Factors Influencing Facilitated Diffusion Rate

Steps:

• Identify facilitated diffusion as passive transport via carrier or channel proteins, limited by saturation.
• Note rate depends on concentration gradient driving net movement.
• Recognize more transport proteins increase overall transport capacity.
• Confirm temperature affects protein kinetics and diffusion speed.

Why A is correct:

• All three factors—concentration gradient, number of transport proteins, and temperature—directly impact rate per Fick's law extension for facilitated processes, where flux = permeability × concentration difference.

Why the others are wrong:

• B excludes 3, but temperature alters molecular collisions and enzyme-like protein activity.
• C excludes 1, but gradient provides driving force for diffusion.
• D includes only 3, ignoring gradient and protein quantity as key regulators.

Final answer: A