Lipids are organic compounds formed from fatty acids and alcohols. They are insoluble in water but soluble in organic solvents. Lipids serve important functions like energy storage, cell signaling, and transporting fat-soluble vitamins. They are classified into simple lipids like triglycerides and waxes, compound lipids containing additional substances like phospholipids and glycolipids, and derived lipids formed by hydrolysis of other lipids. Some clinical implications of lipids include obesity, atherosclerosis, and phynoderma.

1. BIOCHEMISTRY OF LIPIDS
GATLUAK JAMES KEDOK JIEK JANY (BBLT, MUK)

2. Learning Objectives
A) Definition
B) Characteristics
C) Clinical Significance
D) Classification
E) Important Questions

3. A) Definition
Lipids are organic compounds formed mainly from alcohol and fatty acid combined
together by ester linkage.

4. B) Characteristics
i) Lipids are insoluble in water but soluble in organic solvents (benzene, acetone,
etc).
ii) They are widely distributed in nature – both in plants and animals.
Biological Significance
i) Lipids are basically the storage of warm energy.
ii) They act as metabolic regulators.
iii) Act as emulsifying agents (surfactant).
iv) Act as electrical insulators in neuroma.
v) Supply fat soluble vitamin in the body (A,D,E,K).
vi) Supply essential fatty acids.

5. C) Clinical Significance
i) Obesity
ii) Atherosclerosis
iii) Phynoderma
D) Classification
Lipids are classified into 3 major groups
1) Simple Lipid: Ester of fatty acid with various alcohols.
a) Triglyceride: Ester of fatty acid with glycerol, also called as Tg/Triacylglycerol.
There are 2 types of Tg – Simple and Mixed Tg.
b) Waxes: Ester of fatty acid with cetyl alcohol (Higher molecular weight than
glycerol).

6. 2. Compound/Conjugated/Complex Lpids: These are lipids that contain additional
substance (Phosphoric acid, protein, carbohydrate , etc).
a) Phopholipid: These are in 2 types
They are the compound lipids that contain fatty acid, alcohol and phosphoric acid
(As additional substance). [Fatty Acid + Alcohol + N2 base + P].
i) Glycerophopholipid: FA + Glycerol + Phosphoric Acid (Example; Lesithin,
Sefalin).
ii) Shingophospholipid: FA + Sphingosine + Phosphoric Acid (Example;
Sphingomyelin).
b) Glycolipid: These are the compound lipids containing fatty acid, alcohol and
carbohydrate (As additional substance). Example; Cerebrosides, Gangliosides) [FA +
Alcohol + Carbohydrate].

7. c) Lipoproteins: They are the compound lipids containing fatty acid, alcohol and
proteins (As additional Substance). [FA + Alcohol + Protein]. Example; HDL, LDL,
IDL, VLDL, Chylomicron.
d) Others: Sulpholipid, Aminolipid, etc.
3. Derived Lipids: They are derived from simple and compound lipid by hydrolysis.
Example; Cholesterol, Steroid hormones, MAG, DAG, Fatty Acid, Fatty Alcohol, etc.

8. E) Important Questions
1) Write short notes on Lipoproteins.
2) Give examples of Glycerophospholipid.
3) Write short notes on Phopholipids.
4) Classify Lipids.
5) Write short notes on Neutral Fats.