1. Glycerol: A three-carbon alcohol with three hydroxyl (-OH) groups.

2. Fatty acids: Long chains of hydrocarbons with a carboxyl (-COOH) group at one end.

How they combine:

Glycerol acts as a backbone, and fatty acids attach to each of its hydroxyl groups through ester bonds. This process is called esterification.

Different types of lipids:

The type of lipid formed depends on the number and types of fatty acids attached to glycerol.

* Triglycerides: Most common type, contain three fatty acids.

* Phospholipids: Contain two fatty acids and a phosphate group.

* Steroids: Have a different structure than triglycerides and phospholipids and contain four fused hydrocarbon rings.

Note: While glycerol and fatty acids are the primary building blocks, some lipids, such as steroids, do not contain glycerol.