INTRODUCTION TO CELLS INTRODUCTION TO CELL THEORY HISTORY FORMULATION OF CELL THEORY CLASSICAL CELL THEORY DRAWBACKS OF CLASSICAL THEORY MORDEN CELL THEORY EXCEPTION OF CELL THEORY SIGNIFICANCE OF CELL THEORY HOW HAS THE CELL THEORY BEEN USED CONCLUSION

1. THE CELL THEORY
By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. SYNOPSIS
 INTRODUCTION TO CELLS
 INTRODUCTION TO CELL THEORY
 HISTORY
 FORMULATION OF CELL THEORY
 CLASSICAL CELL THEORY
 DRAWBACKS OF CLASSICAL THEORY
 MORDEN CELL THEORY
 EXCEPTION OF CELL THEORY
 SIGNIFICANCE OF CELL THEORY
 HOW HAS THE CELL THEORY BEEN USED
 CONCLUSION

3. INTRODUCTION TO CELL
The cell is the fundamental structural and
functional unit of all living organisms.
All the activities of an organism are present
in miniature form in each and every cell.
Robert Hooke (1665) is credited with the
discovery of cell.
Cell retain the dual existence as a distinct
entity (unicellular organism) and a building
block in the construction of multicellular
organism.
There are two types of cell- prokaryotic and
eukaryotic cell

4. 2 Basic Cell Types
Prokaryotes Eukaryotes

5. INTRODUCTION TO CELL THEORY
 The cell theory or cell doctrine, states that all
organisms are composed of similar units of
organization called cells.
 The concept was formally articulated in 1839
by M.Schleiden and T.Schwann and has
remained as foundation of modern biology.
 Cell theory also provides us with an operational
definition of life.
 Cell theory is to biology is as atomic theory in physics.

6. HISTORY OF CELL THEORY
384-322 B.C.- ARISTOTLE concluded that
“all animals and plants consist of certain repeated
structures’’
1485- DA VINCI recommended the uses of
lenses in viewing small objects.
1595- JANSSEN invented the first useful
compound microscope having magnification up
to 10x & 30x. These microscope were called
“flea glasses”.

7. 1658- JAN SWAMMERDAN gave the first
description of the cell in his account of the RBC
of the frog.
1661- MARCELLO MALPIGHI was the first to
use microscope to examine and describe the thin
slices of animal tissues from such organs as the
brain, liver, kidney, spleen, lungs etc. He
distinguish animal and plant cell. He states that
plant and animal tissue were composed of
structural unit which he termed “utriculi” and
“sacculi”.

8. Discovery of Cells
 1665- English Scientist, ROBERT HOOKE, discovered cells
while looking at a thin slice of cork.
 He described the cells as tiny boxes or a honeycomb
 He thought that cells only existed in plants and fungi
 In1665 he published a collection under the title “Micrographia”

9. Anton van Leuwenhoek
 1673- Used a handmade microscope to observe
pond scum & discovered single-celled organisms
 He called them “animalcules”
 He also observed blood cells from fish, birds,
frogs, dogs, and humans
 Therefore, it was known that cells are found in
animals as well as plants

10. 150-200 Year Gap???
 Between the Hooke/Leuwenhoek discoveries and the
mid 19th century, very little cell advancements were
made.
 This is probably due to the widely accepted,
traditional belief in Spontaneous Generation.
 Spontaneous generation states that the microbes arises
automatically in decomposing organic matters
 Examples:
-Mice from dirty clothes/corn husks
-Maggots from rotting meat

11. PASTEUR’S EXPERIMENT
 He showed that boiled medium could remain clear in a
“swan necked” flask open to the air through a sinuous
horizontal tube in which dust particles would settle as
air reentered the cooling vessel.
 When neck was broken it allow entry of bacteria and
microbial growth appear.

12. FORMULATION OF CELL THEORY
 1838- German Botanist, MATTHIAS SCHLEIDEN
brought nucleus to popular attention & asserted it’s
importance in function of cell.
 He believe that nucleus is original structure from which
the remainder of cell is developed.
 He called it cytoblast
 He outlined his view in epochal paper
published in Muller’s Archives in
1938 under the title “Beitrag zur
phytogenesis”

13. FORMULATION OF CELL THEORY
 1839- German physiologist, THEODAR
SCHWANNN, who was a close friend of Schleiden,
noted a strange resemblance of embryonic cord
material (from which the spinal column develop) to
vegetable cells.
Due to schleiden work on nucleus he
reasoned that there is similarity
between both cells and nucleus must
be present in animal tissue.
Through closer study he found
“opaque spots” in abundance

14. spots are found at regular interval it mean
in different compartment of animal tissue
In 1839 SCHWANN published a book
Main theme of book is
-unifying plant and animal tissue
-accepting cell structure as the basis of all
plant and animal tissue

15.  1846- K.NAGELI showed that plant cell arise from
the division of preexisting cells
 1858- RUDOLF VIRCHOW, German physician,
after extensive study of cellular pathology,
concluded that cells must arise from preexisting
cells.
FORMULATION OF CELL THEORY

