Question

Give the biochemical composition of plasma membrane. How are lipid molecules arranged in the membrane?

Answer 1

Components

The plasma membranes comprises of the following:

* Carbohydrates

* Lipids

* Proteins

* Cholesterol


Carbohydrates

The branched or unbranched chains of oligosaccharides can be associated with lipids or proteins by the process of glycosylation. The categories are stated below:-

* Glycolipids: When carbohydrates are associated with lipids, the complex is called glycolipid.

* Glycoproteins: When carbohydrates are associated with proteins, the complex is called glycoprotein.

Lipids

The plasma membrane is composed of phospholipid bilayer.

Proteins

Membrane proteins are classified as integral and peripheral proteins:

* Peripheral proteins: Surface proteins that are loosely
associated with the membrane.

* Integral proteins: Proteins that are partially or totally buried in the membrane.

Cholesterol

Cholesterol is inserted at specific positions in the phospholipid bilayer which regulates stability of the cell membrane.

Arrangement of lipid molecules in the membrane

In a phospholipid bilayer,

* The polar heads (containing phosphate groups) are projected towards the outer sides facing the external and the cytosolic environment.

* The hydrophobic tails (hydrocarbon tail) are located towards the inner side, sandwiched between the two polar surfaces.