Figure 19.2 schematically depicts the primary pathways of prokaryotic and eukaryotic glycerophospholipid biosynthesis. Note that the center pathway shown in purple occurs in both prokaryotic and eukaryotic cells. Figure 19.3 shows the molecular synthesis of CDP-diacylglycerol starting from glycerol-3-Phosphate.

Phosphatidic Acid, the precursor to CDP-diacylglycerol, usually contains two different acyl groups. The fatty acid on carbon 1 of glycerol (R1 in Figure 19.3) is saturated about 90% of the time. Conversely, the fatty acid on carbon 2 of glycerol (R2 in Figure 19.3) is unsaturated about 90% of the time.

Phosphatidic acid is a branch point between the synthesis of fats and other glycerophospholipids. The high energy anhydride bond between the cytidylic and phosphatidic acid in CDP-diacylglycerol provides an activated intermediate for addition of polar head groups on the phosphate.

One pathway from CDP-diacylglycerol leads to phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC), as shown in Figure 19.2 and Figure 19.4. A different pathway from CDP-diacylglycerol leads to phosphatidylglycerol and cardiolipin.