Chapter 7 – Biomolecules (JEE Chemistry)
1. Introduction to Biomolecules
Biomolecules are naturally occurring organic compounds found in living organisms.
They are essential for growth, metabolism, and maintenance of life.
Main classes of biomolecules:
- Carbohydrates
- Proteins
- Enzymes
- Vitamins
- Nucleic Acids
2. Carbohydrates
Carbohydrates are polyhydroxy aldehydes or ketones, or substances that give these on hydrolysis.
General formula: $C_x(H_2O)_y$
Classification of Carbohydrates
| Type | Examples |
|---|---|
| Monosaccharides | Glucose, Fructose |
| Disaccharides | Sucrose, Maltose |
| Polysaccharides | Starch, Cellulose, Glycogen |
3. Monosaccharides
Monosaccharides cannot be hydrolysed further.
They are the simplest carbohydrates.
Glucose: $C_6H_{12}O_6$
Glucose is an aldohexose and exists mainly in cyclic form.
4. Disaccharides
Disaccharides give two monosaccharide units on hydrolysis.
| Disaccharide | Composition |
|---|---|
| Sucrose | Glucose + Fructose |
| Maltose | Glucose + Glucose |
| Lactose | Glucose + Galactose |
5. Polysaccharides
Polysaccharides contain many monosaccharide units linked together.
- Starch – plant storage
- Glycogen – animal storage
- Cellulose – structural material
6. Proteins
Proteins are polymers of amino acids linked by peptide bonds.
Peptide bond: $-CO-NH-$
Amino Acids
General structure: $H_2N-CH(R)-COOH$
Amino acids are zwitterions in aqueous solution.
7. Levels of Protein Structure
| Level | Description |
|---|---|
| Primary | Sequence of amino acids |
| Secondary | α-helix and β-sheet |
| Tertiary | 3D folding |
| Quaternary | Multiple polypeptide chains |
8. Enzymes
Enzymes are biological catalysts that speed up biochemical reactions.
- Highly specific
- Work best at optimum temperature and pH
9. Vitamins
Vitamins are organic compounds required in small amounts for normal growth.
| Type | Examples |
|---|---|
| Fat soluble | A, D, E, K |
| Water soluble | B-complex, C |
10. Nucleic Acids
Nucleic acids are polymers of nucleotides.
They store and transmit genetic information.
Types:
- DNA – Deoxyribonucleic Acid
- RNA – Ribonucleic Acid
Nucleotide = Base + Sugar + Phosphate
11. Important JEE Points
- Glucose is reducing sugar
- Sucrose is non-reducing sugar
- Enzymes are proteins
- Deficiency of vitamins causes diseases
12. Final Revision Checklist
You are ready for the exam if you can:
- Classify carbohydrates correctly
- Identify reducing and non-reducing sugars
- Explain protein structure levels
- Differentiate DNA and RNA
- Recall vitamin types and functions