Lipid Reactions and Phospholipids

Terminology and chemical reactions related to lipid metabolism, saponification, and the structure of phospholipids and sphingomyelins based on the lecture notes.

Hydrolysis (Lipids)

The reaction in which triacylglycerols split into glycerol and three fatty acids, requiring a strong acid such as $HCl$ or $H_2SO_4$, or digestive enzymes called lipases.

Lipases

Digestive enzymes required for the hydrolysis of triacylglycerols into glycerol and fatty acids.

Saponification

The reaction of a fat with a strong base such as $NaOH$ in the presence of heat, splitting triacylglycerols into glycerol and the salts of fatty acids known as soaps.

NaOH (in Saponification)

A strong base used in saponification to produce solid soaps that can be molded into different shapes.

KOH (in Saponification)

A strong base used in saponification to produce softer, liquid soaps.

Hydrogenation (Lipids)

The reaction of an unsaturated fat containing double bonds with hydrogen in the presence of a $Pt$ or $Ni$ catalyst to produce a saturated fat with single bonds.

Esterification (Lipids)

The reaction between three fatty acids and glycerol to form a triacylglycerol and three water molecules.

Phospholipids

A family of lipids similar in structure to triacylglycerols, which include glycerophospholipids and sphingomyelin.

Glycerophospholipids

Lipids containing two fatty acids forming ester bonds with the first and second hydroxyl groups of glycerol, and a phosphate group linked to an amino alcohol.

Sphingomyelin

A type of phospholipid that contains sphingosine instead of glycerol, a fatty acid, a phosphate group, and an amino alcohol.

Amino alcohols

Components of glycerophospholipids, such as choline, serine, and ethanolamine, which are ionized at the physiological $pH$ of $7.4$.

Lecithin and cephalin

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

Polar head (Glycerophospholipid)

The portion of a glycerophospholipid containing the ionized amino alcohol and phosphate, which is strongly attracted to water.

Nonpolar tail (Glycerophospholipid)

The hydrocarbon hydrocarbon tail portion of a glycerophospholipid that is soluble only in nonpolar substances such as lipids.

Phospholipases

Enzymes found in poisonous snake venom that hydrolyze phospholipids in red blood cells.

Myelin sheath

A coating surrounding nerve cells, abundant in sphingomyelins, that insulates and protects nerve cells while increasing the speed of nerve impulses.

Sphingosine

A nitrogen-containing alcohol that replaces glycerol in the structure of sphingomyelins.

Amide bond (Sphingomyelin)

The bond formed between the amine group of sphingosine and a fatty acid in a sphingomyelin molecule.