06/02/2026
Lipids
What are Lipids?
Lipids are a large group of organic biomolecules that are mainly composed of carbon (C), hydrogen (H), and oxygen (O). In some lipids, elements such as phosphorus (P) and nitrogen (N) are also present.
A key feature of lipids is that they are insoluble in water but soluble in organic solvents such as ether, chloroform, or alcohol.
Lipids are commonly known as fats and oils, but biologically, the lipid group is much broader and includes substances like phospholipids, waxes, and steroids.
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General Characteristics of Lipids
•Hydrophobic (do not dissolve in water)
•High energy-yielding molecules
•Stored in the body for long-term energy
•Provide insulation and protection
•Important components of cell membranes
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Classification of Lipids
1. Simple Lipids
These are lipids made from fatty acids and alcohol.
(a) Fats and Oils (Triglycerides)
Made of one glycerol molecule + three fatty acids
Fats are solid at room temperature (e.g., butter, animal fat)
Oils are liquid at room temperature (e.g., coconut oil, sunflower oil)
Fatty Acids Types:
+Saturated fatty acids
•No double bonds
•Solid at room temperature
Example: animal fats
+Unsaturated fatty acids
•One or more double bonds
•Liquid at room temperature
Example: vegetable oils, fish oil
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2. Compound (Complex) Lipids
These lipids contain additional groups besides fatty acids and alcohol.
(a) Phospholipids
•Contain phosphate group
•Major component of cell membranes
•Have a hydrophilic head and hydrophobic tails
Example:>
> lecithin
(b) Glycolipids
•Contain carbohydrate groups
•Important in nerve tissue and brain cells
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3. Derived Lipids
•These are substances derived from simple and •compound lipids.
Examples:>
>Steroids (cholesterol, hormones)
>Fat-soluble vitamins (A, D, E, K)
>Waxes (plant cuticle, ear wax)
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Structure of a Triglyceride (Basic Idea)
1 glycerol molecule
3 fatty acid molecules
Joined by ester bonds
Formed by a condensation reaction (water is released)
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Functions of Lipids
1. Energy Storage
Lipids provide more than twice the energy of carbohydrates per gram
Stored in adipose tissue
2. Structural Role
Phospholipids form the cell membrane
Cholesterol maintains membrane flexibility
3. Insulation and Protection
Thermal insulation under the skin
Protection of vital organs (kidneys, heart)
4. Hormone Production
Steroid hormones like testosterone, estrogen, cortisol are lipids
5. Absorption of Vitamins
Help absorb fat-soluble vitamins (A, D, E, K)
6. Waterproofing
Waxes prevent water loss in plants and animals
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+Sources of Lipids
Animal Sources
Butter
Ghee
Milk
Meat
Egg yolk
Plant Sources
Coconut oil
Olive oil
Sunflower oil
Nuts and seeds
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+Health Aspects of Lipids
∆ Benefits
Essential for normal growth
Support brain development
Maintain healthy skin and hair
∆ Excess Intake Problems
Obesity
Heart diseases
High cholesterol
Atherosclerosis
Balanced lipid intake is essential for good health.
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Difference Between Fats and Oils
Feature Fats Oils
Physical state Solid Liquid
Fatty acids Saturated Unsaturated
Source Animal Plant
