Which process involves the movement of materials through a cell membrane using energy?

The correct answer is active transport because it specifically refers to the process by which materials are moved across a cell membrane against their concentration gradient, and this movement requires energy in the form of ATP. Unlike passive transport, where substances move from an area of higher concentration to an area of lower concentration without the use of energy, active transport involves the use of cellular energy to transport substances into or out of the cell.

This mechanism is vital for maintaining cellular homeostasis and allowing cells to accumulate essential nutrients or expel waste products, even when these substances are less concentrated outside the cell compared to the inside. Active transport plays a critical role in various cellular functions, including nutrient uptake, ion regulation, and cell signaling.

In contrast, passive transport, diffusion, and osmosis do not require energy. Passive transport encompasses all movement of molecules across the membrane without energy input, while diffusion specifically refers to the movement of particles from an area of high concentration to an area of low concentration, and osmosis specifically deals with the movement of water through a semi-permeable membrane. These processes highlight how molecules can move freely in accordance with their concentration gradients, but they do not involve the energy-dependent mechanisms characteristic of active transport.