Lecture Notes: Lipids

Introduction to Lipids

• Large, diverse group of organic compounds.
• Composed mostly of carbon and hydrogen, with little oxygen.
• Insoluble in water (hydrophobic).
• Key terms:
  • Hydrophobic: Water-fearing.
  • Hydrophilic: Water-loving.

Triglycerides

• Known as neutral fats.
• Functions as energy storage, insulation, and building blocks for other lipids.
• Structure:
  • Glycerol backbone.
  • Three fatty acid chains (E-shaped).
• Fatty Acids:
  • Chains of carbons with hydrogens.
  • Vary in length and types of carbon bonds (single or double).
  • Saturated vs. Unsaturated:
    • Saturated: Single bonds, straight chains, solid at room temp (e.g., butter, lard).
    • Unsaturated: Double bonds, kinked chains, liquid at room temp (e.g., olive oil).

Trans Fats

• Found in margarine, baked goods, processed foods.
• Partially hydrogenated plant oils.
• Hydrogenation removes double bonds, making them solid like saturated fats.
• Health effects:
  • Both saturated and trans fats linked to cardiovascular disease.
  • Trans fats are particularly harmful; should be avoided.

Prostaglandins

• Locally acting chemicals derived from fatty acids.
• Three families:
  • Family 1: From plant oils, beneficial.
  • Family 2: From red meats, dairy, trans fats; increase inflammation.
  • Family 3: From cold water fish oils; reduce inflammation.
• Balance is crucial; imbalance can cause diseases like cancer, diabetes, heart disease.
• Trans fats inhibit beneficial prostaglandin production.

Phospholipids

• Constituent of cell membranes.
• Structure:
  • Glycerol backbone.
  • Two fatty acid chains and a phosphate group.
• Amphiphilic nature:
  • Polar head: Hydrophilic.
  • Non-polar tails: Hydrophobic.
• Form a bilayer in cell membranes, creating a barrier between inside and outside.

Steroids

• Flat molecules with four interlocking rings.
• Hydrophobic, soluble in fats.
• Importance of cholesterol:
  • Building block for vitamin D, sex hormones, cortisol, and aldosterone.
  • Present in cell membranes.
  • Measured in blood as LDL (bad) and HDL (good) cholesterol.
• LDL (low-density lipoproteins): Transport fats from liver to body.
• HDL (high-density lipoproteins): Return fats to liver for processing.
• Balance between HDL and LDL is crucial for health.

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