Facilitated diffusion is a passive transport process where specific molecules move across cell membranes through protein channels or carriers, down their concentration gradient, without the expenditure of cellular energy. It is crucial for the transport of polar and large molecules that cannot directly diffuse through the lipid bilayer of the cell membrane.

Facilitated Diffusion

Facilitated diffusion

passive transport process

specific molecules

Cell membranes are selectively permeable barriers that surround cells, maintaining homeostasis by regulating the movement of substances in and out of the cell. They are composed of a phospholipid bilayer with embedded proteins that facilitate communication and transport across the membrane.

cell membranes

protein channels

carriers

A concentration gradient is the gradual change in the concentration of solutes in a solution between two regions, which often drives the movement of substances in biological and chemical processes. This gradient is a fundamental principle in diffusion, where particles move from areas of higher concentration to areas of lower concentration until equilibrium is reached.

concentration gradient

cellular energy

Transport of polar molecules

Transport of large molecules

directly diffuse

The lipid bilayer is a fundamental structural component of cell membranes, providing a semi-permeable barrier that regulates the movement of substances in and out of the cell. Composed primarily of phospholipids, its amphipathic nature allows for the formation of a hydrophobic interior and hydrophilic exterior, crucial for maintaining cellular integrity and facilitating cell signaling.

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