Question

What characteristic is shared by simple diffusion and facilitated diffusion?

• A. Both require cellular energy for the transport of substances.
• B. Both involve the movement of water across a semipermeable membrane.
• C. Both require a special carrier molecule to move substances across the membrane.
• D. Both involve the movement of a substance from regions of a higher concentration to lower concentration without cellular energy.

Answer 1

The correct option is D

Both involve the movement of a substance from regions of a higher concentration to lower concentration without cellular energy.

Diffusion is the movement of molecules from the higher to a lower concentration. Facilitated diffusion is a type of diffusion in which substances move through the cell membrane, with the help of carrier proteins, along the concentration gradient. These substances are insoluble in lipids, hence need the help of a proteinaceous carrier molecule.