Lipids and Circulatory System

Lipids play various roles in biological systems:

1. Phospholipids: Form cell membranes
2. Cholesterol: Important for cell membranes, sex hormones, and bile salts
3. Triglycerides: Energy storage, insulation, protection, buoyancy, and hormone synthesis

Highlight: The presence of double bonds in unsaturated fats creates "kinks" in the fatty acid chains, affecting their physical properties such as melting point.

The circulatory system is essential for multicellular organisms:

• Diffusion is insufficient for large organisms
• Blood carries substances throughout the body
• The heart pumps blood through the circulatory system

Definition: Diffusion - The movement of particles from an area of high concentration to an area of low concentration.

This section of the AS biology unit 1 revision notes lifestyle health risk pdf provides a comprehensive overview of key biological molecules and systems, essential for understanding the foundations of biology at the AS level.

Polysaccharides and Lipids in Biology

Polysaccharides are long chains of glucose molecules with specific structures and functions:

1. Glycogen:

   • Found in muscle and liver cells for energy storage
   • Made of alpha glucose units with 1,4 and 1,6 links, forming branches
   • Insoluble and compact

2. Starch:

   • Found in plant cells for energy storage
   • Composed of amylose (long chain with 1,4 links) and amylopectin (similar to glycogen)
   • Insoluble and compact

3. Cellulose:

   • Main component of plant cell walls
   • Made from beta glucose units
   • Forms strong fibrils due to hydrogen bonding between chains

Definition: Condensation reaction - A chemical reaction in which two molecules combine to form a larger molecule, releasing water in the process.

Lipids, particularly triglycerides, are another important class of biomolecules:

• Composed of carbon, hydrogen, and oxygen
• Insoluble in water
• Formed by condensation of glycerol and three fatty acids
• Used for long-term energy storage and insulation

Vocabulary: Ester bond - A chemical bond formed between a fatty acid and glycerol in triglycerides.

Fatty acids can be:

• Saturated (no double bonds)
• Monounsaturated (one double bond)
• Polyunsaturated (multiple double bonds)

Example: Olive oil contains monounsaturated fats, while fish oils are rich in polyunsaturated fats.