Lipids are macromolecules that are insoluble in water. They are present in living organisms and also distributed in nature
Examples of lipids include;
- Fats
- Waxes
- Phospholipids
- Sphingolipids
- Steroids
- Vitamins A, D, E and K
Lipids are one of the classes of 4 major macromolecules (organic compounds) of our body.
They are taken from external sources like food and edible oils. Also, they are made in the body from excess carbohydrates.
There are many types of lipids and vary in terms of structure, properties and functions in the body.
They are insoluble in water and hence called hydrophobic.
Types of Lipids:
Lipids are of two types as
- Simple lipids
- Compound lipid.
Simple lipids: These are the ones that are ester of fatty acid and alcohol. They are again of two types as
- Neutral fats (glycerides): They have an ester of fatty acid and glycerol. They tend to accumulate in our bodies and contribute to weight gain. Ex: all edible oils
- Waxes: These are also esters but have fatty acids linked with non-glycerol alcohol. Ex: Bee wax.
The fats are stored in the body and are used in times of starvation.
Compound lipids: These are complex lipids with an ester of fatty acid, alcohol and other substances. They are mostly involved in the formation of membranes of the body cells. They are of different types like
- Phospholipids: Which are par of cell membrane
- Sphingolipids which are part of the nerve cell membrane
- Steroids, especially cholesterol which form the cell membrane.
Fatty acid Structure:
Lipids are made of long-chain fatty acids esters of alcohols. They are written with the formula.
HOOC-(CH)2-CH3 fatty acids
These fatty acids are obtained from different sources like plants, animals (meat) and even minerals.
Fats are used as a part of the diet. At the same time, a few of them, like shark liver oil and Cod liver oil are used as medicine. Others like liquid paraffin are used as a drug to relieve constipation.