Definition :- Cell is the structural and function unit of living organism.

Discovery of cell

Robert Hooke :- He discovered the cell from thin “cork”slice and name as cellula. this is published in him book “micrograpghia”.

Robert Brown :- He discovered the nucleus the “nucleus” from “orchid root.”

Dujardin :- He discovered protoplasm.

Purkinje :- He coin the term Protoplasm.

R.virchow :- Given the “omnis cellula’ e’ cellula, mean new cell ariese always from pre existing cell.

Huxley :- He called “protoplasm is the physical basis of life”.

Cell Theory

It was formulated by two biologist “m.j.schleiden (1838),and “T. Schwann”(1839).

According to them ‘the cells the structural and functional unit of all living beings’.

But the cell theory expanded by ‘VIRCHOW’, cell theory state that.

1. bodies of the living beings are made up of cells. the cell is the unit of life

2. Activities of an organism are the sum total activities of its cell.

3. Every new cell arises from pre existing cell..

Exception of cell theory



Aim-to Demonstrate Plant Cell


Put the peel of onion in water to prevent drying and folding.

Spread the peel uniformly on the slide.

Excess of stain should be removed.

There should be no air bubble in the slide.

Size and Shape of the Cell

Size Of The Cell

Normal size of human cell is 20 micrometre to 30 micrometre.

1. Largest Cell :- in animals-ostrich egg(15cm)

    In plants-Acetabularia(6-10cm)

2. Longest Cell :- In animals-nerve cell(abt.1m).

    In plants-hemp fibre

3. Smallest Cell :- PPLO (Pleuro Pneumonia like organism.

Shape of Cell Depends on Function’s

1. Elongated and branched :- Nerve Cell.

2. Spindle shape :- Muscle Cell.

3. Branched :- Pigment cell of skin and bone cell.

4. cuboidal :- Germ cell of gonads.

5. Discoidal :- RBC.

6. Spherical :- Egg.

7. Slipper shaped :- Paramecium.

8. Polygonal :- Liver Cell.

9. Irregular :- Amoeba.

Unicellular and Multicellular Organism


Made up of single cell.

Single cell perform all functions.

Division of labour is absent.

Example :- Bacteria, Amoeba, Pa-ramecium, Chlamydomonas.


Made up of large no of cell.

Cell specify to perform different function.

Division of labour is present.

Fungi(except-yeast), all Plants, Animals.

Structure of cell

The basic cell structure mainly composed of three components,

Plasma membrane

Cytoplasm- it is again divided into two parts

1. Cytosol

2. Cell organelles

a. Non membranous-ribosome n centrosome.

b. Single membranous-Golgi body ,ER ,lysosome etc.

c. Double membranous-plastid n mitochondria.

Nucleus – It is composed of four part

Nuclear membrane



Chromatin threads.

Plasma membrane, Cell membrane ,plasma lemma

Definition – it is living, flexible, semipermeable ,selectively permeable membrane that enclose the contents of cell.

Function of plasma membrane.

It allow nutrients and other essential elements to enter the cell.

It allow waste material to remove the cell.

Flexibility make able to engulf in food and other material(endocytosis).


The process of taking in a bulk of materials from external environment into the cell.

Type :- 

Pinocytosis :- Taking of liquid materials.

Phagocytosis :- Taking of solid.

Transport across plasma membrane

Type-2 type

1. Passive transportation:- when the substances moves from its high concentration to lower concentration(according to concentration gradient) without use of energy.

2. Active transportation:- when the substances moves from its lower concentration to higher concentration(against to concentration gradient) with use of energy

Type of passive transportation




The process of movements of substances from the region of its higher concentration to lower concentrations as to spread uniformly in the given space.

Example:- metabolic gases (co2 n o2 move into and out the cell through the diffusion.


Definition :- Diffusion of water or solvent from its higher concentration to its lower concentration across semi permeable membrane.

Example :- Absorption of water by plants roots.

Absorption of water by unicellular organism.

Type of Osmosis

1. Exosmosis :- when a cell is placed in hyper tonic solution ,than water will come out from the cell ,this is called exosmosis.

2. Endosmosis :- when a cell placed in hypotonic solution water will enter into the cell, this is called endosmosis.

PLASMOLYSIS :- when a fully turgid cell changed into the flaccid cell ,that process is called plasmolysis.

Type of solution

In comparison to concentration of cell, there are three type of solution

Hypertonic solution :-  when the concentration of solution is more than the cell.

Hypotonic solution :- when the concentration of solution is less in comparison to cell.

Isotonic solution :- when the solution have same concentration as cell.

Demonstration of endosmosis and exosmosis

Put dry resins in petri dish having plain  water.

Observe after 30 minutes.

Raisins swells due to endosmosis.

Some swollen raisin placed into salt solutions.

After 15-30 min raisin will shrink due to the exosmosis.

Type of Solutions

In comparison to concentration of cell, there are three type of solution.

Hypertonic solution :- When the concentration of solution is more than the cell.

Hypotonic solution :- When the concentration of solution is less in comparison to cell.

Isotonic solution :- When the solution have same concentration as cell.

Cell wall

Definition :- It is outermost, rigid, freely permeable ,protective covering found outside the plasma membrane in all plants, bacteria, BGA, and all fungi.

Composition :-

In plants-cellulose

In fungi-chitin/fungal cellulose.

In bacteria and BGA-peptidoglycan.

Function :-

1. It provide a definite shape to the cell.

2. Provide protection and support to cell.

3. It prevent undue expansion of the cell in hypotonic solution.

Demonstration of Plasmolysis


Other Name :- Brain of cell, head quarter of cell, controller of cell.

Discovery :- Robert brown by orchid root.

Definition :- nucleus is double membrane bound dense protoplasmic body, which controls all cellular metabolism and encloses the genetic information of cell.


it have following four components :- 

Prepare temporary slide of human cheek cell