The Bio Brief

 Observation of Different Cells

We can prepare temporary mounts of:

• Leaf peel
• Onion peel (different sizes)
• Tip of onion root

After observing them under a microscope, we can answer some important questions.

(a) Do all cells look alike in shape and size?

 No Cells differ in shape and size.

(b) Do all cells look alike in structure?

 Yes (basically)

• Most cells have similar basic structures.
• They contain common parts like cell membrane, cytoplasm, and nucleus.

(c) Are there differences among cells from different parts of a plant?

 Yes

• Cells from leaf, root, and stem are different.
• They perform different functions.

(d) What similarities do cells have?

• All cells:
  • Are living units
  • Perform basic life functions
  • Have similar cell organelles

Cell Shape & Function

• The shape and size of a cell depend on the function it performs.
• Some cells have fixed shapes, while others change shape.

 Examples:

• Amoeba → changing shape (helps in movement and feeding)
• Nerve cell → long and branched (helps in transmitting messages)
• Red blood cells → round and flexible (helps in carrying oxygen)

 Flow Chart: Shape Depends on Function

Different Functions

        ↓

Different Cell Shapes

        ↓

Better Performance of Work

 Cells in the Human Body

• Human body has many different types of cells.
• Each type of cell has a specific role.

Examples:

• Muscle cells → movement
• Nerve cells → carry messages
• Blood cells → transport substances

 Division of Labour

 In Multicellular Organisms

• Different organs perform different functions.
  • Heart → pumps blood
  • Stomach → digests food

 Inside a Cell

• Division of labour also exists within a cell.
• Each cell contains cell organelles.
• Each organelle performs a specific function.

Cell Organelles & Their Functions

Organelle	Function
Nucleus	Controls the cell
Mitochondria	Produces energy
Ribosomes	Make proteins
Vacuole	Stores materials
Lysosomes	Clean waste
Chloroplast (plants)	Makes food

 Flow Chart: Division of Labour in Cell

Cell

 ↓

Cell Organelles

 ↓

Each Organelle Has a Function

 ↓

Cell Works Properly

 Important Point to Remember

• All cells have similar organelles, no matter:
  • what organism they belong to
  • what function they perform

 Because of these organelles, a cell can live and carry out all life activities.