AP BIOLOGY

Detailed explanation-1: -Ion channels allows the specific ions that will fit into the channel to flow down their concentration gradient, equalizing the concentrations on either side of the cell membrane. Ion channels and ion transporters accomplish this via facilitated diffusion which is a type of passive transport.

Detailed explanation-2: -Ions pass through channels down their electrochemical gradient, which is a function of ion concentration and membrane potential, “downhill", without the input (or help) of metabolic energy (e.g. ATP, co-transport mechanisms, or active transport mechanisms).

Detailed explanation-3: -Explanation: if transport through ion channel is done down concentration gradient (high to low concentration) then it is facilitated diffusion, and if it is done up concentration gradient (low to high concentration), then it is active transport which requires ATP.

Detailed explanation-4: -Active transport: moving against a gradient To move substances against a concentration or electrochemical gradient, a cell must use energy. Active transport mechanisms do just this, expending energy (often in the form of ATP) to maintain the right concentrations of ions and molecules in living cells.