What is the primary structural difference between phosphatidylcholine and phosphatidylethanolamine?

Phosphatidylcholine has a glycerol backbone, while phosphatidylethanolamine does not.

Phosphatidylcholine has choline attached to the phosphate group, while phosphatidylethanolamine has ethanolamine.

Phosphatidylcholine is a sphingolipid, while phosphatidylethanolamine is a glycerophospholipid.

Phosphatidylcholine contains two fatty acids, while phosphatidylethanolamine contains one.