Cholesterol
Cholesterol is a soft waxy substance found in animal cells and body fluids. It is a lipid made up of fat or fat-like molecules. It is found especially in animal fats, but not in plant sources of fat.
Cholesterol is a type of lipid that is called a steroid. Steroids have a special chemical structure made of four rings of carbon atoms. The name Cholesterol ending in "ol" means its chemical structure is that of a steroid with an alcohol group.[1][2] All steroid hormones are made by adjusting the basic chemical structure of cholesterol. Other steroids include hormone steroids like cortisol, estrogen, and testosterone.[1][2]
Cholesterol's main function is as a structural component of cell membranes. It is also the starting material for bile acids that are made by the liver to digest fats, and for steroid hormones.
Almost every cell in the human body can make cholesterol. It can be synthesized (constructed from simpler molecules) outside the body as well.
Hypercholesterolemia is a disorder of people with too much cholesterol in the blood.[3] High levels of cholesterol can lead to atherosclerosis, an inflammatory disease of artery walls in which white blood cells invade the vessel wall and become engorged with cholesterol and other lipids. These areas can slowly close off a blood vessel or can suddenly rupture and trigger formation of a blood clot.
Types
[change | change source]Cholesterol is a lipid (fat), which cannot dissolve in water. The bloodstream is water-based and transports only soluble substances, and cholesterol is transported in a soluble structure called a lipoprotein. Lipoproteins may be classified by density.[4] Doctors often measure the amounts of each different type to find out if someone has hypercholesterolemia.
High density lipoprotein (HDL) transports cholesterol from the body to the liver. There it can be recycled or converted to bile acid and excreted, reducing the amount of cholesterol in the body. For this reason HDL is sometimes called "good cholesterol". People with higher levels of HDL are less likely to have atherosclerosis.
Low density lipoprotein (LDL) transports cholesterol from the liver into the body, increasing the amount of cholesterol there. For this reason LDL is sometimes called "bad cholesterol". People with higher levels of LDL are more likely to have atherosclerosis.
Intermediate and Very low density lipoprotein (IDL & VLDL) and Chylomicrons transport triglycerides around the body. Triglycerides also play a role in atherosclerosis.[5]
Biosynthesis
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Cholesterol biosynthetic pathway
Lovastatin
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Architecture of the lovastatin type I PKS system. Outlined domains are used iteratively. ACP- acyl carrier protein, AD-alcohol dehydrogenase, AT-acyltransferase, DH-dehydratase, KS-ketoacyl synthase, KR-ketoreductase, MT-methyltransferase, ER-enoylreductase, C-condensation, TE-thioesterase. (*)-redundant domain/inactive not used in this step.
Biosynthesis of lovastatin
HMG CoA reductase reaction
Biosynthesis using Diels-Alder catalyzed cyclization
Biosynthesis using broadly specific acyltransferase
Synthesis of compounds 1 and 2
Complete lovastatin synthesis
Additional images
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Cholesterol units conversion
Steroidogenesis, using cholesterol as building material
Space-filling model of the Cholesterol molecule
Numbering of the steroid nuclei
Related pages
[change | change source]References
[change | change source]- 1 2 "Types of Hormones | Biology II". courses.lumenlearning.com. Retrieved 2026-03-28.
- 1 2 "37.2: Types of Hormones - Lipid-Derived, Amino Acid-Derived, and Peptide Hormones". Biology LibreTexts. 2018-07-16. Retrieved 2026-03-28.
- ↑ "Hypercholesterolemia". Retrieved 2026-08-25.
- ↑ "Classifying Lipoproteins: Types and Methodologies". New Medical Life Sciences. Retrieved 2026-08-25.
- ↑ "The Role of Triglycerides in Atherosclerosis: Recent Pathophysiologic Insights and Therapeutic Implications". National Library of Medicine. Retrieved 2026-08-25.
