2.33 – Understand that the process of respiration releases energy in living organisms.
– Respiration is a process that breaks down glucose to release energy in the form of
2.34 – Describe the differences between aerobic and anaerobic respiration.

Aerobic Anaerobic
Energy Released 38ATP 2ATP
Oxygen Yes No
Waste Carbon Dioxide + Water Lactic Acid

2.35 – Write the word equation and the balanced chemical symbol equation for aerobic
respiration in living organisms.
Glucose + Oxygen → Carbon Dioxide + Water
C6H12O6 + 6O2 → 6CO2 + 6H2O

2.36 – Write the word equation for anaerobic respiration in plants and in animals.
Glucose → Lactic Acid
(C6H12O6 → 2C3H6O3)
Glucose → Ethanol + Carbon Dioxide
(C6H12O6 → 2C2H5OH + 2CO2)
2.37 – Describe experiments to investigate the evolution of carbon dioxide and
heat from respiring seeds or other suitable living organisms.
– Hydrogencarbonate indicator solution is orange, and turns yellow if carbon dioxide is
added to it.
– Small organisms (e.g. maggots and woodlice) are placed in a boiling tube on a gauze
• This keeps the organisms supported and away from the chemical at the same time.
– Observe any colour changes over a period of time.

– The experiment is repeated with a different organism.
– Some peas are soaked in water for 24 hours so that they start to germinate. A second
batch of peas is boiled to kill them (it acts as the control experiment).
– Each set of peas is washed in a 1% bleach solution, which acts as a disinfectant,
surface-sterilising them and killing any micro-organisms present.
– The peas are rinsed twice to ensure no bleach is left.
– Each batch of peas is placed in an inverted vacuum flask, leaving some air in each
• The vacuum flask insulates its contents so that any small changes in temperature
can be measured (with a thermometer).
– The seeds produce carbon dioxide gas which is denser than air.
• The inverted flasks and cotton wool allow it to escape.
– The apparatus is left for a couple of days, and the temperature inside each flask is
measured at the end of the experiment.
– The results should show that the temperature of the flask with the dead peas stayed
constant, and the temperature of the flask with the living peas increased