The movement of materials through a cell membrane using energy.

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

Answer: (A)

Energy-driven transport across the membrane is active transport. It moves substances against their concentration or electrochemical gradient, which requires energy—usually in the form of ATP powering pumps. A classic example is the sodium-potassium pump, which uses ATP to export Na+ and import K+, creating essential gradients for nerve signaling and nutrient uptake. There are other energy-requiring forms as well, like secondary active transport that uses the energy from an established gradient, and bulk transport such as endocytosis or exocytosis that consumes energy to move large particles. By contrast, diffusion and facilitated diffusion move substances down their gradients without cellular energy, with facilitated diffusion relying on a transport protein but still not requiring energy input.