Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!
Print

Science

Fitness and respiration

Respiration

Respiration is the process by which energy is released from glucose.

Aerobic respiration

Aerobic respiration requires oxygen. It happens in cells when glucose reacts with oxygen. Here are the word and symbol - higher only - equations:

glucose + oxygen    →    carbon dioxide + water (+ energy)

C6H12O6 + 6O2    →    6CO2 + 6H2O (+ energy)

Energy is shown in brackets in each equation because it is not a chemical substance.

Anaerobic respiration

Anaerobic respiration does not need oxygen. It happens when there is not enough oxygen for aerobic respiration. Here is the word equation:

glucose    →    lactic acid (+ energy)

Much less energy is released by anaerobic respiration than by aerobic respiration.

Back to Understanding ourselves index

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.