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The cytosolic acetyl-CoA can also condense with acetoacetyl-CoA to form 3-hydroxy-3-methylglutaryl-CoA which is the rate-limiting step controlling the synthesis of cholesterol. [16] Cholesterol can be used as is, as a structural component of cellular membranes, or it can be used to synthesize steroid hormones , bile salts , and vitamin D .
In IUPAC nomenclature, an acetyl group is called an ethanoyl group. An acetyl group contains a methyl group (−CH 3) that is single-bonded to a carbonyl (C=O), making it an acyl group. The carbonyl center of an acyl radical has one non-bonded electron with which it forms a chemical bond to the remainder (denoted with the letter R) of the molecule.
Its acetyl-coenzyme A form is the primary input in the citric acid cycle and is obtained from glycolysis, amino acid metabolism, and fatty acid beta oxidation. This process is the body's primary catabolic pathway and is essential in breaking down the building blocks of the cell such as carbohydrates , amino acids , and lipids .
Acyl-CoAs are acyl derivatives formed via fatty acid metabolism. Acetyl-CoA, the most common derivative, serves as an acyl donor in many biosynthetic transformations. Such acyl compounds are thioesters. Names of acyl groups of amino acids are formed by replacing the -ine suffix with -yl.
Co-A then rotates in the active site into the position where acetate can covalently bind to CoA. The covalent bond is formed between the sulfur atom in Co-A and the central carbon atom of acetate. [5] The ACS1 form of acetyl-CoA synthetase is encoded by the gene facA, which is activated by acetate and deactivated by glucose. [6]
The succinyl-CoA formed then enters the citric acid cycle. However, whereas acetyl-CoA enters the citric acid cycle by condensing with an existing molecule of oxaloacetate, succinyl-CoA enters the cycle as a principal in its own right. Thus, the succinate just adds to the population of circulating molecules in the cycle and undergoes no net ...
This four step process repeats until acyl-CoA has removed all carbons from the chain, leaving only Acetyl-CoA. During one cycle of beta oxidation, Acyl-CoA creates one molecule of Acetyl-CoA, FADH2, and NADH. [7] Acetyl-CoA is then used in the citric acid cycle while FADH2 and NADH are sent to the electron transport chain. [8]
This is closely related to the paths of acetyl-CoA: [17] When the body has ample carbohydrates available as energy source, glucose is completely oxidized to CO 2; acetyl-CoA is formed as an intermediate in this process, first entering the citric acid cycle followed by complete conversion of its chemical energy to ATP in oxidative phosphorylation.