Triglycerides and Phospholipids

Introduction

• Lipids such as triglycerides and phospholipids are essential biological molecules.
• Both contain a glycerol molecule (three-carbon compound) and fatty acids.

Structure

Triglycerides

• Composed of:
  • Glycerol molecule.
  • Three fatty acid chains.
  • Linked by three condensation reactions, forming three ester bonds.
• Saturated vs. Unsaturated Fatty Acids:
  • Saturated: Only single bonds between carbons, fully saturated with hydrogen.
  • Unsaturated: At least one double bond between carbons, not fully saturated with hydrogen.

Phospholipids

• Composed of:
  • Glycerol molecule.
  • Two fatty acid chains.
  • One phosphate group (replaces the third fatty acid chain).
• Formation involves condensation reactions, forming two ester bonds.

Properties

Triglycerides

• Energy storage:
  • High ratio of carbon-hydrogen bonds, storing a lot of energy.
  • High ratio of hydrogen to oxygen enables it to act as a metabolic water source.
• Hydrophobic nature:
  • Insoluble in water, doesn't affect water potential or osmosis.
• Low density:
  • Allows storage without making the animal too heavy.

Phospholipids

• Hydrophilic head:
  • Phosphate group carries a negative charge, interacts with water.
• Hydrophobic tails:
  • No charge, repels water but interacts with lipids.
• Arrange in a bilayer when in water:
  • Structural basis of cell membranes and organelles.
  • Polar nature due to differing charged regions.

Testing for Lipids

Emulsion Test

• Procedure:
  1. Dissolve sample in ethanol.
  2. Add distilled water and shake.
• Positive result: White emulsion forms, not a precipitate.

Conclusion

• Understand the structure and formation of triglycerides and phospholipids.
• Know their properties, functions, and the emulsion test for identifying lipids.
• Key to biological processes and cellular structures.

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