Aerobic and Anaerobic Respiration

Cellular respiration is an exothermic reaction that takes place in all living cells and supplies all the energy needed for living processes. Respiration in cells can take place in the presence of oxygen, aerobically or in the absence of oxygen, anaerobically. Organisms need energy for chemical reactions to build larger molecules, for movement and to maintain a constant internal environment and temperature.  All living cells respire including plants. Plants use the glucose they produce to make energy for their cells in order to support growth.

Aerobic respiration is the primary type of respiration that takes place inside animal cells.  Aerobic respiration coverts glucose and oxygen into carbon dioxide and water. The reaction for aerobic respiration is the reverse of the reaction for photosynthesis so if you know one, you know the other.

You need to know both the word equation and the chemical equation for your exam. This reaction takes place in the mitochondria of the cell.

Anaerobic respiration is different. In anaerobic respiration there is no oxygen present. In humans glucose gets converted to lactic acid in muscle cells.

As the oxidation of glucose is incomplete, anaerobic respiration releases much less energy when compared to that of aerobic respiration. Anaerobic respiration is used for short intense bursts of exercise such as sprinting. The energy is required at high levels for a short time. The lactic acid that builds up as a result of anaerobic respiration in humans results in cramps and muscle fatigue. This lactic acid can be removed and degraded by reacting it with oxygen in the liver.

Anaerobic respiration in plants and yeast is slightly different to that found in humans. In anaerobic respiration in plants and yeast, glucose is converted into ethanol and carbon dioxide.

Anaerobic respiration in yeast cells is called fermentation and is an important economic process in the manufacturing of bread and alcoholic drinks. In bread making it causes the bread to rise and in beer and wine making it produces alcohol.