Lipids: Overview
🔹 Definition:
Lipids are organic molecules that are insoluble in water but soluble in non-polar solvents (like chloroform or ether). They are key components of cell membranes, energy storage, and signaling pathways.
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🧬 Main Functions of Lipids:
1. ✅ Energy storage – Fats store more energy than carbohydrates.
2. 🧱 Structural components – Especially in cell membranes (phospholipids).
3. 📡 Signaling molecules – Like steroid hormones and prostaglandins.
4. 🧴 Insulation & protection – Fat cushions organs and maintains body temperature.
5. 🌊 Waterproofing – Waxes on leaves, skin, feathers.
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🧫 Main Classes / Types of Lipids:
1. Simple Lipids
Fats and oils (triglycerides)
Waxes
🔸 Made of: Fatty acids + alcohol (usually glycerol)
2. Compound Lipids
Phospholipids – Important for cell membranes
Ex: Lecithin, Cephalin
Glycolipids – Lipids + carbohydrate
Lipoproteins – Lipids + protein
Ex: HDL, LDL (in blood cholesterol transport)
3. Derived Lipids
Fatty acids, steroids, fat-soluble vitamins (A, D, E, K), cholesterol
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🧪 Fatty Acids:
🔸 Types:
Saturated – No double bonds (solid at room temp)
Ex: Butter, lard
Unsaturated – One or more double bonds (liquid at room temp)
Monounsaturated – Olive oil
Polyunsaturated – Sunflower oil, omega-3
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🧬 Important Lipids in the Body:
Lipid Type Function
Triglycerides Energy storage
Phospholipids Cell membrane structure
Cholesterol Membrane fluidity, hormone precursor
Steroid hormones Regulate metabolism, immunity, sex functions
Prostaglandins Inflammatory response, pain, fever
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🧫 Clinical Relevance:
High cholesterol → risk of heart disease
Essential fatty acid deficiency → skin problems, growth issues
Statins → drugs that lower cholesterol synthesis in liver
Lipid storage diseases → ex: Tay-Sachs, Gaucher's disease
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