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1. CLASS - 9
BIOLOGY
CHAPTER 1
THE FUNDAMENTAL UNIT OF LIFE

2. Introduction

3. Robert Hooke Discovery
❖ While examining a thin slice of cork, Robert
hooke see that structure resemble the
structure of a honeycomb consisting of many
little compartment.
❖ Cork is a substance which comes from the
bark of a tree.
❖ This was in year 1665 the Robert hooke
made this chance observation through a self
designed microscope Robert hooke called
these boxes cell's.
❖ Cell is a Latin word for “a little room.”
❖ But Hooke Discovery is not much successful
because he discovered the dead cell's.
Robert Hooke Microscope

4. Leeuwenhoek Discovery of Cell
❖ In 1674 Leeuwenhoek discovered the free
living cell in pond water with improved
microscope.
❖ He also discovered the many cells such as
sperm cell, WBCs, etc.
Leeuwenhoek’s Microscope

5. Robert Brown Discovery of Nucleus
❖ Robert Brown was a Scottish botanist and
paleobotanist that discovered the nucleus
in 1831.
❖ Robert Brown named the nucleus and it
has stick till now.
❖ Robert Brown made other discoveries
such as the identification of the naked
ovule of the gymnospermae plants.
❖ Robert Brown discovered the nucleus
while he was studying the epidermis of the
orchids under the microscope.
Robert Brown Microscope

6. Purkinje naming for Cell
❖ Purkinje in 1839 coined the term
“Protoplasm” for the fluid substance of
Cell.
❖ He also proposed many theory's for cell.

7. Cell Theory
Theodor Schwann Matthias Jakob Schleiden
1839 1838

8. Schledien and Schwann Theory about Cells
❏ Theodor Schwann 1839 & Matthias Jakob Schleiden 1838 proposed the cell
theory which is following:-
1. All living organisms are composed of one or more cells
2. The cell is the most basic unit of life Schleiden's theory of free cell formation
through crystallization was refuted in the 1850s by Robert Remak, Rudolf
Virchow, and Albert Kolliker.[7] In 1855, Rudolf Virchow added the third tenet
to cell theory. In Latin, this tenet states Omnis cellula e cellula.[10] This
translated to:
3. All cells arise only from pre-existing cells.

9. R. Virchow
In 1855 he suggested that all
cells arise from pre existing
cells.

10. In 1940, it is possible to observe and
understand the complex structure of cell
and it's various parts and organelles.

11. Difference between Unicellular & Multicellular
UNICELLULAR
➢ Uni means single, i.e. unicellular means
single cell organisms.
➢ For Example -
❏ Amoeba
❏ Paramecium
❏ Chlamydomonas
❏ Bacteria, etc.
MULTICELLULAR
➢ Multi means many, i.e. Multicellular means
many cell organisms.
➢ For Example -
❏ Plantae Kingdom
❏ Animal Kingdom
❏ Fungi, etc.

12. Some organisms can also have cells of
different kinds.The shapes and sizes of
cells are related to the specific functions
they perform. As Amoeba have changing
shape but Nerve cell have a typical
shape.

13. Various cells from the human body
Fig. 5.3 NCERT

14. What is Cell made up of? What is the structural
organisation of a cell
❏ As we know that cell has a special components called organelles. And
it well maintain the whole system inside the cell.
❏ A cell is made up of following part's :-
1. Plasma Membrane
2. Nucleus
3. Cytoplasm
❏ All activities inside the cell and interactions of cell with its environment
are possible due to this features.

15. Plasma Membrane
❏ This is the outermost covering of the cell
that separates the contents of the cell from
its external environment.
❏ The Plasma Membrane allows or permits
the entry and exit of some materials in and
out of the cell.
❏ It also prevent movement of some
materials. Therefore, is called a
Selectively Permeable Membrane.
❏ In 1972 Singer and Nicholson proposed
Fluid Mosaic Model of Plasma Membrane.
The following image shows the Plasma
Membrane :-

16. Diffusion & Osmosis
Diffusion
❏ The spontaneous movement of a
substance from a region of high
concentration to a region where it's
concentration is low.
❏ Similar to this it happens in cells when
concentration of Carbon di oxide is high
inside as compared to outside
environment of cell then carbon di oxide
moves from inside of cell to outside of cell.
❏ It takes place in all states of Matter.
Osmosis
❏ Water also obeys law of diffusion.
❏ The movement of water molecules through
such a Selectively Permeable Membrane
is called Osmosis.
❏ The movement of water across the
Plasma Membrane is also affected by
amount of substance dissolve in it.
❏ It takes place in only water state

17. Hypotonic
Solution
If the medium surrounding the
cell has a higher water
concentration than the cell,
meaning that the outside
solution is very dilute, the cell
will gain water by osmosis. Here
the cell likely to be swell up.
Hypo - Less

18. Isotonic
Solution
If the medium has exactly the
same water concentration as the
cell, there will be no movement
of water across the cell
membrane. In this cell will be in
same sizes.
Iso - Equal

19. Hypertonic
Solution
If the medium has a lower
concentration of water than the
cell, meaning that it is a very
concentrated solution, the cell
will loose water by osmosis.
In this cell will shrink.
Hyper - More

20. ★ The Plasma Membrane is flexible and is
made up of organic molecules called
lipids and proteins.
★ The flexibility of cell membrane also
enables the cell to engulf in food and
other materials from its external
environment. Such process is known as
Endocytosis.

