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The product of this reaction, acetyl-CoA, is the starting point for the citric acid cycle. [[Acetyl-CoA carboxylase|Acetyl-CoA]] may also be obtained from the oxidation of [[fatty acid]]s. Below is a schematic outline of the cycle:
* The [[citric acid]] cycle begins with the transfer of a two-carbon [[acetyl]] group from acetyl-CoA to the four-carbon acceptor compound (oxaloacetate) to form a six-carbon compound (citrate).
* The citrate then goes through a series of chemical transformations, losing two [[carboxyl]] groups as [[Carbon dioxide|CO2]]. The carbons lost as CO2 originate from what was oxaloacetate, not directly from acetyl-CoA. The carbons donated by acetyl-CoA become part of the oxaloacetate carbon backbone after the first turn of the citric acid cycle. Loss of the acetyl-CoA-donated carbons as CO2 requires several turns of the citric acid cycle. However, because of the role of the citric acid cycle in [[anabolic|anabolism]], they might not be lost, since many citric acid cycle intermediates are also used as precursors for the [[biosynthesis]] of other molecules.
* Most of the electrons made available by the oxidative steps of the cycle are transferred to NAD+, forming NADH. For each acetyl group that enters the citric acid cycle, three molecules of NADH are produced. The citric acid cycle includes a series of oxidation reduction reaction in mitochondria.
* In addition, electrons from the succinate oxidation step are transferred first to the [[FAD]] cofactor of succinate dehydrogenase, reducing it to FADH2, and eventually to [[ubiquinone]] (Q) in the [[Mitochondrion|mitochondrial membrane]], reducing it to [[ubiquinol]] (QH2) which is a substrate of the [[Electron transport chain|electron transfer chain]] at the level of [[Complex III]].
* For every NADH and FADH2 that are produced in the citric acid cycle, 2.5 and 1.5 ATP molecules are generated in oxidative [[phosphorylation]], respectively.
* At the end of each cycle, the four-carbon [[Oxaloacetic acid|oxaloacetate]] has been regenerated, and the cycle continues.

Translations:Citric acid cycle/9/en - Revision history

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