Question

The principal force driving movement in diffusion is the ________.

1. Temperature
2. Particle size
3. Concentration gradient
4. Membrane surface area

Short answer

Option (c) is the correct answer. The principal force in the diffusion process is controlled by the concentration gradient majorly.

Step-by-step solution

Explanation for correct option (c)

The energy is not required for diffusion but on contrary, the concentration gradient is the type of potential energy which disappears after the gradient is eliminated.

Explanation for incorrect option (a)

Temperature is an incorrect answer because, on the contrary, a concentration gradient is a form of potential energy whereas temperature increases the movement of the molecules by increasing the energy thus diffusion rate increases.

Explanation for incorrect option (b)

Particle size is an incorrect answer because concentration gradient plays an important role in the principal force driving movement in the diffusion whereas cell size does not play any role in the rate of diffusion because large size particles die due to the deficiency of nutrients or due to inability of waste products to leave the cells. So cell must be smaller in size.

Explanation for incorrect option (d).

Membrane surface area is an incorrect answer because an increase in surface area increases the rate of diffusion whereas on the contrary concentration gradient is a type of potential energy.