Biomolecules

Living organisms are made up of complex chemical compounds called biomolecules. Whether it is the rice you eat for dal bhat, the muscles in your body, or the DNA that carries your genetic information -- they are all biomolecules. Let us explore the four major types.

Carbohydrates

Carbohydrates are compounds of carbon, hydrogen, and oxygen with the general formula Cn(H₂O)n. They are the primary energy source for living organisms.

Classification:

• Monosaccharides (simple sugars): Glucose (C₆H₁₂O₆), fructose, galactose
• Disaccharides (two sugars joined): Sucrose (glucose + fructose), lactose, maltose
• Polysaccharides (many sugars): Starch (energy storage in plants), glycogen (energy storage in animals), cellulose (structural in plant cell walls)

Function: Energy source (glucose), structural support (cellulose), energy storage (starch, glycogen)

Proteins

Proteins are polymers of amino acids linked by peptide bonds. There are 20 different amino acids.

Structure levels:

• Primary: Sequence of amino acids
• Secondary: Alpha helix or beta sheet (held by hydrogen bonds)
• Tertiary: 3D folding of the polypeptide
• Quaternary: Multiple polypeptide chains together

Functions: Enzymes (catalysts), structural (keratin in hair, collagen in skin), transport (haemoglobin), defence (antibodies), hormones (insulin)

Lipids

Lipids are fats and oils -- esters of fatty acids and glycerol. They are hydrophobic (water-insoluble).

Types:

• Saturated fats: No double bonds in fatty acid chains (solid at room temperature, e.g., ghee/butter)
• Unsaturated fats: One or more double bonds (liquid at room temperature, e.g., mustard oil)

Functions: Energy storage (most efficient -- 9 kcal/g vs 4 kcal/g for carbs), insulation, cell membrane structure (phospholipids), hormone production

Nucleic Acids

DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid) carry genetic information.

• DNA: Double-stranded helix. Sugar: deoxyribose. Bases: A, T, G, C. Stores genetic information.
• RNA: Single-stranded. Sugar: ribose. Bases: A, U, G, C. Helps in protein synthesis.

Base pairing rules: A-T (in DNA) or A-U (in RNA), G-C

Enzymes

Enzymes are biological catalysts (mostly proteins) that speed up chemical reactions without being consumed.

• Lock and key model: The enzyme's active site has a specific shape that fits only its substrate
• Enzymes are specific: each enzyme catalyzes only one type of reaction
• Affected by temperature and pH (optimal conditions exist)

Nepal Connection

Nepal's diverse cuisine -- dal (proteins), bhat/rice (carbohydrates), tarkari with mustard oil (lipids) -- provides all essential biomolecules. Understanding nutrition helps address malnutrition challenges in rural Nepal.

Key Takeaways

• Carbohydrates: primary energy source (glucose, starch)
• Proteins: made of amino acids, serve many functions (enzymes, structural)
• Lipids: energy storage, cell membranes, insulation
• Nucleic acids (DNA/RNA): carry genetic information
• Enzymes: biological catalysts with specific active sites