16. CLASSICAL CELL THEORY
The 3 Basic Components of the Cell Theory
were now complete:
1. All organisms are composed of one or more
cells. (Schleiden & Schwann - 1838-39)
2. The cell is the basic unit of life in all living
things. (Schleiden & Schwann - 1838-39)
3. All cells are produced by the division of
preexisting cells. (Virchow - 1858)

17. Classical cell theory doesn’t gave any
particular knowledge about cell organelles and
their functions.
Also can’t explain the various metabolic
processes of the cell.
The hypothesis was made by observing few
cells and hence was not applicable to all.
It hadn’t explain about the genetic material of
the cell and their transmission to the next
generation
DRAWBACK OF CLASSICAL CELL
THEORY

18. DISCOVERIES LEADING TO MODERN
CELL THEORY
1869- MIESCHER isolated DNA
1879- FLEMMING described chromosome
behaviour during mitosis
1939- COMMERCIAL TRANSMISSION
ELECTRON MICROSCOPE
1953 –WATSON AND CRICK proposed DNA
double helix structure
1965- SCANING ELECTRON MICROSCOPE
2000- HUMAN GENOME SEQUENCE DRAFT

19. MORDERN CELL THEORY
Modern Cell Theory contains 5
statements, in addition to the original
Cell Theory:
The cell contains hereditary information
(DNA,RNA) which is passed on from cell to
cell during cell division.
All cells are basically the same in chemical
composition and metabolic activities.

20. All basic chemical & physiological
functions are carried out inside the cells
(movement, digestion, etc)
Cell activity depends on the activities of
sub-cellular structures within the cell
organelles, nucleus, plasma membrane)
All energy flow (metabolism &
biochemistry) of life occurs within cells.

21. EXCEPTION OF CELL THEORY
Cell theory does not have universal application i.e.
there are certain living organisms which do not have
true cell.
According to cell theory a true cell share the
following three basic characteristics:
 a set of genes
 a limiting plasma membrane
 a metabolic machinery
Various living beings which not easily fit in these
parameters of a true cell e.g. viruses, Rhizopus,
vaucheria, paramecium etc.

22. Viruses
 Viruses are made up of two chemical protein and
nucleic acid, but have no membrane, nucleus,
protoplasm.
 Viruses also lacks metabolic machinery for
energy production and for protein synthesis.
 They appear to be alive
when they reproduce
after infecting a host cell.
T2 phage virus

23. Rhizopus, Vaucheria &
Paramecium
 These organisms also not fit in to the purview of
the cell theory.
 All of these organisms have bodies containing
undivided mass of protoplasm which lacks cell
organization and has more then one nucleus.
Vaucheria
Paramecium

24. Mitochondria & Chloroplast
Theses cell organelles have their own genetic
material and reproduce independently from
the rest of the cell.
Mitochondria Chloroplast

25. According to endosymbiotic theory primitive
host cell, which carried out anaerobic
respiration by glycolysis, were invaded by
bacteria like parasites which respired
aerobically.
Later these host cell is better adapted to it’s
increasingly aerobic environment.
Endosymbiotic aerobic bacterium eventually
would develop as mitochondria

26. Similarly , symbiotic association with
cynobacteria could lead to the formation of
chloroplast and photosynthetic eucaryotes
Mitochondria and chloroplast resembles to
bacteria in size, shape , genes for r-RNA&
t-RNA.
Both of them contain DNA material in
closed circle like that of bacteria.

27. Human RBC
 Human RBC is also a exception of cell theory
because it doesn’t have nucleus.
 Due to lack of nucleus the life span of RBC is
very short.

28. SIGNIFICANE OF CELL THEORY
It make us able to classify between animate
and inanimate objects.
It helps us to link living and non living.
Also helpful to make us understand the
nature of primordial cell and it’s evolution.
Cell theory is a unifying paradigm which
will explain all the biological phenomenon.

29. HOW HAS THE CELL THEORY BEEN USED
The basic discovered truths about cells, listed in
the Cell Theory, are the basis for things such as:
– Disease/Health/Medical Research and Cures(AIDS,
Cancer, vaccine)
– Infield of plant biotechnology
– In stem cell research
– In embryology

30. Some Parting Thoughts
 It is amazing to think that the cells that make up
our bodies are just as alive as we are. Humans are
just an intricately designed community of cells,
which must work together to survive.
 Cells, in my opinion, are one of the strongest cases
for intelligent design by our Creator God!

32. REFERENCES
BOOK &
JOURNALS
EDITION AUTHOR
Cell and Molecular
biology
2005 Gearld Karp
Cell Biology 2006 C.B.Powar
Microbiology 2005 L.M.Prescott
Journal 1 1990 P.Mazzerolo
Journal 2 1988 Charles Malery
 Website- www.ias.ac.in
www.bio.miami.edu.
www.lexic .uscell theory
www.springerlink.in