Cholesterol is a type of lipid that can be made by the body or come from your diet. Cholesterol has a number of roles in your body and is found in cell membranes. Altering the levels of cholesterol affects how easily different substances move in your cell membrane, and too much or too little cholesterol can disrupt the function of your cells.
Cholesterol Sources and Function
Cholesterol is a waxy substance that is important for the function of your body. Approximately 75 percent of the cholesterol in your body is made by your liver and other tissues. The remaining cholesterol comes from animal-based foods, such as meat, fish, eggs and dairy products. Your body uses cholesterol to make steroid hormones, and cholesterol can also be found in the membranes that surround all of the cells in your body.
Membrane Fluidity
The cell membrane consists of two layers of a kind of fat known as a phospholipid, as well as proteins and other lipids. One of the most important parts of a cell membrane is that it is fluid, which means that different compounds within the cell membrane can move around to other parts of the membrane. This allows the cell membrane to move different proteins around and also lets the membrane respond to changes in temperature and other environmental conditions.
Cholesterol's Role in the Membrane
One of the most important roles of cholesterol in the cell membrane is to maintain membrane fluidity. Cholesterol functions as a spacer in the cell membrane, keeping the different phospholipids from getting too close together. If the phospholipids get too close together, they can clump and make the membrane less fluid. Approximately 20 percent of the cell membrane's mass is made up of cholesterol. Cholesterol can also be enriched in certain parts of the cell membrane, making small sections known as "lipid rafts" that help move proteins around.
Elevated Cholesterol and Cell Membranes
Although cholesterol is an important component for maintaining the fluidity of cell membranes, too much cholesterol in the cell membrane can decrease the fluidity of the membrane. In a 1978 article published in the "Journal of Supramolecular Structure," scientists artificially increased the amount of cholesterol in the membrane that surrounds red blood cells and found that too much cholesterol made the membrane less fluid. This also affected the structure of the cells, impairing their ability to function properly.
References
- American Heart Association: About Cholesterol
- University of California-Davis: Cellular Membranes
- Cholesterol-And-Health.com; Cholesterol's Importance to the Cell Membrane; Chris Masterjohn; 2005
- "Journal of Supramolecular Structure"; Influence of Increased Membrane Cholesterol on Membrane Fluidity and Cell Function in Human Red Blood Cells; Richard A. Cooper; 1978
