Question

three factors that influence the rate of diffusion across a membrane are the surface area of the membrane, the concentration gradient across the membrane, and the diffusion distance or thickness of the membrane. which of the following circumstances would result in the fastest rate of diffusion of a drug across a cell membrane?
a large surface area, a large concentration gradient, and a small diffusion distance
a small surface area, a small concentration gradient, and a large diffusion distance
a large surface area, a small concentration gradient, and a small diffusion distance
a small surface area, a large concentration gradient, and a large diffusion distance

Explanation:

To determine the fastest diffusion rate, we analyze the factors:

• Surface area: Larger surface area allows more space for diffusion, increasing the rate.
• Concentration gradient: A larger gradient means a steeper difference in concentration, driving faster diffusion.
• Diffusion distance: A smaller distance (thinner membrane) means molecules travel less, speeding up diffusion.

Now, evaluate each option:

• First option: Large surface area (good), large concentration gradient (good), small diffusion distance (good) → all factors favor fast diffusion.
• Second option: Small surface area, small gradient, large distance → all factors slow diffusion.
• Third option: Small concentration gradient → slows diffusion.
• Fourth option: Small surface area, large distance → slows diffusion.

So the first option has all factors that maximize diffusion rate.

Answer:

a large surface area, a large concentration gradient, and a small diffusion distance