Biological Molecules: Lipids, Steroids, and Carbohydrates

A comprehensive vocabulary review of key biological molecules, including the structure and functions of steroids, artificial and modified lipids, and major storage and structural carbohydrates.

Steroids

Lipids characterized by a carbon skeleton consisting of four fused rings with an attached chain of carbons; they alter cell membrane fluidity, act as signaling molecules, and play roles in growth, development, metabolism, and reproduction.

Cholesterol

An essential steroid found in animal cell membranes that serves as the precursor for synthesizing all other steroids; elevated levels in the blood may contribute to cardiovascular disease.

Testosterone

A vertebrate sex hormone that is synthesized from cholesterol.

Hydrogenated vegetable fats

Unsaturated fats that have been chemically converted to saturated fats, which causes their hydrocarbon chains to fit together more closely.

Olestra

An artificial lipid made by attaching fatty acids to a sucrose molecule via condensation; it cannot be hydrolysed by humans.

Starch

The main storage carbohydrate in plants; a polymer of $\alpha$-glucose subunits composed of two types of polymers: amylose and amylopectin.

Amylose

An unbranched, coiled polymer found in starch composed of $\alpha$-glucose subunits joined by 1,4 glycosidic bonds.

Amylopectin

A branched polymer found in starch composed of $\alpha$-glucose subunits joined by both 1,4 and 1,6 glycosidic bonds.

Cellulose

The main structural component of the plant cell wall; composed of unbranched, straight chains of $\beta$-glucose subunits linked by 1,4 glycosidic bonds with hydrogen bonding between adjacent chains.

Glycogen

The main storage carbohydrate in animals and fungi; a highly branched polymer composed of $\alpha$-glucose subunits joined by 1,4 and 1,6 glycosidic bonds, structurally similar to amylopectin.