MCAT Organic Chemistry

Background

Steroids

Steroids are a type of lipid organic compound containing 4 cycloalkane rings joined together. They help perform many functions within the human body and are created by a unique biosynthetic mechanism. Steroids are formed from the cyclization of squalene, a type of terpene.

Steroids are commonly used as hormones in the human body, with the best examples of them being cholesterol and the sex hormones testosterone and estrogen.

Terpenes

Isoprene (C₅H₈)

Terpines are formed by the polymerization of units of isoprene. They contain double bonds, which allow for cyclization. The turpentine squalene is the precursor for steroid formation. Squalene contains six isoprene units. Terpines are classified according to the number of isoprene units.

Monoterpines contains 2 isoprene units
Diterpines contains 4 isoprene units
Triterpines contains 6 isoprene units.

Squalene would be an example of a triterpine.

Squalene

Triacyl Glycerols

When a glycerol and three molecules of fatty acids are reacted, they combine to form a triacylglycerol. The reverse of this synthesis is called saponification.

Free Fatty Acids

See Free Fatty Acids