Cell Membrane Structure and Function

Fluid Mosaic Model

The currently accepted model of the cell membrane structure (too small to be seen) characterized by the constant movement (fluid) of its many different molecules (mosaic).

Phospholipid

A molecule made up of lipids with a phosphate group attached, forming the main structure of the cell membrane.

Bilayer

The arrangement of phospholipids in two layers in the cell membrane.

Hydrophilic

Water loving; refers to the polar head of phospholipid molecules that face outward.

Hydrophobic

Water hating; refers to the non-polar tail of phospholipid molecules that face inward.

Cholesterol

Molecules wedged between phospholipid molecules that provide flexibility and structural integrity to the membrane.

Receptor Proteins

Peripheral proteins that enable the cell membrane to communicate with other cells.

Channel Proteins

Integral proteins that transport small, polar molecules such as water across the cell membrane.

Carrier Proteins

Integral proteins responsible for facilitated diffusion and active transport of substances across the cell membrane.

Functions of the Cell Membrane

Acts as a physical barrier, regulates material passage, senses changes, and helps support the cell.