Which term describes movement of substances across membranes using carrier proteins without energy?

Which term describes movement of substances across membranes using carrier proteins without energy?

• A. Carrier-Mediated Diffusion
• B. Active Transport
• C. Osmosis
• D. Facilitated Diffusion

Answer: (D)

Facilitated diffusion describes moving substances across a membrane with the help of carrier proteins, but without using cellular energy. In this process, a specific carrier protein binds the solute on one side of the membrane, undergoes a conformational change, and releases it on the other side, all while the movement follows the concentration gradient. Because energy isn’t expended, it’s still a form of diffusion, just sped up and specific thanks to the carrier. This is different from active transport, which requires energy to move substances against their gradient, and from osmosis, which is the diffusion of water rather than solutes. The term “facilitated diffusion” is the standard way to describe this energy-free, protein-mediated transport.

Facilitated diffusion describes moving substances across a membrane with the help of carrier proteins, but without using cellular energy. In this process, a specific carrier protein binds the solute on one side of the membrane, undergoes a conformational change, and releases it on the other side, all while the movement follows the concentration gradient. Because energy isn’t expended, it’s still a form of diffusion, just sped up and specific thanks to the carrier. This is different from active transport, which requires energy to move substances against their gradient, and from osmosis, which is the diffusion of water rather than solutes. The term “facilitated diffusion” is the standard way to describe this energy-free, protein-mediated transport.