Which molecule in animal plasma membranes reduces the permeability of the membrane to most biological molecules?
(a) proteins
(b) phospholipids
(c) glycolipids
(d) nucleic acids
(e) cholesterol

The correct answer is option 'e' : Cholesterol

Explanation:

The ease at which materials can be transported across a membrane depends on the membrane permeability. Membrane permeability is basically the ease at which materials are transported across membrane . As we know that upon increasing the viscosity of any fluid it's resistance to deformation increases or it applies a greater resisting force if we try to change the shape of the membrane thus reducing the permeability of the membrane. the increase in cholesterol increases the viscosity of the membrane thus reducing it's permeability.