Diffusion is best described as?

Diffusion is best described as?

• A. Active transport of molecules
• B. Passive process where molecules move from high to low concentration
• C. Movement of air in and out of lungs
• D. Blood circulation through arteries

Answer: (B)

Diffusion is a passive process in which molecules spread from an area of higher concentration to an area of lower concentration due to their random thermal motion. No energy input is required, and the net movement proceeds down the concentration gradient until equilibrium is reached. This down-gradient, energy-free movement applies to gases, liquids, and across membranes, with the rate influenced by the concentration difference, temperature, surface area, and the diffusivity of the substance. Therefore, diffusion is best described as a passive process where molecules move from high to low concentration. The other scenarios involve energy-dependent transport or bulk flows that are not diffusion: active transport uses energy to move substances against a gradient, and ventilation or blood circulation are bulk movements driven by pressure or flow rather than molecular diffusion.

Diffusion is a passive process in which molecules spread from an area of higher concentration to an area of lower concentration due to their random thermal motion. No energy input is required, and the net movement proceeds down the concentration gradient until equilibrium is reached. This down-gradient, energy-free movement applies to gases, liquids, and across membranes, with the rate influenced by the concentration difference, temperature, surface area, and the diffusivity of the substance. Therefore, diffusion is best described as a passive process where molecules move from high to low concentration. The other scenarios involve energy-dependent transport or bulk flows that are not diffusion: active transport uses energy to move substances against a gradient, and ventilation or blood circulation are bulk movements driven by pressure or flow rather than molecular diffusion.