Lipids

CHAPTER 15

LIPIDS

REACTION OF FATS AND OILS A) Addition reaction i) Addition of I 2

-high number of Iodin – high degree of unsaturation (double bond) typical procedure: - fat is mixed with wij’s solution (1,1,1-trichloroethane), then left in the dark room. -potasium iodide and deionized water is added - the mixture then titrated with sodium thiosulfate. ii) Addition of H2 - H is added to double bonds of fats and oils – saturated glycerides

B) Oxidation Reactions i) Rancidification – fats and oils are exposed to air to produce carboxylic acids – make the oils unusable. - C=C is oxidized to carboxylic acid - to avoid rancidification, antioxidant is added (flavonoids, tocopherols,ascorbic acid, BHA, BHT) ii) Drying oils - unsaturated oil is exposed to air – hardens to a tough through chemical polymerization - oxygen attacks at the allylic position to form an extremely large cross-linked polymer. -key component of oil paint and varnishes.

c) Saponification - alkaline hydrolysis of esters to form glycerol and salts of the constituents fatty acids - Soap production

SOAPS AND DETERGENTS Sructure of soaps ( Sodium strearate, Na+ C17H35CO2 -)

•

The carboxylate – hydrophilic( water loving) and hydrocarbon tail is hydrophobic (water fearing) • h/c tend to cluster to minimize their contact with water, carboxylate group remain to contact with water = micelles • when water containing dissolved soap is mixed with oil, the hydrocarbon tail will ‘dissolve’ the oil in the center of micelle– broken up into small droplets and washed away in the polar wash water.

Detergent • Posses a long, nonpolar, hydrophobic hydrocarbon chain that is soluble in fats, oils and greases • Posses a polar, hydrophilic end that is soluble in water • Anionic detergents: (-ve)ly charge polar end such as sulfonate or sulfate

• Cationic detergent – (+ve)ly charge polar end such as an ammonium group

• Have significant germicidal properties – used in shampoo, mouthwash, soaps disinfectant skin sprays

• Nonionic detergent- water soluble end is polar and form hydrogen bonds with water such as alcohol.

BIOLIPIDS A)

Steroids – fused rings (3 six-membered rings and 1 five-membered ring) i) Cholesterol – the precursor to all endocrine hormons - nonsaponifiable, nonpolar lipid

cholesterol

ii) Steroid hormones

aldosterone

cortisol

estrogen

progesterone

testosterone

iii) Bile acids – a cholesterol derived detergent molecule, that is secreted by the gall-bladder into the intestine to assist in the absorption of dietary lipids

Taurocholic acid

Glycocholic acid

iv) Toxins

batrachotoxin

digitoxin

B) Vitamins

Vitamin E – tocopherol - antioxidant

Vitamin K = aid in blood clotting

Vitamin D3 – facilitates the absorption of Ca & P into the bones

c) Pigments

Phycoerythrin – red pigment

β-carotene Chlorophyll a

homework The uses of cholesterol, steroid hormones, bile acids, toxins, vitamins and pigments.