sentences:  The phosphatidylserine decarboxylation pathway and the cytidine diphosphate-ethanolamine pathways are used to synthesize phosphatidylethanolamine.Phosphatidylserine decarboxylase is the enzyme that is used to decarboxylate phosphatidylserine in the first pathway.The phosphatidylserine decarboxylation pathway is the main source of synthesis for phosphatidylethanolamine in the membranes of the mitochondria.