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

• 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