Sterols are divided into which three categories?

There are three types of sterols. Sterols are derivatives of cyclopentane polyhydrophenanthrene, also known as steroids, which are lipids, mainly cholesterol, steroid hormones and bile acids.

Sterol (English: sterol), also known as sterol, is a class of steroids, containing hydroxyl steroids. They are all based on cyclopentane polyhydrophenanthrene as the basic structure, and contain hydroxyl groups, so called sterols. Using alkaline solution to extract lipids in animal and plant tissues, there are often many different substances that cannot be saponified by alkali.

There are many kinds of sterols, which are widely distributed in the biological world. For example, cholesterol is an important component of higher animal cells. Cholesterol esters formed with long-chain fatty acids are important components of plasma lipoproteins and cell membranes. Plant cell membranes contain other sterols such as stigmasterol and sitosterol. Fungi and yeasts contain sterols.

A class of cyclopentane polyhydrophenanthrene derivatives formed by the condensation of three hexane rings and one cyclopentane. In addition to the lack of bacteria, widely present in the cells and tissues of animals and plants. Sterols have a variety of different biological functions, such as being a component of cell membranes and constituting adrenal cortical hormones and sex hormones.

Many plant sterols also have strong pharmacological or toxicological effects, such as digitalis and ouabain can enhance myocardial contraction, is a good medicine for the treatment of heart failure. Plants contain beta-sitosterol and yeast contain ergosterol. Steroids in animals are rich in cholesterol, which can be converted into sterol hormones-progesterone, estradiol, testosterone, cortisol and aldosterone in the body.

Many contraceptives are progesterone derivatives; some testosterone analogs are promoters of protein biosynthesis in the body. 7-Dehydrocholesterol in the skin by ultraviolet radiation can be converted into vitamin D3 (cholecalciferol), the latter in the body can be converted to regulate calcium and phosphorus metabolism of hormone -1,25-dihydroxycholecalciferol.

Ecdysone, which causes insect molting, and brown toxin against staphylococci are also sterols. The frog toxin secreted by the Columbian poison arrow frog (Phyllobates aurotaenia) can block the transmission of nerve impulses between neuromuscular muscles in trace amounts. The final metabolic product of cholesterol in the body is bile acids, while other sterols are biotransformed to increase their polarity and excreted from the body.