is an activated form of acetic acid, in which the acetate is coupled with Coenzyme A. It is a critically important molecule that takes part in the metabolism of all living organisms. Acetyl CoA can “donate” acetate in a wide range of reactions, including:

(a) the formation of esters and thioesters. Examples of esters produced by brewing yeast are iso-amyl acetate (banana-like flavor, prominent in Bavarian wheat beers) and ethyl acetate (pear-like flavor, commonly found in warm-fermented beers) while a prominent thioester is methyl thioacetate (cooked cabbage flavor)

(b) the synthesis of fatty acids and sterols, which are important membrane constituents of yeast

(c) the synthesis of organic acids: the reaction of acetyl-CoA with oxaloacetate to form citrate is the first step in the tricarboxylic acid cycle, which performs a key function in many living organisms for the provision of energy and building blocks for new cellular material.

See also acetic acid and organic acids.