Chapter 8

Lipids

A heterogenous class of naturally occurring organic compounds with common solubility properties, insoluble in water but soluble in aprotic organic solvents, and amphipathic in nature.

Fatty acids

Carboxylic acids with hydrocarbon chains containing 4-36 carbons, categorized as saturated, monounsaturated, or polyunsaturated based on double bond presence.

Glycerolipids

Esters of glycerol with three fatty acids, existing as solid fats or liquid oils, serving as the primary storage form of lipids.

Phosphoacylglycerols

Glycerophospholipids where one alcohol group of glycerol is esterified by phosphoric acid, including common types like PC, PE, PS, PG, and PI.

Ceramide based lipids

Lipids with a backbone of shingosine, where fatty acids are attached via amide linkage, found in ceramides and sphingolipids.

Glycolipids

Lipids with carbohydrates bound to the lipid -OH group, often derived from ceramides, including gangliosides with complex carbohydrate moieties.

Eicosanoid

Cell signaling lipids derived from 20-carbon polyunsaturated fatty acids, such as prostaglandins, thromboxanes, and leukotrienes.

Terpenes

Lipids derived from 5-carbon isoprene units, including steroids with fused ring structures like cholesterol.

Biological membranes

Structures composed of lipids and proteins, with polar head groups in contact with water and nonpolar tails buried within the bilayer, exhibiting fluidity regulated by lipid composition.

Fluid mosaic model

Describes the structure of membranes as a fluid bilayer with proteins, glycolipids, and steroids, where lipids act as a solvent for proteins, allowing lateral and rotational movement.