Question

Assertion: cell membranes show fluidity.
Reason: fluidity is due to the presence of proteins.
A. Both assertion and reason are correct and reason is the correct explanation for assertion
B. Both assertion and reason are correct but reason is not the correct explanation for assertion
C. Assertion is correct but reason is incorrect
D. Both assertion and reason are incorrect

Answer 1

Because the phospholipids that make up the phospholipid bilayer of the cell membrane are continually moving and switching locations, they behave like a fluid. Because there is a variety of protein embedded across the membrane, the proteins in the membrane are mosaic. Membrane fluidity is aided by the mosaic nature of the membrane, its phospholipid chemistry, and the presence of cholesterol. Fatty acids have an effect on membrane fluidity.

Complete answer:
Option A: Membrane proteins are mobile in the lipid fluid environment; however, due to protein crowding in the membrane and aqueous matrix constraints, lateral diffusion of membrane proteins is slower than predicted by theory. Lipids have the ability to produce the most favorable structure for catalytic activity.
Hence this is an incorrect option.
Option B: Membrane proteins are mobile in the lipid fluid environment; nevertheless, lateral diffusion of membrane proteins is slower than predicted by theory, due to both proteins crowding in the membrane and aqueous matrix restrictions. Lipids have the potential to generate the best shape for catalytic activity.
So, option B is not correct.
Option C: The plasma membrane is the outer coating of all cells, but in plant cells it is found below the cell wall. It has a mosaic-like look and is made up of phospholipid bilayer structure with embedded proteins. Membrane lipid molecules provide fluidity and flexibility, whereas membrane protein provides semi-permeability.
So, option C is correct.
Option D: Membrane fluidity is aided by the mosaic nature of the membrane, its phospholipid chemistry, and the presence of cholesterol.
So, option D is not correct

Therefore, Option C is the correct answer.

Note:
According to the fluid mosaic model, the plasma membrane is composed of a mosaic of components, including phospholipids, cholesterol, proteins, and carbohydrates, which give it a fluid characteristic. Myelin, for example, is $18\%$ protein and $76\%$ lipid. The cell membrane is sometimes referred to as a fluid mosaic because it contains a variety of molecules that float along the lipids due to the diversity of molecules that make up the cell membrane. The lipid bilayer, which floats along the lipids due to the many different types of molecules that make up the cell, is the liquid component.