Respiration

Glucose is a store of chemical energy. When glucose is broken down into simpler chemicals the energy is released and the cell can use it for such things as movement, growth and warmth. To get the maximum energy out of glucose it is best to react it with oxygen to produce carbon dioxide and water. This is called Aerobic respiration.

Aerobic respiration

Glucose + Oxygen ----Carbon dioxide + Water + released energy

For short spells it is possible for human cells to respire without any oxygen. For instance, when an athlete runs 100m there is no time for the body to get enough oxygen to all of the muscles. In this case the cells do anaerobic respiration, which is respiration without oxygen. The cells convert the glucose into lactic acid and a small amount of energy is released. Lactic acid is harmful in the body, so humans cannot respire this way for very long. Afterwards the lactic acid needs to be removed and this requires oxygen (it is known as the oxygen dept). This is why an athlete pants after a race.

Respiration is one of the characteristics of living things. If a cell does not respire then it is not alive. Therefore, plant cells respire and animal cells respire and so do bacteria cells and fungi cells.