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Cell: The Unit of Life

NCERT Class 11 Biology Chapter 8

Cell: The Unit of Life for Class 11 Biology and NEET: cell theory, prokaryotic and eukaryotic cells, the cell membrane, cell organelles and the nucleus.

5 topics Updated 8 Nov 2026

For: Class 11 and NEET

In the syllabus: NEET Class 11 syllabus

With your textbook

NCERT Biology (Class 11), Chapter 8 “Cell: The Unit of Life”, reprint 2026-27.

Open the official NCERT chapter (PDF, 7.0 MB, ncert.nic.in)

Checked on 19 Oct 2026.

Learn in this order

  1. What is a cell?

    What is a cell, for Class 11 Biology and NEET: why it is the basic unit of life, unicellular vs multicellular, and who discovered the cell and the nucleus.

    NCERT Section 8.1 7 min read 4 solved examples 7 practice questions

  2. Cell theory

    Cell theory for Class 11 Biology and NEET: who proposed it, Virchow’s omnis cellula e cellula, the modern cell theory and its exceptions.

    NCERT Section 8.2 8 min read 4 solved examples 7 practice questions

  3. An overview of the cell

    Prokaryotic and eukaryotic cells for Class 11 Biology and NEET: how they differ, cytoplasm, membrane-bound organelles, and the smallest and largest cells.

    NCERT Section 8.3 10 min read 5 solved examples 8 practice questions

  4. Prokaryotic cells

    Prokaryotic cell structure for Class 11 Biology and NEET, with a labelled diagram: cell envelope, Gram positive vs negative, mesosomes, plasmids, pili.

    NCERT Section 8.4 13 min read 5 solved examples 8 practice questions

  5. Eukaryotic cells and cell organelles

    Eukaryotic cell organelles and their functions for Class 11 Biology and NEET: plant vs animal cell, fluid mosaic model, 70S vs 80S, with diagrams.

    NCERT Section 8.5 24 min read 6 solved examples 10 practice questions

Key formulas in this chapter

What is a cell?

  • cell: fundamental structural and functional unit of life
  • unicellular: one cell performs essential life functions
  • multicellular: many cells
  • Leeuwenhoek: first live cell; Robert Brown: nucleus

Cell theory

  • 1838 Schleiden: plants made of cells
  • 1839 Schwann: plasma membrane; plant–animal wall comparison
  • 1855 Virchow: omnis cellula e cellula
  • tenet 1: organisms made of cells and products of cells
  • tenet 2: all cells arise from pre-existing cells

Overview of the cell

  • eukaryotic: membrane-bound nucleus and organelles
  • prokaryotic: no membrane-bound nucleus or organelles
  • ribosomes: no membrane; present in both major cell types
  • smallest cells: mycoplasmas, 0.3 µm
  • largest isolated single cell: ostrich egg
  • human RBC: about 7.0 µm across

Prokaryotic cells

  • bacterial shapes: bacillus, coccus, vibrio, spirillum
  • cell envelope: glycocalyx, cell wall, plasma membrane
  • glycocalyx: slime layer (loose) or capsule (thick, tough)
  • flagellum: filament, hook, basal body
  • prokaryotic ribosome: 70S, of 50S and 30S subunits (S values do not add)
  • inclusion bodies: phosphate, cyanophycean, glycogen granules

Eukaryotic cells

  • endomembrane system: ER, Golgi complex, lysosomes, vacuoles
  • ribosomes: 80S (60S, 40S) cytoplasm; 70S (50S, 30S) prokaryotes, mitochondria, chloroplasts
  • mitochondrion: 0.2–1.0 µm wide (average 0.5), 1.0–4.1 µm long
  • chloroplast: 5–10 µm long, 2–4 µm wide
  • axoneme: 9 + 2 (nine doublets, a central pair)
  • centriole: nine triplets, cartwheel
  • perinuclear space: 10–50 nm
  • chromosome types: metacentric, sub-metacentric, acrocentric, telocentric

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