Which of the following statements is correct about diffusion?

A) It may require a transport protein.

B) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

C) It requires an expenditure of energy by the cell.

D) It involves movement of molecules down a concentration gradient and may require a transport protein.

E) It is an active process in which molecules move from a region of lower concentration to one of higher concentration.

The correct answer is option B) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

Explanation:

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Diffusion is a passive transport process. It does not require transport proteins.

This transport happens from a region of greater concentration, to that of less concentration.

This is called concentration gradient.

After the analysis we conclude, that the correct answer is option B) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.

The right answer is B.

Diffusion is a passive transport (without energy, nor transport proteins) spreading a substance, a wave, in all directions by following the concentration gradient (from most concentrated to at least concentrated).

A number of small molecules O2, CO2, fatty acids, ethanol, can freely cross the cytoplasmic membrane when their concentration in the extracellular medium is greater than that of the intracellular medium.