Chapter 15: Lipids

Flashcards covering the definitions, structures, and chemical properties of lipids, including fatty acids, triacylglycerols, and phospholipids from Chapter 15.

Lipids

Biomolecules that contain fatty acids or a steroid nucleus, are soluble in organic solvents but not in water, and are named from the Greek word "lipos" meaning "fat."

Steroid Nucleus

A structure characterized by four fused carbon rings, found in lipids that do not contain fatty acids and cannot be hydrolyzed.

Fatty Acids

Long, unbranched carbon chains with a carboxylic acid group at the end, typically $12-$ to $18-$carbon atoms long.

Saturated Fatty Acids

Fatty acids that contain only $C-C$ single bonds in the carbon chain, allowing them to fit close together in a regular pattern.

Unsaturated Fatty Acids

Fatty acids that contain one or more $C=C$ double bonds in the carbon chain.

Monounsaturated Fatty Acids

Fatty acids containing only one double $C=C$ bond in the carbon chain.

Polyunsaturated Fatty Acids

Fatty acids containing at least two double $C=C$ bonds in the carbon chain.

Lauric acid

A saturated fatty acid with $12$ carbon atoms ($12:0$) commonly found in coconut, with a melting point of $44^ ext{o}C$.

Stearic acid

A saturated fatty acid with $18$ carbon atoms ($18:0$) found in animal fat, with a melting point of $69^ ext{o}C$.

Essential Fatty Acids

Polyunsaturated fatty acids such as linoleic acid, linolenic acid, and arachidonic acid that humans cannot synthesize in sufficient amounts and must obtain from the diet.

Prostaglandins

Hormone-like substances, also called eicosanoids, formed from the $20-$carbon arachidonic acid; they functions in blood pressure regulation and muscle contraction.

NSAIDs

Nonsteroidal anti-inflammatory drugs, such as aspirin and naproxen, that block the production of prostaglandins to decrease pain and inflammation.

Omega-3 Fatty Acids

Unsaturated fats found in fish where the first double bond occurs at carbon $3$ counting from the methyl end of the chain.

Waxes

Esters of saturated fatty acids and long-chain alcohols, each containing from $14$ to $30$ carbon atoms.

Triacylglycerols (Triglycerides)

The major form of energy storage for animals, consisting of esters of glycerol and three fatty acids.

Fats

Triacylglycerols that are usually solid at room temperature and typically come from animal sources like meat and butter.

Oils

Triacylglycerols that are usually liquid at room temperature and obtained from plant sources like olives or corn.

Hydrogenation

A reaction where hydrogen gas is bubbled through heated oil in the presence of a nickel catalyst ($Ni$) to convert $C=C$ double bonds into $C-C$ single bonds.

Trans Fatty Acids

Fatty acids with bulky groups on opposite sides of the $C=C$ bond; they behave like saturated fatty acids in the body and can raise $LDL$-cholesterol.

Saponification

The reaction of a fat with a strong base ($NaOH$ or $KOH$) and heat to produce glycerol and the salts of fatty acids, commonly known as soap.

Glycerophospholipids

Lipids containing two fatty acids forming ester bonds with glycerol, and a phosphate group linked to an amino alcohol.

Sphingomyelin

A phospholipid containing sphingosine instead of glycerol, an amide-linked fatty acid, and a phosphoester bond to choline or ethanolamine; abundant in the myelin sheath.

Amino Alcohols

Components of glycerophospholipids, specifically choline, serine, and ethanolamine, which are ionized at a physiological $pH$ of $7.4$.

Lecithin and Cephalin

Two types of glycerophospholipids that are abundant in brain and nerve tissues, and also found in egg yolk, wheat germ, and yeast.

Myelin Sheath

A coating surrounding nerve cells that increases the speed of nerve impulses and insulates the cells; it is rich in sphingomyelins.