Cholesterol, C27H45-OH, a polycyclic zoosterol (animal steroid) as can best be visualized by considering functions independently: the basic ring structure, the minor modifications ring structure and the eight-carbon aliphatic chain. When the basic chemical layout is understood, a space-filling model complete visualization. Cholesterol is not only found in food, but is made in the body
The ring part of the cholesterol is the four-ringed cyclopentanophenanthrene structure. It is given a very specific numbering as shown in the diagram.
The Eight-Carbon Chain
The eight-carbon chain attached to carbon 17 in the ring system, and possesses the simple structure
[–H2 (CH3) C- (CH2) 3 CH (CH3) 2]
From left to right in the formula, carbons in this chain are numbered 21, 20, 22, 23, 24, 25, 26 and 27.
The minor modifications is a hydroxyl group of carbon-3 position, a double bond at carbon-5 through carbon-6 position and two methyl groups — A carbon-10 position (the receiving number 19) and one of the carbon-13 position ( it gets the number 18).
The synthesis of many complex natural substances can be explained in simple rules. The isoprene rule can be used to derive the triterpene molecule, squalene. As Woodward and Bloch demonstrated in 1953, squalene, in turn, cyclized in cholesterol synthesis. Isoprene has very simple chemical structure
H2C = C (CH3) -CH = CH2.
Isopentenyl pyrophosphate (IPP)
The isoprene units that constitute the building blocks of such structures is not really from isoprene itself but from isopentenyl pyrophosphate, which possesses structure
H2C = C (CH3) -CH = CH-OP (O) (OH) -OP (O) (OH) 2.
It is this naturally occurring substance that is responsible for the formation of cholesterol. Note the similarity of this substance to that of isoprene. The only difference is that one of hydrogen of isoprene is replaced by pyrophosphate portion of the molecule.
Structure First Proven
Little is known about cholesterol to work with A. Windhaus and H. Wieland, who fully known its chemical structure in 1932.
Role Cholesterol Plays in Human Body
Helmut Schrott, MD, professor of epidemiology at the University of Iowa College of Public Health and director of the UI Lipid Research Clinic, is quoted,
“Cholesterol is required for cell wall and serves for the production of hormones such as estrogen and testosterone…”
[University of Iowa Health Clinics – “Health Reports”]