simple lipid definition Neutral fats Triglycerides (TGs) physical properties chemical properties lipase Rancidity oxidation hydrogenation additive reaction

1. SIMS 305- Clinical Biochemistry
Dr. Ali Raza
Centre for Human Genetics and Molecular Medicine (CHGMM),
Sindh Institute of Medical Sciences (SIMS), SIUT.
Lipids

2. SIMPLE LIPIDS
NEUTRAL FATS
(TRIGLYCERIDES OR TRIACYLGLYCEROL)

3. NEUTRAL FATS
E.g. Triglycerides (trihydric glycerol, TG)
• ALL are triesters of trihydric alcohol, glycerol with various
fatty acids
R= fatty acid (same or different)

4. Physical Properties of Neutral Fats
Colourless, odour less, tasteless
Soluble in organic fat solvent/ insoluble in water
Specific gravity is less than 1, float in water
Emulsion of fat may be made by shaking vigorously
in water
Emulsifying agents ( gums, soap)

5. NEUTRAL FATS
Fat is emulsified in intestinal canal by bile salts,
prerequisite for digestion and absorption of fats
The hardness or consistency of fats is related to
their Melting point
Glycerides of lower FA and Unsaturated FA
Glycerides melt at low temperature.

6. Chemical Properties of Neutral Fats
1-Hydrolysis
Fats may be hydrolyzed with:
• Super heated steam, By acids, or alkalies, or
• By the specific fat splitting enzymes lipases

7. Lipase
Found in
•Saliva
•Gastric juice
•Pancreatic juice
•Intestinal epithelial cells
• Adipose tissues
•Serum

8. Lipase
Hydrolyze a triglyceride  FA + glycerol
Pancreatic lipase hydrolyses esters at C1 and C3

9. 2-Saponification
Hydrolysis of fats by alkali
Yield glycerol and alkali salt of FA (soap)
Soaps are cleaning agent because of
emulsification action
High MW and unsaturated degree are Germicides
 Example: Na-ricinoleate” for diphtheria and
tetanus toxin

10. 2-Additive Reaction
•Unsaturated FA present in neutral fats exhibits
additive reaction such as Hydrogenation,
halogenations
Hydrogenation
Liquid  solid state
(oil to fats)
e.g. Vanaspati ghee.

11. 3-Oxidation
Unsaturated FA undergo oxidation at double( =)
bond and forms aldehydes or ketones
Form a transparent coating on the surface to
which oil is applied
Called Drying oil
Used in paints and varnishes

12. 4-Rancidity
 On aging, unpleasant odour and taste develop by most
natural fats
Hydrolysis of fats:
yields FA + glycerol + glycerides
•Reaction is speed up by
•High temperature and
•Moisture

13. 4-Rancidity
Oxidation process:
 Oxidation of double bonds (=) of unsaturated Glycerides
forms “ Peroxidases”
 Then decompose to form aldehyde of objectionable
odour and taste.
Light accelerates such reaction.

14. 4-Rancidity
 Vegetable fats preserve longer than animal fats.
Prevention: antioxidant prevent oxidation
Examples :
Vitamin E
 Hydroquinone

15. 15
Reference:
Textbook Medical Biochemistry by
Chatterjea,
Sixth Edition, Chapter 4
https://www.amazon.com/Textbook-Medical-
Biochemistry-M-D-Chatterjea/dp/9350254840