What are Lipids?

Lipids are biomolecules grouped by a shared property. They are hydrophobic, meaning they do not dissolve in water.

This is because they are mainly made of nonpolar hydrocarbon chains that lack charge and cannot form hydrogen bonds with water.

Based on their structure and components, lipids are divided into three classes: fats, phospholipids, and steroids.

Fats, also called triglycerides, are made up of a glycerol molecule and three fatty acids.

They are classified as saturated or unsaturated based on whether their fatty acids have double bonds. Saturated fatty acids have no double bonds in their hydrocarbon chain and carry the maximum number of hydrogen atoms, while unsaturated fatty acids have one or more double bonds.

These saturated and unsaturated fatty acids are also present in phospholipids. However, only two fatty acids are attached to the glycerol, and a charged phosphate group replaces the third fatty acid.

This gives phospholipids a unique feature: a hydrophilic phosphate head and hydrophobic hydrocarbon tails. These molecules form a bilayer that makes up the cell membrane.

The hydrophilic phosphate heads are in contact with the aqueous solution inside and outside the cell, while the hydrophobic tails face each other, away from water.

The third type, steroids such as cholesterol, have a unique fused structure with a carbon skeleton made up of four hydrocarbon rings. Because of this, their chemical structures look very different from those of fats and phospholipids.