Robert Hooke discovered cells in 1665 when examining a slice of cork under his microscope. He saw that cork had a honeycomb-like structure consisting of many small compartments, which were later termed cells. All organisms are made of cells, with some being single-celled and others multicellular. Cells have a plasma membrane, nucleus, cytoplasm, and various organelles that allow them to carry out functions necessary for life. The basic components and structures of cells were described.

1. BIOLOGY
HOLIDAY
HOME
WORK
THE FUNDAMENTAL
UNIT OF LIFE

2. HISTORY
 In 1665 Robert Hooke examined the slice of
cork by self designed microscope .
 Cork is a substance which comes from bark of
tree.
 By microscope cork resembled the structure
of a honey comb consisting of many little
compartments.
 This was very important invention in the history
of science that living things appear to consist
of separate small units.
 The word cell use to describe this unit in
biology .

3.  In1839 Purkinje discovered some fluid
substance in the cell termed protoplasm.
 In 1940 with the discovery of electron
microscope complex structure of cell and
various organelles could understand.

4. CELL
 All organisms around us are made up of cells.
 Some organisms are made up of single cell called
unicellular organism .e.g. Amoeba.
 Many cells grouped together in a single body and
perform various functions called multicellular
organisms .
 Some organisms have different kinds of cells with
different shape and size.
 Each living cell has a capacity to perform certain
basic function . That are characteristics of all living
forms .
 All living cell perform this basic function.

5.  As we know there is a division of labour in
multicellular organism such as human being ,
means different part of our body perform different
part of our body perform different functions .
 A single cell also perform different functions with
the help of its component which is known as cell
organelles .
 These organelles together constitute the basic unit
called the cell.

6. STRUCTURE OF A CELL
A cell have 3 features –
 Plasma membrane
 Nucleus
 Cytoplasm
Plasma membrane
Cell membrane is the outer most covering of the cell
that separate the content of the from its external
environment .
Structure
 The plasma membrane is flexible made up of
organic molecules –
Lipid
Protein

7. We can observe the structure of plasma only
through an electron microscope .
 The flexibility of cell membrane also enable the cell
to engulf the food and other material from its
external environment . This process is known as
endocytosis. Ex :- Amoeba enquires its food through
this process.

8. Cell wall
 In plants cells addition to the plasma membrane
another rigid outer covering called the cell wall.
 Structure
 This is made up of complex substance cellulose .
 It provide strength to plant.
Functions
 Cell walls permit the cell of plant , fungi and
bacteria to with stand very dilute external media
without bursting .
 It take water by osmosis.

9. Function of plasma membrane
 Separation of content of cell.
 Permit the entry and exit of material .
 Prevent movement of some other material called
selectively permeable membrane .
 Some substance like carbon dioxide , oxygen can
move across the cell membrane by a process
called diffusion. In diffusion substance move from a
region of high concentration to low concentration.

10. Use of diffusion – waste product can excrete out by
the cell like carbon dioxide , Respiration.
 Movement of water through semi permeable
membrane is called osmosis.
Use of osmosis –
 Transportation of water
 Transportation of dissolve substance
 Transportation of nutritious substance
 Transportation/excretion of waste product
Examples of osmosis – unicellular fresh water organism
and most plant cell absorb water by plant root.

11. Use of diffusion – waste product can excrete out by
the cell like carbon dioxide , Respiration.
 Movement of water through semi permeable
membrane is called osmosis.
Use of osmosis –
 Transportation of water
 Transportation of dissolve substance
 Transportation of nutritious substance
 Transportation/excretion of waste product
Examples of osmosis – unicellular fresh water organism
and most plant cell absorb water by plant root.

12. NUCLEUS
 Nucleus is a darkly coloured spherical or oval
dot like structure near the Centre of each cell.
Structure
 Double layer covering of nucleus – Nuclear
membrane.
 Functions of nuclear membrane – porous and
transfer the material from nucleus to cytoplasm.

13.  Chromosomes are rod shapely structure.
Parts of chromosomes – DNA and protein.
DNA – genes and chromatin .
 Function of Nucleus – cellular reproduction
 Types of nucleus –
 Organisms with poorly defined nuclear membrane
is known as prokaryotes .
 Organisms with well defined nuclear membrane is
known as eukaryotes.

