The plasma membrane, which surrounds each cell in your body, fulfills three main functions: it forms a barrier between the cell and its environment; it controls the movement of substances in and out of the cell; and it provides the means for signals to be sent to and from the cell. Cholesterol supports all of these functions.
Membrane Structure
All cell membranes consist of a double layer of phospholipid molecules in a tightly packed formation. In human plasma membranes, proteins and cholesterol are interspersed within this phospholipid bilayer.
Support
The molecules of the membrane are constantly moving relative to each other, which makes the membrane fluid and flexible. Cholesterol is a relatively "stiff" molecule, so its function is to keep membranes from becoming too fluid.
Blockage
Cholesterol molecules keep the membrane from being too permeable. They do this by plugging up "holes" in the phospholipid bilayer, so that certain substances cannot pass.
Communication
Areas within the plasma membrane called "rafts" are made of proteins, cholesterol, and other molecules. These rafts serve as platforms for the transmission of signals, and cholesterol is the "glue" that holds the rafts together.
Misconceptions
Too much cholesterol can cause atherosclerosis (the buildup of plaque in your arteries) and heart disease (coronary artery disease). However, the right amount of cholesterol is crucial to the health of every cell in your body.
