Fatty acid synthesis energy costs

Calculating energy costs for the synthesis of a CK, fatty acid from acetyl-CoA is not as simple as you might first think. The major complication is that acetyl-CoA is made in the mitochondria, but fatty acid synthesis occurs in the cytosol—acetyl-CoA can t cross the mitochondrial membrane. Acetyl-CoA gets out of the mitochondria disguised as citrate. The acetyl-CoA is condensed with oxaloacetate to give citrate, and the citrate leaves the mitochondria. In the cytosol, the citrate is cleaved by an ATP-dependent citrate lyase into acetyl-CoA and oxaloacetate ... 

The observed changes in fatty acid composition could be the result of a complete breakdown and resynthesis of cortical phosphohpids or a turnover of only the fatty acids in the sn-2 position, which has the higher proportion of polyunsaturated acyl groups. Turnover of fatty acids in the sn-2 position is well known and is commonly referred to as deacylation-reacylation (Fisher and Rowe, 1980, Anderson and Connor, 1988). This process could have an important role in maintaining optimal membrane composition without the high-energy cost associated with de novo phospholipid synthesis. 

Calculate the energy cost of the synthesis of a given fatty acid. 

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