Cellular respiration is the process by which food molecules such as glucose are oxidized to provide energy in the form of adenosine triphosphate (ATP) for use by all the energy-consuming activities carried out by the cell (Kimball, 2004). It differs from breathing in that breathing is done to saturate the blood with oxygen, which is then carried to the cells of the body where it is used for metabolic processes. Breathing is carried out for gaseous exchange; cellular respiration is carried out for energy production. Cells which respire in the presence of oxygen do so aerobically whereas those which can do it in the absence of oxygen are said to respire anaerobically. Many aerobic cells are also capable of anaerobic respiration when oxygen is temporarily deprived (Devlin, 1997).
Bimodal breathing animals - those which can breathe in air as well as in water, often use the pigment hemocyanin in water because it has a much higher affinity for oxygen, and the oxygen concentration in water is about 30 times less than that in air (Morris and Bridges, 1994). Plants respire using the pigment chlorophyll to convert carbon dioxide into oxygen. They also make glucose and oxidize it with oxygen from photosynthesis (Q201, 2004).
Glycolysis, also known as the Embden-Meyerhof pathway, is an ancient process possessed by all cells of the human body by which glucose is degraded to lactose by anaerobic fermentation (Devlin, 1997). During glycolysis, the potential energy contained in foodstuffs is released in a series of chemical reactions which occur in the cytoplasm of cells (Anderson, 1999). Some of the energy released when chemical bonds are broken in the process is used to phosphorylate ADP, and some is transferred to a coenzyme NAD+, which is later reduced to NADH. Glycolysis is a pathway by which organisms extract chemical energy from high-energy fuels in the absence of molecular oxygen (Devlin, 1997). Glycolysis can act as a...