Aerobic and anaerobic respiration: The energy transferred supplies all the energy needed for living processes.

The idea

Respiration is a series of enzyme-controlled reactions that transfers chemical energy from glucose into a usable form in cells. This transferred energy powers every living process: muscle contraction for movement, active transport of ions such as Na⁺ across membranes, protein synthesis from amino acids, cell division, and maintaining a constant body temperature in mammals and birds. The energy is not created; it is transferred from the bonds of glucose to ATP, the cell's immediate energy currency. For example, a runner's leg muscles use this energy for contraction, while root hair cells use it for active transport of mineral ions. Without a continuous energy supply, cells cannot carry out these processes and the organism dies.

What earns the marks

• Respiration transfers energy from glucose rather than creating new energy, because energy cannot be created or destroyed.
• The transferred energy is used for muscle contraction, active transport, protein synthesis, cell division and temperature maintenance.
• Energy is transferred in controlled steps by enzymes, releasing it gradually rather than in one damaging burst.
• ATP acts as the immediate energy currency that links respiration to cellular processes.
• All living cells, including plant, animal, fungal and bacterial cells, carry out respiration continuously.

Common mistakes and how to put them right

• Saying respiration 'makes energy' rather than transfers it from glucose.

  Put it right by writing that energy is transferred from glucose to ATP.

• Confusing respiration with breathing.

  Put it right by stating that breathing is ventilation of the lungs, whereas respiration is a chemical process in cells.

• Believing plants photosynthesise instead of respiring.

  Put it right by stating that plants respire continuously and also photosynthesise in light.

Exam tips

• Link each named living process to respiration explicitly, for example 'active transport of Na⁺ requires energy transferred by respiration'.
• Use the phrase 'energy is transferred' rather than 'energy is produced' to match the specification wording.
• When asked why an organism dies without respiration, refer to the loss of energy supply for processes such as active transport and protein synthesis.