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Syllabus
🩺 NEET UG
Subject:Biology Syllabus

Biomolecules

Syllabus Unit: Cell Structure and Function

Why it matters

Chapter overview

Every structure and reaction inside a cell is built from a small set of chemical building blocks — carbohydrates and lipids for energy and membranes, proteins folded into working machines, enzymes that make life's reactions fast enough to matter, and nucleic acids that store the instructions. This topic works through each biomolecule class with its real chemical identity — ring structures, peptide bonds, active sites, purines and pyrimidines — the level of detail NEET's biochemistry questions demand.

Biology Syllabus Cell Structure and Function 15% weightage
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MonosaccharidesGlucose, fructose — single units
OligosaccharidesSucrose, maltose — 2-10 units
PolysaccharidesStarch, glycogen, cellulose

1Carbohydrates & Lipids

Carbohydrates are the cell's primary fuel and structural fibre, while lipids form membranes and the body's densest energy store.

Learning Objectives

  • Classify carbohydrates as monosaccharides, oligosaccharides and polysaccharides with an example of each.
  • Distinguish a glycosidic bond and explain how it links monosaccharides into polymers.
  • Differentiate storage polysaccharides (starch, glycogen) from structural ones (cellulose, chitin).
  • Classify lipids as simple (fats/oils), compound (phospholipids) and derived (steroids, waxes).

Key Terms

MonosaccharideThe simplest carbohydrate unit (e.g. glucose, fructose, ribose) that cannot be hydrolysed into a simpler sugar.
Glycosidic BondThe covalent bond formed between two monosaccharide units via a condensation reaction, releasing water, linking sugars into oligo- and polysaccharides.
PolysaccharideA long polymer of many monosaccharide units, functioning as either energy storage (starch, glycogen) or structural support (cellulose, chitin).
PhospholipidAn amphipathic lipid with a hydrophilic phosphate head and two hydrophobic fatty acid tails; the fundamental building block of the cell membrane bilayer.

**Carbohydrates** are the most abundant biomolecules by mass in most organisms, and are classified by size: monosaccharides (single sugar units), oligosaccharides (2-10 units), and polysaccharides (long chains of hundreds to thousands of units).

Carbohydrate classes

  • Monosaccharides — glucose and fructose (hexoses, C6), ribose and deoxyribose (pentoses, C5) — cannot be broken down further by hydrolysis.
  • Oligosaccharides — e.g. sucrose (glucose + fructose), maltose (glucose + glucose) — 2 to 10 monosaccharides joined by glycosidic bonds.
  • Polysaccharides — starch and glycogen (energy storage in plants and animals respectively), cellulose (plant cell wall, structural), chitin (insect exoskeleton/fungal cell wall, structural).
Key PointStarch, glycogen and cellulose are all polymers of glucose — they differ only in the type of glycosidic bond and branching pattern, which is exactly why NEET tests them as a 'same monomer, different bond' comparison.

Lipid classes

  • Simple lipids — fats and oils, formed by esterifying glycerol with three fatty acids (triglycerides); fats are solid at room temperature (saturated), oils are liquid (unsaturated).
  • Compound lipids — phospholipids, with a phosphate-containing hydrophilic head and hydrophobic fatty acid tails, forming the bilayer of every cell membrane.
  • Derived lipids — steroids (e.g. cholesterol, steroid hormones) and waxes; built from a different core structure but grouped with lipids for their hydrophobic character.
Glycerol + 3 Fatty acids → (esterification, -3 H2O) → Triglyceride (fat/oil)