Fluid Mosaic Model of Plasma Membrane

The fluid mosaic model of plasma membrane describes the structure of the cell membrane as a fluid and dynamic layer composed of different molecules. This model was proposed by S.J. Singer and G.L. Nicolson in 1972. The model explains that the cell membrane is composed of two layers of phospholipids, in which proteins are embedded.

Phospholipid Bilayer

The plasma membrane is made up of a phospholipid bilayer, which consists of two layers of phospholipid molecules. The phospholipids are composed of a hydrophilic head and a hydrophobic tail. The hydrophilic head is attracted to water, while the hydrophobic tail is repelled by water. The phospholipids arrange themselves in such a way that the hydrophilic heads face the outside of the membrane, while the hydrophobic tails face inward.

Bimolecular Layer

The phospholipids form a bimolecular layer in the middle part of the membrane. This layer acts as a barrier that separates the inside of the cell from the outside environment. The barrier is selectively permeable, which means that it allows only certain molecules to pass through it.

Proteins

Proteins are embedded in the phospholipid bilayer of the plasma membrane. They are either partially or fully embedded in the membrane. The proteins perform a variety of functions, including transport of molecules across the membrane, signal transduction, and cell recognition.

Fluidity

The fluidity of the plasma membrane allows it to change shape and move. The fluidity is due to the presence of unsaturated fatty acids in the phospholipid bilayer, which prevent the phospholipids from packing tightly together.

Conclusion

In summary, the fluid mosaic model of plasma membrane describes the structure of the cell membrane as a fluid and dynamic layer composed of different molecules. The phospholipid bilayer forms a bimolecular layer in the middle of the membrane, which is selectively permeable. Proteins are embedded in the phospholipid bilayer and perform various functions. The fluidity of the membrane allows it to change shape and move.

In fluid mosaic model, the polar molecules are hydrophilic in nature and located towards the upper side. So, neither option a nor b are correct.
Further, phospholipid bilayer is present in its middle part and the proteins embedded in them are of two types, intrinsic (on inner side) and extrinsic (on outer side). So, most suitable option is c.