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๐ฌ Think about it
Look at a brick wall. It is made of thousands of small bricks stacked together. Living things are built the same way — from tiny blocks too small to see. What are these blocks, and what is inside them? Let's find out.
What is a cell?
Cell
Small empty space
what Hooke saw in a thin slice of cork
Basic unit of life
the smallest building block of every living body
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A cell is the basic unit of life; every living body is made of one or more cells.
- All living beings are made up of cells.
- A cell is the smallest building block of life.
- Cells are usually too small to see without a microscope.
What are the basic parts of a cell?
Which parts make up every cell?
The cell
Basic unit of life
Cell membrane
The outer layer
Porous, lets material pass
Example:
Onion peel cell membrane
Cheek cell membrane
Cytoplasm
Jelly-like material inside
Life processes happen here
Example:
Carbohydrates
Proteins
Fats
Mineral salts
Nucleus
Round, in the middle
Controls the whole cell
Example:
Regulates all activities
Regulates growth
| Part | What it is |
|---|---|
| Cell membrane | The outer layer of the cell |
| Cytoplasm | The jelly-like material inside |
| Nucleus | The round structure in the middle |
| Cell wall (plant) | An extra strong outer layer |
| Chloroplast (plant) | A green plastid that contains chlorophyll |
| Vacuole (plant) | A large, fluid-filled space |
- Every cell has three basic parts.
- Plant cells also have some extra parts, shown below.
What do these parts of the cell do?
| Part | Its job |
|---|---|
| Cell membrane | Encloses the cell and controls what enters and leaves |
| Cytoplasm | Holds the cell's materials; most life processes happen here |
| Nucleus | Controls all the cell's activities and its growth |
| Cell wall | Gives the plant cell strength and rigidity |
| Chloroplast | Traps sunlight to make food (photosynthesis) |
| Vacuole | Stores substances, removes waste, and keeps the cell firm |
- Each part has its own special job.
- Together they keep the cell alive and working.
Are cells the same in plants and animals?
What does a plant cell have extra?
Plant and animal cells
Same basics, some extras
Plant cell
Has more parts
Cell wall gives rigidity
Plastids and a big vacuole
Example:
Onion peel cell
Animal cell
Has fewer parts
No cell wall, no plastids
Vacuole small or absent
Example:
Cheek cell
- No, they are not exactly the same.
- Both have a membrane, cytoplasm, and nucleus.
- But plant cells have some extra parts.
How is a plant cell different from an animal cell?
Plant Cell
Animal Cell
Has a strong outer
cell wall
.
Has
no cell wall
.
Has green
chloroplasts
to make food.
Has
no chloroplasts
.
Has a
large vacuole
.
Has a small or no vacuole.
- A plant cell has an extra outer cell wall for strength.
- It has green chloroplasts that help make food.
- It has a large vacuole that stores substances and keeps shape.
๐ฌ
Activity 2.2 — Let us study a cell (Teacher demonstration activity)
How do we prepare an onion peel slide?
Wash an onion and cut it
Cut the bulb vertically into pieces
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Pull out the thin inner peel
Use forceps to lift the transparent layer
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Stain it with safranin
30 seconds in the red stain, then rinse in water
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Mount it in glycerin
Lower a coverslip at 45°, then blot the extra glycerin
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Under the microscope: nearly rectangular cells, packed with no space — like bricks in a wall
In this Activity, we will prepare an onion peel slide and look at plant cells under a microscope.
Materials needed
An onion, a blade, safranin stain, glycerin, a glass slide, a coverslip, a needle, and a microscope.
Procedure
1. Take an onion and break it into pieces.
2. Peel a thin, transparent layer from the inner side of a piece.
3. Place this peel flat on a clean glass slide.
4. Put one or two drops of safranin stain on it.
5. Add a drop of glycerin over the peel.
6. Gently lower a coverslip with a needle, avoiding air bubbles.
7. Place the slide under the microscope and focus.
2. Peel a thin, transparent layer from the inner side of a piece.
3. Place this peel flat on a clean glass slide.
4. Put one or two drops of safranin stain on it.
5. Add a drop of glycerin over the peel.
6. Gently lower a coverslip with a needle, avoiding air bubbles.
7. Place the slide under the microscope and focus.
Observation
You see nearly rectangular cells packed closely together, like bricks in a wall.
