Question

Explain three functions served by lipids in plants and animals:

Answer 1

Lipids are macromolecules. They are the Polymers of glycerides. Glycerides are formed by condensation of glycerol and fatty acids. One molecule of glycerol can condense with up to three molecules of fatty acids. If one molecule of fatty acid is present, then it is called as monoglyceride, if two are present, then it is called as diglyceride and if three are present, then it is called as triglyceride.

Three most important functions of lipids inside a cell are -

1. Along with phosphate they form phospholipids which is the most important component of cell membrane in both prokaryotes and eukaryotes. One molecule of phospholipid is composed of 1 phosphate, one glycerol and up to three molecules of fatty acid. Because of phospholipids, the permeability of plasma membrane can easily be controlled.

2. Along with carbohydrates, they form glycolipids and are present on the surface of plasma membrane. These glycolipids are important molecules of cell signalling and Cell to cell recognition reactions. Other lipids like diacylglycerol and inositol triphosphate are important components of lipids signalling pathway.

3. Some of the hormones present in animals and plants are of lipid origin. The sex hormone oestrogen in females and testosterone in males are both steroid and steroids belong to the class of lipids.

In plants, steroids are called as the sterols and phytosterols are dominant.

Another steroid present in animals is cholesterol which is present mainly in the plasma membrane and helps in lipid reordering.

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