Which process uses cellular energy to move nutrients from low concentration to high concentration?

• A. Osmosis
• B. Active Transport
• C. Diffusion
• D. Facilitated diffusion

Answer: (B)

Moving substances against their concentration gradient requires energy, and that is what active transport does. By using cellular energy (usually in the form of ATP), transport proteins act as pumps to push nutrients from a region of low concentration to a region of higher concentration. This is essential for tasks like maintaining ion balances or absorbing nutrients when they’re scarce outside the cell.

In contrast, osmosis involves the movement of water across a membrane and does not require energy; water moves from areas of higher water potential (lower solute concentration) to lower water potential (higher solute concentration). Diffusion is the general spread of particles from high to low concentration without energy input. Facilitated diffusion helps molecules cross the membrane via protein channels but still follows the concentration gradient and uses no energy.