Respiration is the process in which nutrients are converted into useful energy in a cell. During respiration, energy is released in a form that can be used by cells. All living things respire. Both plant and animal cells use the process of respiration to release energy from glucose.
There are two types of respiration. One is aerobic respiration and the other is anaerobic respiration. Aerobic respiration occurs in the presence of oxygen. Here, oxygen is utilized to break down food (glucose) to release high amounts of energy. Anaerobic respiration occurs in the absence of oxygen. During respiration in yeast and bacteria, oxygen is not involved in the oxidation of food. Food (glucose) is broken down into ethyl alcohol and carbon dioxide this is called anaerobic respiration.
- Animals obtain carbohydrates, such as starch and sugars, by eating them. Some heat is released by these chemical reactions in cells, and it is this we experience as body heat.
- Plants make their own carbohydrates during photosynthesis. They get carbon dioxide from the environment and their energy from the sun.
Some use oxygen to break down glucose completely into CO2 (Carbon dioxide) and H2O (Water).
See these (in this order) for an outline of the biochemistry of aerobic respiration: