23. Lipids – classification. Lipids digestion – enzymes. Composition, origin and functions of the lipoprotein complexes. Receptors, apolipoproteins, enzymes of the lipoprotein metabolism. Familial hypercholesterolemia.

Introduction

Lipids are a broad and diverse group of biological molecules characterized by their solubility in nonpolar solvents and general insolubility in water.

This class of compounds is crucial in numerous biological functions and processes, and their hydrophobic (water-fearing) nature plays a fundamental role in their biological activities and structural functions.

Fundamental Properties and Functions of Lipids

• Hydrophobic Nature: The majority of lipids contain long chains of hydrocarbons which do not interact favourably with water molecules, leading to their hydrophobic characteristics. This property defines their role in biological membranes and energy storage.
• Structural Components: Lipids form essential structural components of all cell membranes, creating a hydrophobic barrier that separates and protects the cellular interior from the external environment.
• Energy Storage: Lipids serve as a compact and rich source of energy. They provide more than twice the energy per gram as compared to carbohydrates and proteins, making them efficient long-term energy storage molecules.
• Signaling Molecules: Many lipids also play roles in signalling pathways. They can act as hormones (like steroid hormones) or as secondary messengers in signal transduction pathways.
• Protective Role: In many organisms, fats serve as insulation from the environment and as cushions to protect vital organs.