Lipids

From ArticleWorld

Lipids can be classified as water-insoluble organic compounds. They are formed by a condensation reaction that occurs between a fatty acid and an alcohol. These compounds are essential to the cell as they have structural and other functions.

Structure

Fatty acids which are a component of lipids have a carboxyl group and contain many carbon atoms. Fatty acids generally have these carbon atoms arranged in long chains which form a hydrocarbon tail. These tails are instrumental in determining many of the properties of lipids. These tails are termed to be hydrophobic or water-hating meaning they are insoluble in water. Fatty acids may also contain double bonds between carbon atoms and this means that they are unsaturated. Saturated fatty acids do not have double bonds. Unsaturated fatty acids cause melting points to be lowered.

The majority of lipids are made from the alcohol glycerol and are therefore called triglycerides. The triglycerides are non-polar and they can float on water. They result from a condensation reaction between a glycerol molecule and fatty acids.

Function

Lipids can act as energy stores. They have a higher energy value as compared to carbohydrates due to the presence of more hydrogen in their structure. Lipids are also stored under the skin as insulation in vertebrates and in animals that hibernate, extra lipids are also stored. Plants also store lipids but mainly in their seeds, fruits and chloroplast.

Phospholipids are another type of lipid that is important in organisms. They are made up of polar heads and two non-polar tails in each molecule. These molecules are the basic structures that make up cell membranes. The polar or water-loving heads orient themselves such that they project outwards in water with the non-polar tails on the inside. This is the concept in micelle formation. Some lipids also function as hormones and in interactions with vitamins.