Question

Describe the fluid mosaic model for membranes.

Answer 1

Fluid mosaic model was given bu Singer and Nicholsen 1n 1972. According to fluid mosaic model a cell membrane is is made up of a bunch of different molecules that are distributed across the membrane. These all molecules putting together look like a mosaic in microscope. These molecules are constantly moving in two dimensions, in a fluid fashion, similar to icebergs floating in the ocean. The molcules are as follows:

1. Phospholipids: The cell membrane is formed as lipid bilayer in which proteins, carbohydrates and cholesterol molecules are embeded. Lipid bilayer is composed of phospholipid. There are two important parts of a phospholipid: the head and the two tails. The head is a phosphate molecule that is attracted to water (hydrophilic). The two tails are made up of fatty acids (chains of carbon atoms) that aren’t compatible with, or repel, water (hydrophobic). The two tails are composed of saturated and unsaturated fatty acids. The kink present in unsaturated fatty acids plays a role in membrane fluidity, because the kinks increase the space in between the phospholipids, making them harder to freeze at lower temperatures.

2. Proteins: There are two types of proteins present in cell membrane. 1. Integeral proteins: Integral proteins are nestled into the phospholipid bilayer and stick out on either end. 2. Peripheral proteins, which don’t extend across the membrane. They can be attached to the ends of integral proteins, or not, and help with transport or communication.

3. Cholesterol: The cholesterol molecules are randomly distributed across the phospholipid bilayer, helping the bilayer stay fluid in different environmental conditions.