14. NUCLEUS
Nucleus
chromosome
DNA
Genes Chromatin
Protein
Nuclear
Membrane

15. CYTOPLASM
 The cytoplasm is the fluid content inside the plasma
membrane. It contains many specialized cell
organelles .
CELL ORGNELLES
 Large and complex cells of multicellular organism
need a lot of chemical activities to support their
complicated structure and functions.
 To perform these activities membrane bounded
little structures are present called organelles, this is
the feature of eukaryotic cell
 These organelles are visible only with electron
microscope.

16. TYPES OF CELL
PROKARYOTIC CELL
Size:generally small
Nuclear region :poorly
defined, nuclear membrane is
absent.
Chromosome : single
Membrane-bounded cell
organelles absent .
EUKARYOTIC CELL
Size:generally large
Nuclear region :well defined ,
nuclear membrane is present.
Chromosomes : more than
one.
Membrane-bounded cell
organelles present.

17.  These organelles are :
1. Endoplasmic reticulum
2. Golgi apparatus
3. Lysosomes
4. Mitochondria
5. Plastids
6. Vacuoles
ENDOPLASMIC RETICULUM (ER)
 It is a large network of membrane bound tubes and
sheets.

18. Structure
 Long tubules and round or oval vesicles.
Type
 Rough Endoplasmic Reticulum (RER)
 Looking rough under microscope because it contains
particles called ribosomes attached to its surface.
Ribosomes : sight of protein manufacturer
depending on need.
 Smooth Endoplasmic Reticulum (SER)
Size of SER –
 Varies in size
 Smooth in different cells and forms network system.

19. Functions Of Endoplasmic Reticulum
 Transport of material like protein within the cell
organs .
 Providing a surface framework for some
biochemical activities of cell.
 Detoxifying many poison and drugs .
GOLGI APPARATUS
 It was discovered by Camilo Golgi by his name is
called Golgi Apparatus .

20. Structure
 Membrane bounded vesicles arrange
approximately parallel to each other called cistern.
 It is also connected with the membrane of ER so its
also complex cellular membrane system.
Functions
 Storage
 Modifications
 Packaging of products in vesicles
 Formation of lysosomes

21. LYSOSOMES
 It is known as waste disposal system of the cell .
 Helps to keep the cell clean by digesting any
foreign material like bacteria or food.
 It contains powerful digestive enzymes which help
to digest foreign materials .
 It is also known as suicide bags of a cell.
Structure
 Membrane bound sacs, filled with objective
enzymes.

22. MITOCHONDRIA
 Mitochondria are known as power house of the
cell.
 It release energy for various chemical activities.
Structure
 It have 2 membrane covering outer membrane
is very porous while inner one is deeply folded .
 These folds create a large surface area for
formation of ATP.

23. Functions
 ATP is Adenosine triphosphate .
 It produce energy so it is known as the energy
currency of the cell.
 It is a organelle of sense because it produce DNA
PLASTIDS
 Plastids are present only in plant cells.
Types
 Chromoplast – coloured plastids–green , yellow etc.
 Leucoplast – white or colourless plastids .

24. Structure
 The internal organization of the plastids consist of
numerous membrane layers embedded in a
material called the stroma.
Functions
 It contains pigment chlorophyll known as
chromoplast and leucoplast .
 Chloroplast contain pigment chlorophyll used for
photosynthesis , it is found in the chromoplast.
 Leucoplast is used for storage.
 Plastids work like mitochondria because its own
DNA and Ribosomes

25. VACUOLES
 Vacuoles are storage sac for solid or liquid
contents.
 In plant cells there is very large central
vacuole , providing rigidity to cell.

26. CONCLUSION
 Cells have a basic structural organization with the
help of membrane and organelles.
 Cells perform functions like respiration, obtaining
nutrition, forming new proteins and cleaning of
waste materials etc.
 Thus cell is the fundamental structural and
functional unit of life.

27.  PRESENTED BY –
 Paridhi Gouri Patel
 CLASS – 9th