Which process uses energy to move material through the cell membrane against a concentration gradient?

Which process uses energy to move material through the cell membrane against a concentration gradient?

• A. Passive transport
• B. Diffusion
• C. Osmosis
• D. Active transport

Answer: (D)

Active transport is the process that uses energy to move material through the cell membrane against a concentration gradient. When a substance is more concentrated on one side of the membrane than the other, moving it to the less concentrated side requires energy input, typically in the form of ATP. Transport proteins called pumps power this movement, such as the sodium–potassium pump that moves ions against their gradients. Because energy is spent to push substances uphill, this type of transport is distinct from diffusion and osmosis, which handle movement down the gradient without energy input.

Active transport is the process that uses energy to move material through the cell membrane against a concentration gradient. When a substance is more concentrated on one side of the membrane than the other, moving it to the less concentrated side requires energy input, typically in the form of ATP. Transport proteins called pumps power this movement, such as the sodium–potassium pump that moves ions against their gradients. Because energy is spent to push substances uphill, this type of transport is distinct from diffusion and osmosis, which handle movement down the gradient without energy input.