Cell Biology Interview Question:

What are the basic constituents of the cell membrane?

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The cell membrane is formed of lipids, proteins and carbohydrates.

The membrane lipids are phospholipids, a special type of lipid to which one extremity a phosphate group is bound thus assigning electric charge to this region of the molecule. Since phospholipids have one electric charged extremity and a long neutral organic chain they can organize themselves in two layers of associated molecules: the hydrophilic portion (polar) of each layer faces outwards in contact with water (a polar molecule too) of the extracellular and the intracellular space and the hydrophobic chains (non polar) faces inwards isolated from the water. Because this type of membrane is made of two phospolipid layers it is also called bilipid membrane.

Membrane proteins are embedded and dispersed in the compact bilipid structure. Carbohydrates appear in the outer surface of the membrane associated to some of those proteins under the form of glycoproteins or bound to phospholipids forming glycolipidis. The membrane carbohydrates form the glycocalix of the membrane.

This description (with further explanations) is kown as the fluid mosaic model about the structure of the cell membrane.

Cell Membrane Review - Image Diversity: phospholipid bilayer membrane proteins glycocalyx
Submitted by: Administrator