Lecture Notes: Lipids

Introduction to Lipids

Lipids are classified into two main categories:
- Hydrolyzable Lipids: Can be broken down into smaller sections.
- Non-Hydrolyzable Lipids: Cannot be broken down into smaller sections.
Triglycerol is a common and abundant lipid, mainly used for energy storage.

Definition: Hydrolyzable lipids containing a phosphorus atom in the form of a phosphodiester bond.
- Derived from phosphoric acid (H₃PO₄).
- Phosphorus can bond more than four times, unlike carbon.
- Formed via dehydration reaction into phosphodiesters.
Structure:
- Phospholipids have a polar phosphodiester head and non-polar fatty acid tails.
- Leads to the formation of the phospholipid bilayer in cell membranes.
- Separate the inside of the cell from the outside, creating distinct fluid compartments.

Another type of hydrolyzable lipid involving a phosphodiester unit.
Base of amino alcohol sphingosine, which is a high molecular weight alcohol with lipid characteristics.
Function:
- Present in nerve cells, contributing to the insulation of nerve axons through high sphingolipid concentration in myelin.

Hydrolyzable esters made of high molecular weight alcohol and fatty acids.
Structure:
- Form esters with long carbon chains, resulting in two non-polar sections.
- Highly hydrophobic due to these non-polar sections.
Role:
- Serve as a barrier against water, found in nature on leaves and used on cars.

All hydrolyzable lipids contain ester bonds that can be broken down through hydrolysis reactions:
- Phospholipids: Hydrolyze ester bonds linking phosphorus.
- Sphingolipids: Ester group can be broken.
- Waxes: Ester bonds between long chains are hydrolyzable.

Hydrolyzable lipids can be broken down into smaller units, providing both structural and storage functions in biological systems.