20. Classification of lipids. Hydrolyzable lipids-examples. Chemical aspects of biological oxidation of fats and oils. Phospholipids – types and biological significance.

Lipids - definition and classifications.

• Lipids are a diverse group of biomolecules united more by their physical properties (like being oily and water-fearing) than by their chemical structures. They play crucial roles in our bodies, from building cell walls to storing energy.
• classifications:
• By Structure:
• Simple Lipids: Think fats and waxes - they're just fatty acids hanging out with an alcohol (fats) or a long hydrocarbon chain (waxes).
• Complex Lipids: These are more intricate, like phospholipids (key players in cell membranes) and glycolipids (involved in cell signaling).
• Derived Lipids: Fatty acids themselves, along with hormones and steroids (like cholesterol), fall into this category.
• By Reaction with Water:
• Saponifiable Lipids: These can be broken down with bases (like lye) into soap - think fatty acids and triglycerides (fats).
• Non-saponifiable Lipids: Water and soap won't touch these - they include sterols (like cholesterol) and fat-soluble vitamins (A, D, E, and K).
• By Biosynthesis (How They're Made):
• Fatty Acyl Group: This group includes fatty acids, the building blocks for many other lipids, as well as fats, phospholipids, glycolipids, and even waxes.
• Isoprene: This building block forms the backbone of terpenes (found in essential oils), fat-soluble vitamins, and steroids.