Lipids Qualitative

Lipids are the body’s principal energy reserve. About 85% of the deaths caused by cardiovascular disease are due to arteriosclerosis Lipids play vital roles both functionally and structurally in our bodily processes. – Insulate

Classification of lipids Simple lipids, compound lipids, steroids, terpenes,

Classification of Clinically Important lipids

Simple lipids Include; – Fats, oils, and waxes

The general structural formula for fats and oils

Saturated – Rich energy reserves Unsaturated – Unsaturated fatty acids twist and bend Inhibits close packing Membrane fluidity

Compound Lipids Include – Phospholipids, sphingolipids, & glycolipids.

A typical phospholipid

Phospholipids can be classified according to the alcohol esterified to the phosphate group. – Lecithins – Cephalins Components of cell membranes

Steroids Common structure – A 17-carbon 4-fused ring system The modifications include – Ring substituents Hydrocarbon chains, hydroxyl groups, carbonyl groups & Other modifications include double bonds

The steroid ring system

Cholesterol

– the most abundant steroid in the body – a major component of cellular membran – an important precursor – Associated with atherosclerosis

In order for lipids to be transported by the blood they must be complexed with water- soluble proteins known as lipoproteins

Generalized structure of a plasma lipoprotein

Identifying Lipids by Their Physical Properties – Solubility Test Hydrocarbon content The relative amounts of charged groups The ionic character – Altered by changes in solvent pH – Emulsification Test

chemical reactions to determine the presence of general structural features of lipid molecules

Saponification Test for Triglycerides

Halogenation Test for Unsaturated Lipids – Addition reaction Hydrogenation – Oils, changed to fats Liebermann–Burchard Test for Cholesterol – The Liebermann– Burchard reagent, a mixture of acetic anhydride & sulfuric acid Ammonium Molybdate Test for Phosphate

The yellow ammonium molybdophosphate precipitates from the reaction mixture

the physical properties that are characteristic of lipids as a general class of compounds Chemical reactions – Determine specific structural information about individual lipids