Cholesterol
Biochemistry · Physiology · Medicine
Say it: kuh-LES-tuh-rol
Cholesterol is a waxy steroid lipid found in animal cell membranes and used to make steroid hormones, vitamin D and the bile salts that digest fat.
Definition
What is cholesterol?
Cholesterol is the most common steroid in animals: a lipid built on four fused carbon rings, with a short hydrocarbon tail and a single hydroxyl (OH) group that makes it a sterol. It is a normal part of animal cell membranes, where its molecules sit among the phospholipids and help keep the membrane at the right fluidity. The liver makes most of the body's cholesterol, and more comes from animal foods such as eggs, meat and cheese.
The body uses cholesterol as raw material for steroid hormones such as cortisol, testosterone and estradiol, for vitamin D, and for the bile salts that help digest fat. Because it does not dissolve in blood, it travels inside lipoproteins, particles made of lipid and protein. Low-density lipoprotein (LDL) delivers cholesterol to tissues, and high-density lipoprotein (HDL) carries it back to the liver for removal.
High levels of LDL cholesterol in the blood contribute to atherosclerosis, the buildup of fatty plaque in artery walls that can lead to heart attack and stroke. For this reason, cholesterol levels are a standard part of routine blood tests.
Word parts
Where does the word “cholesterol” come from?
- chole-
- bileGreek kholē
- ster-
- solid, firmGreek stereos
- -ol
- an alcohol (a molecule with an OH group)chemical suffix, from alcohol
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Terms that go with it
- LipidA lipid is one of a varied group of biological molecules, including fats, oils, phospholipids, waxes and steroids, that do not dissolve in water.
- AtherosclerosisAtherosclerosis is a disease in which fatty plaque builds up inside artery walls, stiffening and narrowing the arteries and reducing blood flow.
- Cell membraneThe cell membrane is the thin, flexible boundary of lipids and proteins that encloses every cell and controls what enters and leaves it.
- LiverThe liver is the largest gland and internal organ, lying in the upper right abdomen, where it makes bile, processes nutrients and clears toxins.
- HormoneA hormone is a chemical messenger released into the blood by a gland or cell that changes the activity of distant target cells with matching receptors.
- CortisolCortisol is a steroid hormone made by the adrenal cortex that helps the body cope with stress, raises blood glucose and dampens inflammation.
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