The definition of respiration according to 'Biochemistry fifth edition' written by Berg, Tymoczko and Stryer' is:
"An ATP-generating process in which an inorganic compound (such as molecular oxygen) serves as the ultimate electron acceptor. The electron donor can be either an organic compound or an inorganic one".
Adenosine triphosphate (ATP) is the 'Eneryg currency of the cell', hence energy is produced through respiration.
The first metabolic pathway involved in the production of ATP is glycolysis which is anaerobic. The sequence of reactions in glycolysis metabolise one molecule of glucose to two molecules of pyruvate and produce a net amount of two molecules of ATP. This is in an individual cell, but if we think about a muscle as a collection of cells we can understand that this process would be used in anaerobic exercise (when no oxygen is available). When oxygen is available however, the yield of ATP generated increases dramatically. The aerobic processing of glucose starts with the complete oxidation of glucose derivatives to carbon dioxide. This oxidation takes place in the citric acid cycle, also known as the Krebs cycle (after Hans Krebs), or the tricarboxylic acid cycle. The diagram below shows pyruvate produced by glycolysis converted into acetyl Co-enzyme A.
This conversion is actually composed of three steps
Last updated by Andrew Robinson 26th May 2004