NEET BIOLOGY

Detailed explanation-1: -The simplest mechanism by which molecules can cross the plasma membrane is passive diffusion. During passive diffusion, a molecule simply dissolves in the phospholipid bilayer, diffuses across it, and then dissolves in the aqueous solution at the other side of the membrane.

Detailed explanation-2: -In simple diffusion, the substance passes between the phospholipids; in facilitated diffusion there are a specialized membrane channels. Charged or polar molecules that cannot fit between the phospholipids generally enter and leave cells through facilitated diffusion.

Detailed explanation-3: -Facilitated diffusion is the process of moving molecules from high to low concentration across a membrane by using a protein channel in the membrane. Facilitated diffusion does not use energy but relies on a protein to facilitate movement.

Detailed explanation-4: -In facilitated transport, membrane proteins assist the diffusion of materials through the cell membrane. The protein binds the molecule being transported on the surface of the membrane, then passes it to interior proteins that typically form a channel or pore in the membrane.

Detailed explanation-5: -A transport protein completely spans the membrane, and allows certain molecules or ions to diffuse across the membrane. Channel proteins, gated channel proteins, and carrier proteins are three types of transport proteins that are involved in facilitated diffusion.