Question

What is the general structure of a triglyceride molecule? Compare and contrast the structure of a triglyceride molecule with that of a phospholipid.

Answer 1

General structure of a triglyceride molecule:

The structure of a triglyceride is composed with the glycerol as main molecule. Glycerol is a triol consists of three hydroxyl groups on three carbons. These hydroxyl groups forms an ester reaction with three fatty acid molecules. The fatty acids can be different types, and the fatty acid structure defines the type of triglyceride. The fatty acids are long chains of carbons generally contains 12 to 24 carbons, with an attached carboxyl group. Each of the three fatty acid molecules undergoes an esterification with one of the hydroxyl groups of the glycerol molecule. The result is a large triester molecule referred to as a triglyceride.

Comparision between triglyceride molecule and phospholipid

The triglyceride molecule and phospholipid have similar structure with slight differences. Although these two lipids have similar structures, they both play different roles in your body.

Both molecules contain glycerol, which makes up a straight portion sometimes called a backbone, and fatty acids. These are long chains made up of hydrocarbons, and they can be either saturated or unsaturated fatty acids depending on the type of chemical bonds they contain. But a triglyceride contains three fatty acids attached to the glycerol backbone, while a phospholipid has two fatty acids plus a phosphate group attached to the glycerol. The phosphate group, a charged molecule made up of phpsohorus and oxygen, not only alters the structure of the lipid, but also its function.

Triglyceride	Phospholipid
Contains glycerol	Contains glycerol
Three fatty acids	Two fatty acids
No phosphate group present	Phosphate group present
Fat	Not fat
Essential nutrient taken by food	Body synthesizes on its own
Make up the cell membrane	Acts as a fat storage
Three water molecules will release during formation of triglyceride	Two water molecules will release during formation of triglyceride

Fats must contain three fatty acids, so triglycerides are the fats but phospholipids are not.

Both play a major role in formation of lipid bilayer. Phospholipids have a more rigid chemical structure compared to triglycerides, so they make cell membranes tougher and help them to hold their shape better than triglycerides alone could do.