Respiration is the process which involves exchange of oxygen and carbon dioxide between the organism and the environment. Respiration is the process by which chemical energy stored in the food is released in the form of ATP along with carbon dioxide and water.Respiration can be of two types – Aerobic and Anaerobic. Both of these respirations take place inside the cell.Anaerobic respiration involves the breakdown of food into alcohol and carbon dioxide in the absence of oxygen. The breakdown of glucose to release energy from the cells in anaerobic conditions is fermentation. Under anaerobic conditions prevailing in our muscle cells, the insufficiency of oxygen converts the pyruvate molecules into lactic acid and energy. Accumulation of lactic acid in our muscle cells causes cramps.
A chemical process in which energy is produced from food without using oxygen, for example by yeast

Breakdown of pyruvic acid into ethanol carbondioxide in ethanol and lactic acid un human muscles in absence of air..