The structures of cholesterol and cortisol are shown. Each of these molecules is composed of three six-carbon rings fused to a five-carbon ring. Cholesterol has a branched hydrocarbon attached to the five-carbon ring, and a hydroxyl group attached to the terminal six-carbon ring. Cortisol has a two-carbon chain modified with a double-bonded oxygen, a hydroxyl group attached to the five-carbon ring, and an oxygen double-bonded to the terminal six-carbon ring.
Four fused hydrocarbon rings comprise steroids such as cholesterol and cortisol. Source: OpenStax Biology 2e

OpenStax Biology 2e

Steroids have a fused ring structure. Although they do not resemble the other lipids, scientists group them with them because they are also hydrophobic and insoluble in water. All steroids have four linked carbon rings and several of them, like cholesterol, have a short tail. Many steroids also have the –OH functional group, which puts them in the alcohol classification (sterols).

– What is known as steran or cyclopentanoperhydrophenanthrene which is the simplest steroid and the nucleus of all steroids and sterols?

Cholesterol is the most common steroid. The liver synthesizes cholesterol and is the precursor to many steroid hormones such as testosterone and estradiol, which gonads and endocrine glands secrete. It is also the precursor to Vitamin D. Cholesterol is also the precursor of bile salts, which help emulsifying fats and their subsequent absorption by cells. Although lay people often speak negatively about cholesterol, it is necessary for the body’s proper functioning. Sterols (cholesterol in animal cells, phytosterol in plants) are components of the plasma membrane of cells and are found within the phospholipid bilayer.

– What is a sterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells?

Anabolic steroids are steroidal androgens that include natural androgens like testosterone as well as synthetic androgens that are structurally related and have similar effects to testosterone. They are anabolic and increase protein within cells, especially in skeletal muscles, and also have varying degrees of androgenic and virilizing effects, including induction of the development and maintenance of masculine secondary sexual characteristics such as the growth of facial and body hair. Health risks can be produced by long-term use or excessive doses of anabolic steroid. These effects include harmful changes in cholesterol levels, acne, high blood pressure, liver damage, and dangerous changes in the structure of the left ventricle of the heart. These risks are further increased when athletes take steroids alongside other drugs, causing significantly more damage to their bodies. The effect of anabolic steroids on the heart can cause myocardial infarction and strokes. Conditions pertaining to hormonal imbalances such as gynecomastia and testicular size reduction may also be caused by anabolic steroids. In women and children, anabolic steroids can cause irreversible masculinization.


Clark, M., Douglas, M., Choi, J. Biology 2e. Houston, Texas: OpenStax. Access for free at:


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