Lipids - Triglycerides and Phospholipids

Characteristics of Lipids

• Composed of carbon, hydrogen, and oxygen.
• Lower oxygen-to-carbon and hydrogen ratio compared to carbohydrates.
• Insoluble in water and organic solvents like alcohol and acetone.

Main Groups of Lipids

• Triglycerides (fats and oils)
• Phospholipids
• Waxes

Triglycerides

• Comprised of one glycerol molecule linked to three fatty acids.

Role of Lipids as an Energy Source

• Fatty acids have long hydrocarbon tails rich in chemical energy.
• Lipids yield more than double the energy of carbohydrates per mass and produce valuable water upon oxidation.

Role of Lipids in Waterproofing

• Large nonpolar molecules, lipids are effective for waterproofing in plants and insects.
• Waxy lipid cuticles help conserve water.

Role of Lipids in Insulation

• Serve as poor conductors of heat, aiding in heat retention under the skin.

Electrical Insulation

• Lipids form myelin sheaths around neuron axons, preventing premature conduction of nerve impulses.

Protection

• Fat surrounding vital organs acts as a shock absorber.

Insolubility of Lipids

• Lipids do not dissolve in water, preventing osmotic pressure that could cause cells to swell.

Hormone Production

• Lipids are essential for the formation of steroid hormones, including oestrogen and certain plant growth hormones.

State of Fats vs. Oils

• Fats are solid at room temperature (10-20°C), in contrast to liquid oils.

Type of Bond in Triglycerides

• Fatty acids bond to glycerol via ester bonds.

Chemical Processes

• Condensation Reaction: Molecules combine to form a complex one, typically releasing water.
• Hydrolysis: Larger molecules break down into smaller units with the addition of water.

Variations in Properties of Fats and Oils

• While glycerol is consistent in all triglycerides, differences arise from variations in fatty acids; over 70 distinct fatty acids exist.

Saturated Fatty Acids

• Contain maximum hydrogen atoms, no carbon double bonds.

Unsaturated Fatty Acids

• Mono-unsaturated Fatty Acids: Feature one carbon double bond.
• Polyunsaturated Fatty Acids: Contain multiple carbon double bonds, causing bends in structure.

Effect of Double Bonds

• The presence of double bonds prevents tight packing of molecules, resulting in liquids at room temperature.

Phospholipids

• Composed of two fatty acids and one phosphate group, exhibiting hydrophilic properties.

Structure of Phospholipids

• Hydrophilic "Head": Interacts with water.
• Hydrophobic "Tail": Repels water and mixes with fats.

Polar Molecules

• Exhibit dual properties (polar ends), leading phospholipids to orient with heads near water and tails away from it.

Test for Lipids

• Procedure involves using ethanol to dissolve lipids, followed by adding water to observe for a cloudy white emulsion.

Cloudy White Color in Lipid Test

• Result of lipid dispersion in water, creating an emulsion that refracts light, giving a cloudy appearance.