Question

The common feature shared both by simple diffusion and facilitated diffusion is

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

Answer 1

The correct option is D both involve the movement of substances from regions of higher concentration to lower concentration without expenditure of energy.

Simple diffusion and facilitated diffusion are means of short-distance transport of molecules or ions. In simple diffusion and facilitated diffusion, the molecules move from a region of higher concentration to a region of lower concentration (along the concentration gradient) without the expenditure of energy (ATP).

Unlike simple diffusion, facilitated diffusion involves membrane proteins (channel proteins and carrier proteins) to move substances across the membrane. Channel proteins form pores in the membrane through which the substances get transported. The carrier proteins bind to molecules that need to be transported and undergo changes in their structure so as to move the molecules on to the other side of the membrane.