The Primary Difference Between Active Transport and Facilitated Diffusion Is

Multiple Choice

The primary difference between active transport and facilitated diffusion is that active transport is the only one of the two in which

A) transporter proteins are required.
B) the direction of transport is [S]_high → [S]_low.
C) the direction of transport is [S]_low → [S]_high.
D) the S concentration gradient provides the energy necessary for S transport.
E) the mechanism is not saturable.