Final answer:
The process observed when diffusion is assisted by channel or carrier proteins is called facilitated diffusion, allowing select molecules to pass through the cell membrane without the expenditure of energy (ATP).
Step-by-step explanation:
When a channel protein or carrier protein assists in diffusion, the process observed is facilitated diffusion. This specific type of diffusion involves the use of transport proteins embedded in the cell membrane to help move substances from an area of higher concentration to an area of lower concentration. There are several types of transport proteins that aid in this process, including channel proteins and carrier proteins.
Channel proteins are less selective and primarily discriminate their cargo based on size and charge to facilitate the movement through the membrane. In contrast, carrier proteins are more selective and tend to allow only specific types of molecules to pass.
When a molecule binds to the active site of a carrier protein, the carrier protein changes shape, releasing the molecule on the other side of the membrane before returning to its original shape. This process does not require energy from ATP, distinguishing it from active transport such as ion pumps and endocytosis, which do.