Chemistry Biomolecules JEE Syllabus

Biomolecules are the chemical foundation of life, governing processes like energy production, metabolism, and genetic inheritance through a highly organised system of organic molecules. This chapter stands out because core organic concepts such as functional groups, hydrogen bonding, and polymer formation directly explain biological behaviour.

Here, the focus shifts from reaction-based chemistry to structure–function relationships, where molecular structure determines biological role. Even small structural changes can lead to completely different properties, such as glucose and fructose having the same formula but different functions. For JEE, Biomolecules is a clear and scoring chapter with questions mainly based on classification, identification, and basic properties.

Classification of Biomolecules

Biomolecules are broadly classified based on their structure and function in living systems.

Main types:

• Carbohydrates: Primary source of energy in biological systems

• Proteins: Structural and functional molecules made of amino acids

• Lipids: Energy storage and membrane-forming molecules

• Nucleic acids: Genetic material (DNA and RNA)

• Vitamins: Essential micronutrients required in small amounts

• Enzymes: Biological catalysts that speed up reactions

Key idea:

Each class of biomolecule performs a specific biological role, and its structure directly determines function.

Carbohydrates

Carbohydrates are polyhydroxy aldehydes or ketones or compounds that yield them on hydrolysis.

Classification:

• Monosaccharides: Single sugar units (e.g., glucose, fructose)

• Disaccharides: Two sugar units (e.g., sucrose, maltose)

• Polysaccharides: Large polymeric sugars (e.g., starch, cellulose)

Important concept:

Glucose is an aldose, while fructose is a ketose, but both share the same molecular formula C₆H₁₂O₆.

Proteins and Amino Acids

Proteins are polymers of amino acids linked by peptide bonds.

Amino acids definition:

Organic compounds containing both an amino group (–NH₂) and a carboxyl group (–COOH).

Peptide bond:

Formed by a condensation reaction between the amino group and the carboxyl group with the loss of water.

General idea:

Amino acids exist as zwitterions in solution due to an internal acid-base reaction.

Protein structure levels:

• Primary: Sequence of amino acids

• Secondary: α-helix and β-pleated sheet

• Tertiary: 3D folding of polypeptide chain

• Quaternary: Arrangement of multiple polypeptide chains

Lipids

Lipids are non-polar biomolecules that are insoluble in water but soluble in organic solvents.

Types:

• Fats and oils (triglycerides)

• Phospholipids (cell membrane structure)

• Steroids (cholesterol and hormones)

Key idea:

Lipids are not true polymers but are essential for energy storage and membrane structure.

Nucleic Acids

Nucleic acids store and transfer genetic information.

Types:

• DNA: Deoxyribonucleic acid

• RNA: Ribonucleic acid

Basic unit:

Nucleotide, which consists of:

• Nitrogenous base

• Pentose sugar

• Phosphate group

Key function:

DNA stores the genetic code, while RNA helps in protein synthesis.

Enzymes

Enzymes are biological catalysts that increase the rate of biochemical reactions without being consumed.

Key properties:

• Highly specific in action

• Function optimally at specific temperature and pH

• Can be denatured under extreme conditions

Important idea:

Enzyme activity depends on the shape of its active site.

Vitamins

Vitamins are organic compounds required in small quantities for normal metabolic function.

Types:

• Fat-soluble: A, D, E, K

• Water-soluble: B-complex and C

Deficiency of vitamins leads to specific diseases such as scurvy, rickets, and night blindness.

Biomolecules connect chemistry with biology by explaining how molecular structure controls life processes. For JEE, this chapter is mainly factual and conceptual, making it an easy scoring area if revised properly with a clear understanding of structures and functions.