Quiz 13: Lipid Metabolism


The erucic acid ( img ) is a monounsaturated fatty acid having img carbon atoms with as single double bond at 13 th position, so it also notated as 13-docosenoic Erucic 22:1. The fatty acid synthesis occurs by addition of malonyl CoA in the acetyl CoA molecule along with the removal of carbon dioxide on each addition of malonyl CoA (provide 2 carbon atoms). The reaction of a single round is as follows: img Thus, to obtain 22 carbon atoms one acetyl CoA (2 carbon atoms) is reacted with 10 Malonyl CoA ( img carbons atoms). This will provide erucic acid. Hence, the number of condensation steps would be 10 in erucic acid.

The desaturation (removal of hydrogen atoms) of the fatty acid molecule requires oxygen, which takes up two hydrogen atoms, one from each adjacent carbon atoms and form water. This step ultimately forms water, which is interconnected with other steps that ends at producing NAD + (nicotinamide dinucleotide) (oxidized). This oxidized moiety is then used up in the mitochondria for ATP (adenosine triphosphate) formation. Also, the fatty acid desaturation occurs in smooth endoplasmic reticulum (SER). Thus, the desaturation does not affect the ATP formation as after using oxygen, the fatty acids provides reducing equivalents that can be used in the ATP formation.

The ester linked phospholipids can be formed from the GOLP (glycerol phosphate), which is obtained from DHAP (dihydroxyacetone phosphate). On the other hand, if phospholipids are obtained directly from the DHAP then they are formed as ether linked. The ether linked phospholipids have been found to have greater stability than the ester linked. This is because the ether linked- phospholipids can be insoluble in the hydrophilic environment and therefore they are more stable than the ester linked one. The ester bonds are hydrolyzed into carboxylic acid and water, which destabilized the membrane. Also, ether linked phospholipids provide stability to the plasma membrane and salt tolerance.