21. Cell Wall
❏ It is a rigid outer covering.
❏ It lies outside the Plasma Membrane
❏ Plant cell Wall is mainly composed of
cellulose.
❏ Cellulose is a complex substance and
provide structural strength to plants.
★ When a living plant cell looses water
through osmosis there is shrinkage or
contraction of contents away from the cell
wall. This phenomenon is called
Plasmolysis.
★ Cell wall permits the cells of plants, fungi,
and bacteria to withstand very dilute
external media without bursting.

22. Nucleus
❏ The Nucleus is double layered substance.
❏ Its covering is known as Nuclear Membrane.
❏ The Nucleus contains the chromosomes,
which are visible as rod - shaped structures
only when the cell is about to divide.
❏ Chromosome contains information for
inheritance of features from parents to next
generation in form of DNA(Deoxyribo
Nucleic Acid) molecules.
❏ Chromosome contains DNA and Protein.
❏ Functional segment are called gene.
❏ Chromatin materials is visible as entangled
mass of thread like structure.
❏ Whenever the cell is about to divide, the
chromatin materials gets organised into
chromosome.

23. Difference between Prokaryotic and Eukaryotic Cell
Prokaryotic Cell
❏ Size : Generally small (1- 10 micrometer)
❏ Nuclear region : Not well defined and not
surrounded by Nuclear Membrane and
known as Nucleoid.
❏ Chromosome : Single
❏ Membrane bound cell organelles are
absent.
Eukaryotic Cell
❏ Size : Generally large (5-10 micrometer).
❏ Nuclear region : Well defined and
surrounded by a nuclear membrane.
❏ More than 1 chromosome.
❏ Membrane bound cell organelles are
present.
The significance of the membrane can be understood by virus as viruses lack Membrane and hence
do not show characteristic of life until they entered a living body and use it's cell machinery to multiply.

24. Types of cell

25. Cell Organelles

26. Endoplasmic Reticulum (ER)
❏ It is a large network of membrane bound tubes and
sheets.
❏ It is of two types :-
★ Rough Endoplasmic Reticulum :- It is so because it
has a particles Ribosomes attached to it's surface.
And helps in protein synthesis.
★ Smooth Endoplasmic Reticulum :- It help in
manufacture of fat molecules, or lipids, important for
cell function.
★ Some of these proteins and lipids help in building the
cell membrane. This process is known as membrane
biogenesis.
★ One function of ER is to serve as channels for the
transport of materials (especially proteins) between
various region of cytoplasm or between the
cytoplasm and the Nucleus.

27. Do you know
❏ ER also functions as a cytoplasmic
framework providing a surface for some
of the biochemical activities of the cell.
❏ SER plays a very important role in
detoxifying many poisons and drungs in
liver of many vertebrae.

28. Golgi Apparatus
❏ The Golgi Apparatus, first described by
Camilo Golgi, consisting of system of
membrane bound vesicles arranged
approximately parallel to each other in
stacks and cisterns.
❏ The materials synthesised near the ER is
packaged and dispatched to various
targets inside and outside the cell through
the Golgi Apparatus.
❏ It's function includes the storage,
modification, and packaging of many
products in vesicles.
❏ The Golgi Apparatus is also involved in the
formation of lysosome.

29. Lysosome
❏ Lysosome are kind of waste disposal
system of cell.
❏ Lysosome helps to keep the cell clean by
digesting any foreign material as well as
worn out cell organelles.
❏ Lysosomes are able to do thisbecause
they contain powerful digestive enzymes
capable of breaking down all organic
materials.
❏ Sometimes lysosome may burst and
enzymes digest their own cell, therefore
lysosomes are also known as “suicide
bags of cell.”
❏ Lysosome are single membrane bound
cell filled with digestive enzymes, these
enzymes are made by RER.

30. Mitochondria
❏ Mitochondria is also known as
“Powerhouse of the cell.”
❏ Mitochondria release energy in the form of
ATP (Adenosine triphosphate) molecules.
❏ ATP is known as currency if the cell.
❏ Mitochondria is double layered bound
organelle.
❏ Mitochondria have there own DNA and
Ribosomes.
❏ Mitochondria are able to make their own
Proteins.

31. Plastids
❏ It is present only in plant cell.
❏ There are mainly 3 types of plastids :-
1. Chromoplast (Coloured Plastids)
2. Leucoplast (Non colour)
3. Chloroplast (Green colour Plastids)
❏ Chloroplast are important for
photosynthesis.
❏ Leucoplast are important for storage of
starch, oils, and proteins granules.
❏ Plastids also contains their own DNA and
Ribosomes.

32. Vacuoles
❏ Vacuoles are storage sacs for solid or
liquid contents.
❏ Vacuoles are small in animals cell while
large in plant cell.
❏ The central vacuoles of some plants cell
may occupy 50-90% of cell volume.
❏ In plant cell vacuoles provide turgidity and
rigidity to the cell.
❏ Vacuoles play important role in transfering
the materials.

33. Thank you