Water, Lipids, and Carbohydrates: Essential Biochemicals

Water Properties

• Water behaves like a dipole: OH bonds shift to oxygen, creating partial charges.
• Hydrogen bonds form between water molecules.
• Water is a great solvent due to hydration atmospheres.

Osmotic Pressure

• Hypertonic: Increased osmotic pressure, higher concentration.
• Hypotonic: Lower osmotic pressure, lower concentration.

Disaccharide Characteristics

1. Hydrolyzable into subunits.
2. Sweet taste.
3. Crystallizable.
4. Water-soluble.
5. No reducing power loss.

Hemiacetal Linkage

Cellulose

Cellulose consists of parallel chains joined by hydrogen bonds, forming microfibrils and fibers. This structure makes cellulose water-insoluble and rigid, providing structural support in plants. Humans and animals lack enzymes to break down cellulose, but some organisms (e.g., termites, ruminants) have symbiotic microorganisms with cellulase.

Fiber-rich foods aid digestion, promote peristalsis, and prevent constipation. They also cleanse the colon and may help prevent colon cancer.

Lipid Classification

Lipids are classified into saponifiable and unsaponifiable lipids.

• Saponifiable lipids include:
  1. Glycerides
  2. Complex lipids
  3. Waxes
• Unsaponifiable lipids include:
  1. Terpenes
  2. Steroids

Fatty Acid Properties

1. Fatty acids have polar (COOH group) and apolar (hydrocarbon chain) regions.
2. Melting point variations:
   • Longer chains have higher melting points due to increased Van der Waals forces.
   • Unsaturated acids have lower melting points because double bonds hinder Van der Waals forces.

Glycerides

Classification: Monoacylglycerides (one fatty acid), diacylglycerides (two fatty acids), and triacylglycerides (three fatty acids).

Phospholipids

Phospholipids have a phosphate group linked to alcohol. Types include:

a) Glycerophospholipids: Glycerol, fatty acids, and a phosphate group (e.g., lecithin, cephalin).

b) Sphingophospholipids: Sphingosine, fatty acids, a phosphate group, and another component (R).

Biological Functions of Complex Lipids

Form part of biological membranes.

Biological Functions of Waxes

Structural and protective functions (e.g., plant cuticles, bird plumage, beeswax).

Terpenes

Examples include:

• Vitamin A (vision)
• Carotenes and xanthophylls (photosynthesis)
• Vitamin K
• Rubber

Biological Functions of Lipids

1. Energy reserves
2. Structural components
3. Protection
4. Thermal insulation
5. Pigments
6. Vitamins and hormones