Explanation
The onion peel is made of many cells, which shows that all plants are made of cells.
Onion peel cells are nearly rectangular and packed with no space between them — like bricks in a wall.
โ Summary
- Onion peel shows packed cells
- Cells look like bricks in a wall
- Confirms plants are made of cells
๐ฌ
Activity 2.3 — Let us investigate
How do we prepare a cheek cell slide?
Rinse your mouth with clean water
Then scrape the inner cheek with a blunt toothpick
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Spread the scraping on a slide
In a drop of water, spread evenly
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Add a drop of methylene blue
The blue stain increases the contrast
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Add glycerin and a coverslip
After a minute; blot off the excess
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Under the microscope: polygon-shaped cheek cells — a membrane, cytoplasm and nucleus, but no cell wall
In this Activity, we will prepare a slide of our own cheek cells and compare them with onion peel cells.
Materials needed
A clean spoon or ice-cream stick, methylene blue stain, glycerin, a glass slide, a coverslip, and a microscope.
Procedure
1. Rinse your mouth well with clean water.
2. Gently scrape the inside of your cheek with the flat side of a clean spoon.
3. Spread the scraping on a clean glass slide.
4. Add a drop of methylene blue stain.
5. Add a drop of glycerin and place a coverslip over it.
6. Observe the slide under the microscope.
2. Gently scrape the inside of your cheek with the flat side of a clean spoon.
3. Spread the scraping on a clean glass slide.
4. Add a drop of methylene blue stain.
5. Add a drop of glycerin and place a coverslip over it.
6. Observe the slide under the microscope.
Observation
You see polygon-shaped cells that form the lining of the mouth. They have a membrane, cytoplasm, and nucleus, but no cell wall.
Explanation
Animal cells like cheek cells have the basic parts but lack a cell wall, unlike plant cells.
Cheek cells are polygon-shaped and have no cell wall — only a membrane, cytoplasm and nucleus.
โ Summary
- Cheek cells are an animal cell example
- They have membrane, cytoplasm, nucleus
- They have no cell wall
Important Points
- Cell membrane, cytoplasm, and nucleus are the basic parts of every cell.
- The cell wall (in plants, fungi, bacteria) gives extra strength and rigidity.
- Plant cells have chloroplasts and large vacuoles; animal cells usually do not.
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Test Yourself
-
What is the smallest unit of life?
View Answer
The cell. -
Name the three basic parts of a cell.
View Answer
Cell membrane, cytoplasm, and nucleus. -
Which part controls the cell's activities?
View Answer
The nucleus. -
Which extra layer do plant cells have?
View Answer
The cell wall. -
What gives a plant cell its green colour?
View Answer
Chloroplasts, which contain chlorophyll.
Important Definitions
- Cell — The basic building block of all living things.
- Cell membrane — The outer layer that encloses the cell and controls what enters and leaves.
- Cytoplasm — The jelly-like material inside the cell where most life processes happen.
- Nucleus — The round central part that controls the cell's activities and growth.
- Cell wall — An extra strong outer layer found in plant, fungal, and bacterial cells.
๐ A step further
- Plant cells have tiny rod-shaped structures called plastids .
- Some plastids, like chloroplasts , hold chlorophyll — this makes them green and helps in photosynthesis.
- In the non-green parts of a plant, plastids store substances instead.
- Plant cells also have a large, empty-looking space called a vacuole , which stores substances, removes waste, and keeps the cell’s shape.
- In animal cells vacuoles are usually absent; if present, they are small.
- So a cell is not a simple bag of liquid — it is a complex structure whose many parts each do a special job.
