MCAT Biology : Types of Lipids

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #271 : Organic Chemistry, Biochemistry, And Metabolism

Which of the following is not a lipid?

Possible Answers:

Galactocerebroside

Glycine

Linolenic acid

Prostaglandin

Correct answer:

Glycine

Explanation:

Lipids are hydrophobic molecules that have low solubility in water and high solubility in nonpolar organic solvents. The following choices all describe lipid molecules, with the exception of glycine. Glycine is an amino acid and contains a carboxyl group (like fatty acid lipids), but also a amine group. These function groups make glycine hydrophilic and polar, unlike lipids.

Example Question #1 : Lipids

Which of the following molecule is a type of terpene?

Possible Answers:

 because it is derived from a pentene

 because it is derived from a pentene

 because it is derived from an isoprene

 because it is derived from an isoprene

Correct answer:

 because it is derived from an isoprene

Explanation:

Terpenes are special classes of lipids that are derived from isoprene units. An isoprene unit’s molecular formula is ; therefore, terpenes must contain a molecular formula that is derived from a empirical formula.

The molecular formula consists of seven isoprene units ( = ); therefore,  is a type of terpene.

Pentene is an alkene with the molecular formula .  () is derived from pentene units; however, terpenes do not have pentene units.

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