<P> The difference between (straight - chain) fatty acid synthase and branch - chain fatty acid synthase is substrate specificity of the enzyme that catalyzes the reaction of acyl - CoA to acyl - ACP . </P> <P> Omega - alicyclic fatty acids typically contain an omega - terminal propyl or butyryl cyclic group and are some of the major membrane fatty acids found in several species of bacteria . The fatty acid synthetase used to produce omega - alicyclic fatty acids is also used to produce membrane branched - chain fatty acids . In bacteria with membranes composed mainly of omega - alicyclic fatty acids, the supply of cyclic carboxylic acid - CoA esters is much greater than that of branched - chain primers . The synthesis of cyclic primers is not well understood but it has been suggested that mechanism involves the conversion of sugars to shikimic acid which is then converted to cyclohexylcarboxylic acid - CoA esters that serve as primers for omega - alicyclic fatty acid synthesis </P> <P> Tuberculostearic acid (- 10 - Methylstearic acid) is a saturated fatty acid that is known to be produced by Mycobacterium spp. and two species of Streptomyces . It is formed from the precursor oleic acid (a monounsaturated fatty acid). After oleic acid is esterified to a phospholipid, S - adenosyl - methionine donates a methyl group to the double bond of oleic acid . This methylation reaction forms the intermediate 10 - methylene - octadecanoyal . Successive reduction of the residue, with NADPH as a cofactor, results in 10 - methylstearic acid </P>

Why are fatty acids important in the formation of new cells