Respiration
Cells require energy for activities such as growth and cell division. In animals, muscle cells require energy for contracting and nerve cells require energy for transmitting nerve impulses.
The energy is supplied by food that the cells take in.
The break down of food to release energy is called The chemical change that takes place inside living cells, which uses glucose and oxygen to release the energy that organisms need to live. Carbon dioxide is a by-product of respiration.. The main food used by cells for respiration is glucose.
If oxygen is present then animal, plant and yeast cells can carry out With oxygen. respiration. The overall process of aerobic respiration is illustrated above.
If oxygen is absent then respiration can still take place. Animal, plant and yeast cells complete the breakdown of food by carrying out fermentation.