B1.1.9 Formation of triglycerides and phospholipids by condensation reactions Notes

Triglycerides: Energy Storage Molecules

Building Blocks

1. Glycerol: A three-carbon molecule with three hydroxyl (–OH) groups.
2. Fatty Acids: Long hydrocarbon chains ending in a carboxyl (–COOH) group.
   1. Saturated (no C=C double bonds), monounsaturated (one double bond), or polyunsaturated(multiple double bonds).

Formation via Condensation

1. Each fatty acid reacts with a hydroxyl on glycerol, releasing water (H₂O) and forming an ester bond.
2. Glycerol can bond with three fatty acids → triglyceride (3 ester bonds, 3 H₂O molecules released).
3. The carboxyl and hydroxyl groups are consumed, making the resulting triglyceride hydrophobic.

Properties and Functions

1. Hydrophobic: Insoluble in water, forming compact droplets for energy storage.
2. Energy Density: Higher energy content per gram than carbohydrates.
3. Insulation and Protection: In animals, stored in adipose tissue to cushion organs and retain heat.

Condensation Reactions in Lipid Formation

1. Water Release: Each ester bond formed expels 1 H₂O molecule.
2. Energy Requirement: Formation typically needs energy input (e.g., from ATP) to build covalent bonds.
3. Covalent Bond Stability: Ester bonds provide the robust link between glycerol and fatty acids (or phosphate group).

Importance of Triglycerides and Phospholipids

1. Triglycerides
   1. Long-Term Energy Storage: Higher energy density vs. carbohydrates.
   2. Protection/Insulation: Fat deposits help organisms maintain thermal balance and protect organs.
2. Phospholipids
   1. Membrane Formation: Essential for cell boundary and compartmentalization.
   2. Membrane Fluidity: Adjusted by fatty acid saturation, key to proper cellular function.

Phospholipids Are The Building Blocks of Membranes

1. Phospholipids, another class of lipids, are critical for forming cell membranes.
2. They share similarities with triglycerides but have a distinct feature: one fatty acid chain is replaced by a phosphate group.

The Structure of Phospholipids

1. Glycerol Backbone: Like triglycerides, phospholipids have a glycerol molecule.