Quick Revision Notes
Chapter 8 – Cell: The Unit of Life (Class 11 NCERT)
Read these bullet-style notes once, then close book and recite the headings aloud. That active
recall step is the real grade-booster.
1. Why Study Cells?
All living organisms are built of cells, the fundamental structural and functional units of
life [1] .
A single cell can perform – nutrition, respiration, growth, reproduction, excretion – so
“nothing less than a complete cell is alive” [1] .
2. Cell Theory (3 Sentences You Must Quote)
1. All living things are composed of cells and cell products [1] .
2. The cell is the basic unit of structure and function in organisms [1] .
3. New cells arise only from pre-existing cells (Virchow’s “Omnis cellula-e cellula”) [1] .
Remember: Schleiden + Schwann → Theory; Virchow → Added cell division.
3. Size & Shape Benchmarks
Cell type Size examples Shape examples
Mycoplasma 0.3 µm (smallest living) pleomorphic
Bacteria 1-5 µm bacillus, coccus, spirillum
RBC 7 µm biconcave disc
Nerve cell up to 1 m long branched [1]
Exam tip: MCQs often ask “smallest cell” or “largest isolated single cell – ostrich egg”.
4. Prokaryotic vs Eukaryotic Cells
Feature Prokaryote Eukaryote
Nucleus No true nucleus; naked circular DNA True nucleus with nuclear envelope [1]
Organelles No membrane-bound organelles Many membrane-bound organelles
Ribosome 70 S 80 S (70 S in mitochondria & chloroplasts) [1] [2]
Cell wall Peptidoglycan in bacteria Cellulose (plants) or absent (animals)
Chapter 8 – Cell: The Unit of Life (Class 11 NCERT)
Read these bullet-style notes once, then close book and recite the headings aloud. That active
recall step is the real grade-booster.
1. Why Study Cells?
All living organisms are built of cells, the fundamental structural and functional units of
life [1] .
A single cell can perform – nutrition, respiration, growth, reproduction, excretion – so
“nothing less than a complete cell is alive” [1] .
2. Cell Theory (3 Sentences You Must Quote)
1. All living things are composed of cells and cell products [1] .
2. The cell is the basic unit of structure and function in organisms [1] .
3. New cells arise only from pre-existing cells (Virchow’s “Omnis cellula-e cellula”) [1] .
Remember: Schleiden + Schwann → Theory; Virchow → Added cell division.
3. Size & Shape Benchmarks
Cell type Size examples Shape examples
Mycoplasma 0.3 µm (smallest living) pleomorphic
Bacteria 1-5 µm bacillus, coccus, spirillum
RBC 7 µm biconcave disc
Nerve cell up to 1 m long branched [1]
Exam tip: MCQs often ask “smallest cell” or “largest isolated single cell – ostrich egg”.
4. Prokaryotic vs Eukaryotic Cells
Feature Prokaryote Eukaryote
Nucleus No true nucleus; naked circular DNA True nucleus with nuclear envelope [1]
Organelles No membrane-bound organelles Many membrane-bound organelles
Ribosome 70 S 80 S (70 S in mitochondria & chloroplasts) [1] [2]
Cell wall Peptidoglycan in bacteria Cellulose (plants) or absent (animals)
