Question

The plasma membrane of animal cell is elastic due to the presence of
A. Lipid
B. Carbohydrate
C. Protein
D. Water

Answer 1

Elasticity of the plasma membrane is due to the fluidity of the plasma membrane and is due to the presence of the component that is majorly present in plasma membrane according to fluid mosaic model.

Complete Answer:
- In 1972, the fluid mosaic model of plasma membrane was proposed by Singer and Nicolson. According to this model, the plasma membrane is composed of lipid bilayer in which the protein molecules are embedded.
- The quasi-fluid nature of lipid enables the lateral movement of protein within lipid bilayer.
- The fluidity of the plasma membrane depends on the lipid composition and temperature.
- This fluid nature of the lipid makes the plasma membrane elastic.

The correct option is A i.e. Lipid.

Additional information: Carbohydrates participate in cell recognition and adhesion either between cell to cell or between cell and pathogen and hence acts as a physical barrier.
Protein helps in the movement of water, ions and some solute molecules and thus provide some permeability to the plasma membrane.
- Water that is having the property of polarity helps in creating the arrangement of lipid bilayer and make it semi permeable by arranging hydrophobic tails inside the plasma membrane and hydrophilic head outside the plasma membrane.

Note: Fluid mosaic model is one of the most acceptable models of the plasma membrane. According to this, phospholipid is the major component in the plasma membrane followed by proteins and carbohydrates. The proportion of proteins, lipid and carbohydrate vary from cell to cell. For example: the ratio of lipid and protein in myelin is 80:20 while in the inner mitochondrial membrane it is 20:80.