Class 9 Science MCQ Test – Fundamental Unit of Life : CELL (Chapter 5) | Full Chapter Test
Class 9 Science – Chapter: Fundamental Unit of Life (Cell)
These notes are designed for CBSE, GSEB and foundation students. It includes detailed theory, diagrams explanation, functions and exam-oriented concepts.
1. Discovery of Cell
The cell was first discovered by Robert Hooke (1665) while observing a thin slice of cork under a microscope.
- He saw small box-like compartments and named them "cells".
- Later, Anton van Leeuwenhoek observed living cells.
- Cell Theory was given by Schleiden and Schwann.
Cell Theory States:
- All living organisms are made up of cells.
- Cell is the basic structural and functional unit of life.
- All cells arise from pre-existing cells (Virchow).
2. What is a Cell?
A cell is the smallest unit of life capable of performing all vital functions such as respiration, digestion, and reproduction.
Types of Organisms:
- Unicellular: Made of single cell (Amoeba, Paramecium)
- Multicellular: Made of many cells (Humans, Plants)
3. Shape and Size of Cells
- Cells vary in shape: round, oval, elongated, irregular
- Size ranges from microscopic to visible (e.g., Ostrich egg)
- Shape depends on function
Examples:
- Neuron → long for transmission
- RBC → biconcave for oxygen transport
- Muscle cell → elongated for contraction
4. Cell Structure
A cell consists of three main parts:
- Cell Membrane (Plasma Membrane)
- Cytoplasm
- Nucleus
5. Cell Membrane (Plasma Membrane)
It is the outermost covering of the cell.
- Made of lipids and proteins
- Provides shape and protection
- Selectively permeable → allows some substances to pass
Transport Across Membrane:
- Diffusion: Movement from high concentration to low concentration
- Osmosis: Movement of water through semi-permeable membrane
Types of Solutions:
- Hypotonic: Cell swells
- Hypertonic: Cell shrinks
- Isotonic: No change
6. Cell Wall (Only in Plants)
- Present outside plasma membrane
- Made of cellulose
- Provides rigidity and protection
- Prevents bursting of cell
7. Cytoplasm
Cytoplasm is the jelly-like substance present between nucleus and cell membrane.
- Contains cell organelles
- Site of metabolic reactions
8. Cell Organelles
1. Nucleus
- Controls all activities of cell
- Contains genetic material (DNA)
- Surrounded by nuclear membrane
2. Endoplasmic Reticulum (ER)
- Rough ER: Protein synthesis
- Smooth ER: Lipid synthesis
3. Golgi Apparatus
- Packaging and transport of materials
- Secretion of substances
4. Mitochondria
- Known as Powerhouse of the cell
- Produces energy (ATP)
5. Ribosomes
- Site of protein synthesis
6. Lysosomes
- Contain digestive enzymes
- Called "Suicide bags"
7. Vacuoles
- Storage of water, food, waste
- Large in plant cells
8. Plastids (Plant Cells)
- Chloroplast: Photosynthesis
- Chromoplast: Colour
- Leucoplast: Storage
9. Difference Between Plant Cell and Animal Cell
- Plant cell → Cell wall present | Animal cell → Absent
- Plant cell → Plastids present | Animal cell → Absent
- Plant cell → Large vacuole | Animal cell → Small/absent
- Plant cell → Fixed shape | Animal cell → Irregular shape
10. Prokaryotic vs Eukaryotic Cells
- Prokaryotic: No nucleus (Bacteria)
- Eukaryotic: True nucleus present (Plants, Animals)
Key Differences:
- Prokaryotes → Simple structure
- Eukaryotes → Complex structure
- Prokaryotes → No membrane-bound organelles
- Eukaryotes → Organelles present
⬇️ Attempt the test given below after revising these notes
Class 9 Science
Chapter: Fundamental Unit of Life (Cell) | MCQ Test
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Class 9 Science Chapter: Fundamental Unit of Life (Cell)
The cell is the basic structural and functional unit of life. All living organisms are made up of cells. Understanding cell structure and functions is essential for building a strong foundation in biology.
Learning Outcomes
After completing this chapter, students will be able to:
- Understand the concept of cell as the basic unit of life.
- Differentiate between unicellular and multicellular organisms.
- Identify major cell organelles and their functions.
- Explain structure and function of plasma membrane and cell wall.
- Understand diffusion and osmosis with real-life examples.
- Differentiate between prokaryotic and eukaryotic cells.
- Compare plant cell and animal cell structure.
Exam Tip: Diagram-based questions of plant and animal cell are very important in exams.
Real Life Applications
Cell biology concepts are directly connected with daily life and living systems:
- Medical Science: Understanding cells helps in studying diseases and treatments.
- Food Preservation: Osmosis is used to preserve food using salt and sugar.
- Water Balance: Osmosis maintains water balance in plant and animal cells.
