEC GCSE Biology)

• Aerobic respiration is a process that occurs in cells when oxygen is available
• Respiration is a series of enzyme-controlled reactions within the cell, that use glucose and oxygen to release energy and produce carbon dioxide and water
• The energy transferred supplies all the energy needed for living processes to occur within cells and organisms as a whole
• Organisms need energy for:
  • Chemical reactions to build larger molecules from smaller molecules
  • Muscle contraction to allow movement
  • Keeping warm (to maintain a constant temperature suitable for enzyme activity)

Uses of energy diagram

Uses of the energy released from respiration

• The equation that summarises the chemical reactions of aerobic respiration that release energy from glucose are:

Word equation for aerobic respiration

Investigating Respiration

• We can investigate the production of  heat from respiration through experiments using germinating seeds or peas

Apparatus

• Vacuum Flasks
• Thermometer
• Cotton wool
• Germinating seeds/peas
• Dead/boiled seeds/peas

Variables

• The independent variable is the contents of the boiling tube (germinating seeds/peas or dead seeds/peas)
• The dependent variable is the change in the temperature on the thermometer after 4 days
• Control variables include
  
  • The number, age, size, species of seeds/peas
  • The starting temperature of the flasks
  • The material and size of the flasks

Method

• Rinse/wash the seeds/peas in disinfectant to kill any microorganisms on the surface of the seeds/peas which may also respire
• Set up the flasks as shown in the diagram
  • Flask A with the dead seeds/peas
  • Flask B with the germinating seeds/peas
  • Thermos flasks are used to ensure heat energy released from respiration does not dissipate into the surroundings 

• Make sure the cotton wool is plugging the top of each flask
• Hold the thermometer in place with the cotton wool
• Invert the flask
• Record the initial temperature
• After 4 days, record the final temperature

Investigating respiration diagram

Experiment to demonstrate the production of heat by living material during respiration

Results

• The thermometer in the flask with the germinating seeds/peas (flask B) should show an increase in temperature
• Flask A should remain at room temperature
• This is because the seeds/peas in flask B are respiring and releasing heat energy in the process
• This shows that respiration is an exothermic reaction
• The seeds/peas in flask A are not respiring because they are dead, so the temperature remains the same

Higher Tier Only

• The energy that is released during aerobic respiration is in the form of the molecule ATP (adenosine triphosphate)
• The quantity of ATP released in aerobic respiration is significantly more than the ATP released from anaerobic respiration
• ATP is produced in respiration in the mitochondria of cells