Biomolecules

Biomolecules are organic compounds essential for life processes.

Overview

graph TD
    A[Biomolecules] --> B[Carbohydrates]
    A --> C[Proteins]
    A --> D[Nucleic Acids]
    A --> E[Vitamins]
    B --> B1[Monosaccharides]
    B --> B2[Polysaccharides]
    C --> C1[Amino Acids]
    C --> C2[Structure]

Carbohydrates

General formula: Cₙ(H₂O)ₘ

Classification

Monosaccharides: Cannot be hydrolyzed further

• Glucose (C₆H₁₂O₆)
• Fructose (C₆H₁₂O₆)

Oligosaccharides: 2-10 monosaccharide units

• Sucrose (glucose + fructose)
• Maltose (glucose + glucose)
• Lactose (glucose + galactose)

Polysaccharides: Many monosaccharide units

• Starch, Cellulose, Glycogen

Glucose

Structure:

• Aldohexose (CHO at C1)
• 4 chiral centers → D-glucose
• Cyclic forms: α and β glucose

Reactions:

• Reduction → Sorbitol
• Oxidation → Gluconic acid (mild), Glucaric acid (strong)
• Acetylation → Penta-acetyl glucose

Reducing and Non-Reducing Sugars

Reducing: Have free aldehyde/ketone group (glucose, maltose)

Non-reducing: No free carbonyl group (sucrose)

Proteins

Amino Acids

General structure: H₂N-CHR-COOH

Essential: Cannot be synthesized by body (must be obtained from diet)

Properties:

• Amphoteric (can act as acid or base)
• Zwitterion form: ⁺H₃N-CHR-COO⁻
• Isoelectric point (pI): pH at which amino acid is neutral

Peptide Bond

Formed by condensation between -COOH and -NH₂ groups.

Protein Structure

Denaturation

Loss of secondary/tertiary structure due to:

• Heat
• pH change
• Heavy metals
• Organic solvents

Nucleic Acids

Components

DNA:

• Sugar: Deoxyribose
• Bases: A, G, C, T
• Double helix

RNA:

• Sugar: Ribose
• Bases: A, G, C, U
• Usually single strand

Base Pairing

• A = T (2 H-bonds)
• G ≡ C (3 H-bonds)

Central Dogma

DNA → RNA → Protein (replication) (transcription) (translation)

Vitamins

Water-Soluble: B complex, C

• Not stored in body
• Required regularly

Fat-Soluble: A, D, E, K

• Stored in fat tissues
• Excess can cause toxicity

Hormones

Chemical messengers produced by endocrine glands.

Types:

• Steroid hormones (cholesterol derivatives)
• Peptide hormones (amino acid chains)
• Amino acid derivatives

Practice Problems

1. How many chiral centers are present in glucose?

2. Explain why sucrose is a non-reducing sugar but maltose is reducing.

3. What happens when a protein is denatured?

Further Reading

• Nitrogen Compounds - Amines and amino acids
• Organic Principles - Basic organic chemistry