Lipids - Saponification and Fatty acids

What is the main chemical distinction between saponifiable and nonsaponifiable lipids?

Saponifiable lipids contain ester, amide, or glycosidic bonds that can be hydrolyzed by hot alkali; nonsaponifiable lipids do not contain such hydrolyzable bonds

What is saponification?

Saponification is the hydrolysis of saponifiable lipids in hot alkali to form soaps, which are the sodium or potassium salts of fatty acids

Are saponifiable lipids simple or complex molecules?

They are complex, water-insoluble molecules composed of smaller molecules covalently joined by hydrolyzable bonds

What are nonsaponifiable lipids typically composed of?

Large, hydrophobic molecules that do not react with hot NaOH or KOH because they lack hydrolyzable bonds

What is the general chemical composition of fatty acids?

Fatty acids are carboxylic acids with long hydrocarbon chains. They consist of a polar carboxyl group (-COOH) and a nonpolar hydrocarbon tail.

Why are fatty acids considered slightly amphipathic molecules?

Because they contain a hydrophilic (polar) carboxylic acid group and a hydrophobic (nonpolar) hydrocarbon chain.

What defines saturated fatty acids?

Saturated fatty acids contain only single bonds between carbon atoms, resulting in straight chains that pack tightly and are solid at room temperature.

What defines monounsaturated fatty acids (MUFAs)?

MUFAs have one double bond in the hydrocarbon chain, introducing a kink that reduces tight packing and lowers the melting point.

What defines polyunsaturated fatty acids (PUFAs)?

PUFAs contain two or more double bonds in the hydrocarbon chain, further increasing fluidity and reducing melting point.

What is the ionization state of fatty acids at physiological pH?

They are anions; the carboxylic acid group has donated its proton.

How does solubility change with fatty acid chain length?

Solubility decreases as the number of carbon atoms increases.

How do the melting and boiling points of fatty acids change with increasing carbon atoms?

Both melting and boiling points increase as the carbon chain length increases.

How do double bonds affect the melting and boiling points of fatty acids?

More double bonds lead to lower melting and boiling points.

What effect do “cis” double bonds have on fatty acid structure?

They introduce “kinks” that prevent tight packing into crystalline structures.

What are “bad” trans fatty acids?

They are unsaturated fatty acids with trans double bonds produced industrially during partial hydrogenation of oils.

What is the chemical feature of “bad” trans fatty acids?

They contain trans-configured double bonds that straighten the hydrocarbon chain, making them behave more like saturated fats in membranes.

What are “good” trans fatty acids?

Naturally occurring trans fatty acids like conjugated linoleic acid (CLA) found in dairy and meat

What distinguishes “good” trans fats chemically?

They often have conjugated double bonds (alternating single and double bonds) and are produced by bacteria in ruminant animals, not by industrial hydrogenation.