The Fundamental Unit of Life Class 9 Science — Revision Notes
This chapter introduces cells as basic unit of life. Students learn about cell structure, differences between plant and animal cells, and cell organelles.
TL;DR: This chapter introduces cells as basic unit of life. Students learn about cell structure, differences between plant and animal cells, and cell organel…
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This chapter introduces cells as basic unit of life. Students learn about cell structure, differences between plant and animal cells, and cell organelles.
Cell Basics
- Cell is smallest unit of life
- All living organisms made of one or more cells
- Robert Hooke discovered cells in cork tissue
- Schleiden and Schwann proposed cell theory
Cell Membrane
- Cell membrane is selectively permeable boundary of cell
- Regulates what enters and exits cell
- Made of phospholipid bilayer with embedded proteins
- Controls osmosis and transport of substances
Prokaryotic vs Eukaryotic Cells
- Prokaryotic: no membrane-bound nucleus (bacteria, archaea)
- Eukaryotic: membrane-bound nucleus and organelles (plants, animals, fungi)
- Prokaryotic simpler, smaller than eukaryotic
- Nucleoid region in prokaryotes contains genetic material
Cell Organelles
- Nucleus: contains DNA, controls cell functions
- Mitochondria: site of aerobic respiration (powerhouse of cell)
- Chloroplasts: photosynthesis in plant cells
- Endoplasmic reticulum: protein and lipid synthesis
- Golgi apparatus: packaging and transport of molecules
- Vacuole: storage in plant cells (large), animal cells (small)
Key Terms
- Cell: Basic structural and functional unit of all living organisms
- Organelle: Membrane-bound structure inside cell performing specific functions
- Nucleus: Membrane-bound organelle containing genetic material
Frequently Asked Questions
What is cell theory?
Cell theory states: (1) All living organisms are made of cells, (2) Cell is basic unit of life, (3) All cells come from pre-existing cells.
Why is mitochondria called powerhouse of cell?
Mitochondria is site of aerobic respiration where glucose is broken down to release energy in the form of ATP molecules.
More Class 9 Science Revision Notes
- Matter in Our Surroundings
- Is Matter Around Us Pure
- Atoms and Molecules
- Structure of the Atom
- Tissues
- Motion
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