Respiration using oxygen to break down food molecules is called aerobic respiration. Glucose is the molecule normally used for respiration – it is the main respiratory substrate. Glucose is oxidised to release its energy.
The word equation for aerobic respiration is:
glucose + oxygen → carbon dioxide + water + energy released
The reactants in this reaction are glucose and oxygen. The products are carbon dioxide and water.
You need to be able to recognise the chemical symbols:
C6H12O6 + 6O2 → 6CO2 + 6H2O
Respiration is a series of reactions, but this summarises the overall process.
The first stages of respiration occur in the cytoplasm of cells, but most of the energy released is in the mitochondria.