Final answer:
Passive diffusion through membrane channels involves molecules moving along a concentration gradient via channel and carrier proteins, without using cellular energy.
Step-by-step explanation:
How Passive Diffusion Works Through Membrane Channels
Passive diffusion is a process by which molecules move from an area of higher concentration to an area of lower concentration without the use of cellular energy. When certain molecules cannot permeate directly through the cell membrane due to their polarity or size, they rely on membrane channels and carriers for transport, a mechanism known as facilitated diffusion. Proteins like channel proteins and carrier proteins are integral to this process, allowing substances such as ions, glucose, and amino acids to move down their concentration gradient. Channel proteins create hydrophilic pathways that enable specific molecules or ions to passively shuttle across the membrane. In contrast, carrier proteins bind target molecules on one side of the membrane, undergo a conformational change, and release the molecules on the other side, all without expending cellular energy.