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The citric acid cycle has been described as the “hub of the metabolic wheel”. Discuss the roles of the citric acid cycle in the oxidation of various fuel molecules and the provision of carbon skeletons for biosynthesis:
Respiration is the process by which energy in the form of ATP is obtained from food. ... This oxidation takes place in the citric acid cycle. The citric acid cycle is the final common pathway for the oxidation of fuel molecules – amino acids, fatty acids and carbohydrates. Most fuel molecules enter the cycle as acetyl coenzyme A. ...
Figure 2: The molecular structure of acetyl coenzyme A
The citric acid cycle is made up of a series of reactions, which take place inside the mitochondria of cells. During the cycle, oxaloacetate, a four-carbon compound condenses with a two-carbon acetyl unit to yield citrate, a six-carbon tricarboxylic acid. ... As a result of these complete oxidation reactions two carbon molecules leave the cycle as carbon dioxide. ... The main function of the citric acid cycle is to therefore harvest high-energy electrons from carbon fuels.
Figure 3: An outline of the citric acid cycle.
The citric acid cycle also has an anabolic role, as it is an important source of biosynthetic precursors. ...
As the amount of molecules derived form the intermediates from the citric acid cycle increase and are used by cells, the energy requirements of the cells will also increase, thus it is important that the citric acid cycle intermediates must be replenished if they are drawn off for biosynthesis.
Approximate Word count = 1151
Approximate Pages = 4.6
(250 words per page double spaced)
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