2.2 Respiration

What is Respiration?

Respiration in living  organisms is the series of chemical changes which release energy from food material. 
it involves a complicated chain of chemical breakdowns, accelerated by enzymes, but it can be regarded, for experimental purposes, as the breakdown of carbohydrates to form carbon dioxide and water, with a corresponding release of energy. 

Cellular respiration takes place all the time in the cells of living things. There are two types of respiration: 

• Aerobic respiration - Requires oxygen to fully oxidize the organic molecule. This releases lots of energy.
• Anaerobic respiration -The breakdown of the molecule without oxygen. This releases much less energy.

Aerobic Respiration

Aerobic respiration is the release of energy from glucose or another organic substrate in the presence of Oxygen. Strictly speaking aerobic means in air, but it is the Oxygen in the air which is necessary for aerobic respiration. Anaerobic respiration is in the absence of air.

Here is a molecular model of a glucose molecule.

Anaerobic Respiration

Anaerobic respiration is a type of respiration that does not use oxygen. It is used when there is not enough oxygen for aerobic respiration. It can be summarised by the following equation:

glucose → lactic acid (+ energy released)

This type of respiration may be used when, for example, an animal is being chased by a predator.

Anaerobic respiration also takes place in plants and some microbial cells in the presence of little or no oxygen. Examples of this include the roots of plants in waterlogged soils and bacteria in puncture wounds.

Anaerobic respiration in plant cells and some microorganisms (such as yeast) produces ethanol and carbon dioxide, as opposed to lactic acid. It can be summarised by the following equation:

glucose → ethanol + carbon dioxide (+ energy released) 

Please click link below for more information 

http://www.diffen.com/difference/Aerobic_Respiration_vs_Anaerobic_Respiration