- Plant Growth: Cell division helps in growth and repair of plants.
- Medicine Delivery: Cell membrane controls entry of drugs into the body.
Important Concept: Mitochondria are called powerhouse of the cell because they produce energy (ATP) required for all activities.
Common Mistakes Students Make
- Confusing cell wall with cell membrane.
- Mixing functions of mitochondria and ribosomes.
- Not understanding difference between diffusion and osmosis.
- Incorrect labeling of cell diagrams in exams.
- Confusing prokaryotic and eukaryotic cells.
- Not remembering functions of Golgi apparatus and lysosomes.
Pro Tip: Always draw neat labeled diagrams of plant and animal cells for better retention and exam scoring.
Conclusion
The chapter “Fundamental Unit of Life” is very important for understanding biology. Strong conceptual clarity about cell structure and organelles helps in higher classes and competitive exams. Regular revision of diagrams and functions will ensure high marks in exams.
Class 9 Science Chapter: Fundamental Unit of Life (Cell)
10 Detailed Solved Examples
Example 1: Identification of Cell Type
A bacterium does not have a nucleus. Identify its type of cell.
Solution:
It is a prokaryotic cell because it lacks a well-defined nucleus and membrane-bound organelles.
A bacterium does not have a nucleus. Identify its type of cell.
Solution:
It is a prokaryotic cell because it lacks a well-defined nucleus and membrane-bound organelles.
Example 2: Diffusion Concept
Why does smell of perfume spread in a room?
Solution:
Due to diffusion, perfume molecules move from high concentration (near source) to low concentration (rest of room).
Why does smell of perfume spread in a room?
Solution:
Due to diffusion, perfume molecules move from high concentration (near source) to low concentration (rest of room).
Example 3: Osmosis Example
A raisin is kept in water. What happens?
Solution:
Water enters raisin through osmosis, causing it to swell.
A raisin is kept in water. What happens?
Solution:
Water enters raisin through osmosis, causing it to swell.
Example 4: Cell Wall Function
Why plant cells do not burst in hypotonic solution?
Solution:
Because of rigid cell wall which prevents bursting.
Why plant cells do not burst in hypotonic solution?
Solution:
Because of rigid cell wall which prevents bursting.
Example 5: Mitochondria Function
Why mitochondria are called powerhouse of cell?
Solution:
They produce ATP (energy) through respiration.
Why mitochondria are called powerhouse of cell?
Solution:
They produce ATP (energy) through respiration.
Example 6: Vacuole Difference
Compare vacuole in plant and animal cells.
Solution:
Plant cell → Large central vacuole
Animal cell → Small or absent vacuole
Compare vacuole in plant and animal cells.
Solution:
Plant cell → Large central vacuole
Animal cell → Small or absent vacuole
Example 7: Cell Theory
State one important point of cell theory.
Solution:
All living organisms are made up of cells.
State one important point of cell theory.
Solution:
All living organisms are made up of cells.
Example 8: Lysosome Function
Why lysosomes are called suicide bags?
Solution:
They contain digestive enzymes that can destroy the entire cell if released.
Why lysosomes are called suicide bags?
Solution:
They contain digestive enzymes that can destroy the entire cell if released.
Example 9: Chloroplast Function
Why plants are green?
Solution:
Due to presence of chlorophyll in chloroplast.
Why plants are green?
Solution:
Due to presence of chlorophyll in chloroplast.
Example 10: Cell Membrane Function
What is the function of plasma membrane?
Solution:
It controls entry and exit of substances and is selectively permeable.
What is the function of plasma membrane?
Solution:
It controls entry and exit of substances and is selectively permeable.
10 Important FAQs
Q1: What is a cell?
A cell is the basic structural and functional unit of life.
A cell is the basic structural and functional unit of life.
Q2: What is difference between plant and animal cell?
Plant cells have cell wall and chloroplast, animal cells do not.
Plant cells have cell wall and chloroplast, animal cells do not.
Q3: What is osmosis?
Movement of water through semi-permeable membrane.
Movement of water through semi-permeable membrane.
Q4: What is diffusion?
Movement of particles from high to low concentration.
Movement of particles from high to low concentration.
Q5: Why nucleus is important?
It controls all activities of the cell.
It controls all activities of the cell.
Q6: What is cytoplasm?
Jelly-like substance where cell organelles are present.
Jelly-like substance where cell organelles are present.
Q7: What is prokaryotic cell?
Cell without a true nucleus (e.g. bacteria).
Cell without a true nucleus (e.g. bacteria).
Q8: What is eukaryotic cell?
Cell with well-defined nucleus.
Cell with well-defined nucleus.
Q9: Why cell membrane is important?
It controls transport of materials in and out of cell.
It controls transport of materials in and out of cell.
Q10: Why study cell is important?
It helps in understanding life processes and diseases.
It helps in understanding life processes and diseases.
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