Final answer:
Facilitated diffusion is the passive transport process moving substances down their concentration gradient via specific transmembrane proteins without the need for cellular energy.
Step-by-step explanation:
The type of carrier-mediated transport that transfers a substance across the membrane from a region of high concentration to low concentration is known as facilitated diffusion. This process involves integral membrane proteins which aid in moving substances down their concentration gradients without the use of cellular energy (ATP). Facilitated diffusion is characterized by its utilization of specific channel proteins or carrier proteins in the cell membrane, allowing substances such as glucose or ions like Na+ to pass through more easily than they would by simple passive diffusion.
Unlike active transport, which requires energy to move substances against their gradient, facilitated diffusion is a form of passive transport that relies on the natural movement of particles down their gradient. The rate at which substances are transported is proportional to the number of transporter proteins in the membrane, and it can become saturated if all the transporters are in use. Examples of facilitated diffusion can be observed with glucose transport or ion channels that are selective for certain substances like sodium or potassium ions.