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The Cell and Its Parts
- All living beings are made up of cells.
- A cell has three basic parts.
- The outer lining is the cell membrane.
- The round structure in the middle is the nucleus.
- The space between them is filled with cytoplasm.
Example 1 — Onion Peel Cell
- Onion peel cells look like neat rectangles.
- They are packed closely, like bricks in a wall.
- They also have an extra outer cell wall.
Example 2 — Cheek Cell
- Human cheek cells look polygon-shaped.
- They have a membrane, cytoplasm, and nucleus.
- But they have no cell wall.
Important Points
- The cell membrane is porous and lets materials in and out.
- Most life processes happen in the cytoplasm.
- The nucleus controls all the cell's activities and growth.
- The cell wall gives plant cells strength and firmness.
Definition — Cell
A cell is the basic unit of life that makes up the body of every living being.
Definition — Cell Membrane
The cell membrane is the porous outer lining that encloses the cell and controls what enters and leaves it.
Definition — Nucleus
The nucleus is the round structure that regulates all the activities and growth of the cell.
Definition — Cell Wall
The cell wall is an extra outer layer in plant cells that gives them rigidity and strength.
Materials needed
An onion bulb and forceps.
Safranin stain and glycerin.
A glass slide, coverslip, and microscope or foldscope.
Safranin stain and glycerin.
A glass slide, coverslip, and microscope or foldscope.
Procedure
Peel a thin transparent layer from an onion piece.
Stain it with safranin, then rinse in water.
Place it on a slide and add a drop of glycerin.
Lower a coverslip without trapping air bubbles.
View it under the microscope.
Stain it with safranin, then rinse in water.
Place it on a slide and add a drop of glycerin.
Lower a coverslip without trapping air bubbles.
View it under the microscope.
Observation
You see nearly rectangular cells, packed closely together with no gaps.
Explanation
These are onion peel cells. They look like bricks in a wall, showing plants are made of cells.
◆ Summary
- Peel and stain onion skin.
- Mount and view it.
- See rectangular cells.
- Packed like bricks.
Materials needed
A clean toothpick.
Methylene blue stain and glycerin.
A glass slide, coverslip, and microscope.
Methylene blue stain and glycerin.
A glass slide, coverslip, and microscope.
Procedure
Rinse your mouth and gently scrape the inside of your cheek.
Spread the material in a drop of water on a slide.
Add methylene blue, then glycerin.
Cover with a coverslip and view it.
Spread the material in a drop of water on a slide.
Add methylene blue, then glycerin.
Cover with a coverslip and view it.
Observation
You see polygon-shaped cheek cells, which line the inside of the mouth.
Explanation
These cells have a membrane, cytoplasm, and nucleus, but no cell wall. So animal cells differ from plant cells.
◆ Summary
- Scrape cheek cells.
- Stain blue and view.
- See polygon cells.
- No cell wall in them.
⭐ A Step Further — Plastids and Vacuoles
Plant cells have tiny structures called plastids. Green ones, called chloroplasts, contain chlorophyll and help in photosynthesis.
Plant cells also have a large vacuole that stores substances and keeps the cell's shape. Animal cells have only small vacuoles, or none. So a cell is a complex structure with many parts, each with its own job.
