What is the structural difference between a triglyceride and a phospholipid?

A triglyceride has three fatty acid chains attached to a glycerol backbone, while a phospholipid is a modified triglyceride with only two fatty acid chains and a phosphorus-containing group attached to glycerol. This makes the phospholipid a diglyceride with a polar head and two nonpolar fatty acid tails.

The source explains that a triglyceride is composed of glycerol and three fatty acid chains in a 3:1 ratio, forming an E-shaped molecule. A phospholipid is described as a modified triglyceride: it is a diglyceride with a phosphorus-containing group and two fatty acid chains instead of three. The key structural difference is thus the number of fatty acid chains and the presence of the phosphorus-containing group. In a phospholipid, the phosphorus-containing group forms a polar head, while the two fatty acid chains form a nonpolar tail. This structural difference underlies the phospholipid’s ability to interact with both polar and nonpolar molecules, making it suitable for cell membranes, whereas triglycerides are nonpolar storage fats.