Question

As per the Fluid Mosaic Model, what enables the lateral movement of proteins?

Answer 1

Fluid Mosaic Model:

1. To explain the structure of plasma membrane in animal cells, Nicolson & Singer proposed a fluid mosaic model.
2. It states that the plasma membrane is a mosaic of components such as phospholipids, proteins, cholesterol, and carbohydrates.
3. The capability to show movement in the membrane is measured as its fluidity.
4. The lateral movement of proteins is caused by the quasi-fluid nature of lipids.
5. Quasi fluid refers to being partly liquid and partly solid.

Factors affecting fluidity:

1. Temperature- higher the temperature higher is the fluidity.
2. Cholesterol content- at higher temperatures, cholesterol reduces membrane fluidity by increasing intermolecular forces.
3. The tail length of fatty acids- longer the length, less is the fluidity (due to increased interaction between such tails)
4. Saturation of fatty acid tails- higher the number of saturated tails, the lower the fluidity (higher interaction among the tails). whereas a high number of unsaturated tails increases fluidity.

Membrane proteins:

1. Integral membrane proteins are embedded directly in the lipid bilayer.
2. Peripheral membrane proteins are they are not embedded into the lipid bilayer but are indirectly associated with the membrane.

Functions of membrane proteins:

1. Helps in joining two cells together. Example- Cadherins.
2. Some of them act as enzymes. Example- oxidoreductase, hydrolase (important in Electron Transport Chain).
3. Helps in the transportation of water. Example-aquaporins.
4. In signal transduction. Example- G-proteins.