Enzymes and respiration

Enzymes in cells catalyse photosynthesis, protein synthesis - joining amino acids together, and aerobic respiration.

Aerobic respiration

Respiration is not the same thing as breathing. That is more properly called ventilation. Instead, respiration is a chemical process in which energy is released from food substances, such as glucose - a sugar.

Aerobic [Aerobic: 'With oxygen.' Aerobic exercise involves oxygen consumption by the body. If exercise is not too fast and is steady, the heart can supply all the oxygen the muscles need. ] respiration needs oxygen to work. Most of the chemical reactions involved in the process happen in tiny objects inside the cell cytoplasm, called mitochondria [mitochondria: structures in the cytoplasm of all cells where respiration takes place. Singular is mitochondrion ].

This is the equation for aerobic respiration:

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

The energy released by respiration is used to make large molecules from smaller ones. In plants, for example, sugars, nitrates and other nutrients are converted into amino acids. Amino acids can then join together to make proteins. The energy is also used:

• to allow muscles to contract in animals
• to maintain a constant body temperature in birds and mammals

You may wish to check your understanding of how respiration affects the length of food chains, and the efficiency of food production. Visit the Food chains and cycles section for a reminder.