Question

Which of the following statements about diffusion of substance X across a plasma membrane is true?

a. The smaller the molecular weight of X is, the slower its diffusion.
b. The more soluble X is in nonpolar solvents, the easier it is for X to diffuse across the membrane.
c. If X is water, its rate of diffusion across membranes is high.
d. If X is water soluble, its diffusion across membranes will be fast even when its molecular weight is large.

Answer 1

If X is water-soluble, its diffusion across membranes will be fast even when its molecular weight is large.

Step-by-step explanation:

The correct statement about the diffusion of substance X across a plasma membrane is option d. If X is water soluble, its diffusion across membranes will be fast even when its molecular weight is large. Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration, and it occurs down the concentration gradient without requiring energy. While larger molecules move more slowly, the solubility of X in water enables its fast diffusion across membranes.