Introduction to Lipids and Classification of Lipids

INTRODUCTION TO LIPIDS

What are lipids? Where can they be found? How do we recognise them? How are lipids classified? What are the components (building blocks) of lipids? What are the important lipids in medicine and healthy living?

Biological molecules that are insoluble in aqueous solutions (water-based media) but are soluble in organic solvents are classified as LIPIDS. Lipids are a diverse group of biological substances which are made up of primarily non-polar functional groups. Lipids include oils (eg cooking oil, ghee, butter), waxes (candles, beeswax, car polish, earwax/tahi telinga), phospholipids (eg soy lecithin, used in creamers, used in instant milk, used in instant drinks), steroids (body builders and athletes consume them), sterols (eg cholesterol), terpenes (eg beta-carotene, the orange stuff in carrots, the red stuff in tomatoes) and many others. There are some 7-9 classes of lipids, depending on how we organise them.


CLASSIFICATION OF LIPIDS

1. Lipids are divided into 2 types based on their hydrolysis reactions/ability to be hydrolysed - Simple Lipids and Complex Lipids
2. Simple Lipids are classed as Terpenes and Steroids & Sterols. Simple Lipids are not hydrolysable.
3. Free Fatty Acids (FFA) are esterified to form larger molecules grouped as Complex Lipids. 
4. Complex Lipids include Waxes, Triglycerides, Glycerophospholipids and Eicasanoids. Complex Lipids contain a component called Fatty Acids. All components of Complex Lipids are hydrolysable to yield the free components forms.
5. Esterified complex lipids consist of 1 or more components which are hydrolysable into simple components.
6. The common building block for most of the different types of lipids is the fatty acids.
7. Fatty acids are composed of a chain on methylene groups (-CH2-) with a carboxyl functional group (-COOH) at one end. 
8. Lipids differ mainly in the nature of the fatty acid chains.