1. The document provides an introduction to cell biology, discussing key topics such as the cell theory, different types of cells in the human body, microscopy techniques used to study cells, and the historical development of cell biology as a field of study. 2. Important milestones discussed include the invention of the microscope in the 16th century, Hooke and van Leeuwenhoek's early observations of cells in the 1660s-1670s, the formulation of the cell theory in the 1830s-1840s, and later discoveries like the nucleus, chromosomes, and organelles that advanced understanding of cellular structure and function. 3. The cell theory states that all living things are made of cells, cells are

1. Cell Biology
an introduction...
By
Dr. Jeevan Jyoti Kaushik,
Asst. Professor.
ACHS

2. Motivation: why cell biology

3. CELLS
• the most basic unit of life
• can become organism by themselves.
• can function as part of a larger organism
• have different unique structure and
function

4. I. Why Study Cells?
A. Body is made up of cells:
1. RBC
2. Nerve Cells
3. Skin Cells
4. Muscle Cells
5. White Blood Cells
6. T Cells & B Cells
7. Reproductive Cells

5. B. Certain Cells can make us sick
• Bacterial Cells
• Cancer Cells
• Protists

6. Harmful Micro-organisms
• Disease causing (pathogens)
– bacterial disease : e.g.
cholera, sore throat,
tuberculosis
– fungal disease : e.g. athlete’s
foot , ringworm
– protozoa disease : e.g.
malaria, sleeping sickness
athlete's foot
Dust Mite - multicellular

7. 7
Infectious diseases
Nearly 2,000 different
microbes cause diseases.
10 B new infections/year
worldwide
13 M deaths from
infections/year worldwide

8. 8
C) Cells at Work
Agriculture - used to control crop insects.
Bioremediation - a field of environmental biotechnology
where bacteria are used to clean up toxic wastes.eg-Oil spills.
Pharmacology - developing anti-microbials drug (antibiotics
and other chemotherapeutic substances) to destroy
pathogens.
Vaccines - developing weakened strains of pathogenic
bacteria or viruses in order to protect (immunize) against
infection.
Food production: bread, bear, cheese yoghurt.

9. •How to study cell ?
•The Study of Cell
Structure: Microscopy and
Specimen Preparation
•Techniques for cell
fractionation

10. Light Microscope

11. TRANSMISSION ELECTRON MICROSCOPE (TEM)
• uses electrons
• Thin slices of specimen.
• Study internal organization.

12. TEM Image of Plant Cell

13. •A beam of electrons
move across a specimen
and constructs an image
showing details of its
surface.
•Produces 3D images
•Specimen surface metal
coated.
•surface topographical
study of mainly biological
specimens.
SCANNING ELECTRON MICROSCOPE (SEM)

14. SEM IMAGES
Bee eyeball Edge of mosquito
wing
Hairs on a fly

15. Techniques for cell
fractionation

16. 2005-2006
Isolating organelles
• Cell fractionation
–separate organelles from cell
–variable density of organelles
• ultracentrifuge

17. 2005-2006
Ultracentrifuge
• spins up to 130,000 rpm

18. 2005-2006
Microcentrifuge
• Biotechnology research
–study cells at protein &
genetic level

19. Why is the understanding of cell mechanics
important?
• cells need to move and interact with
their environment
• cells have components that are highly
dependent on mechanics, e.g.,
structural proteins.
• cells need to reproduce / divide to
improve the control/function of cells to
improve cell growth/cell production
• mechanical signals regulate cell
metabolism , E.g. treatment of certain
diseases needs understanding of cell
mechanics. Insulin

20. 20
Human Lung Cell
Virus
Proteins on cell
surface
H attaches to cell surface
proteins so virus can enter
cell
Virus genes are released into the
cell.
The lung cell is ‘tricked’ into
using these genes to make new
virus particles.
N cuts the links between the viruses
and the cell surface so virus particles
are free to go and infect more cells.

21. • Cell morphology to understand how
mechanically gated ion channels work an
understanding of the loading in cells could aid
in developing structures to grow cells or
organization of cells more efficiently.
• understand how cells is affected by and affects
its environment .
• Understand how mechanical factors alter cell
behavior (gene expression) .
• how does cell mechanics change provide
guidance for cell manipulation.

22. Helps to study ……….
• How do cells maintain their shape?
What are the mechanical properties of the individual
components that give the cell it’s strength and elasticity?
What are their stability limits?
• How do cells move?
What are the structural components that support cellular
motion?
• How do cells transport material?
What are the mechanisms by which proteins are
transported from their production site to their working
site?
• How do cells interact with their environment?
What are the cell’s mechanisms to sense environmental
changes and respond to them?

23. • Cell biologists focus on the microscopic features of
the living world.
• In this discipline, molecules are important subjects
for study along with cellular structures that are,
themselves, made up of highly organized assemblies
of molecules.
• The study of cell by microscopy, known as
cytology, has been joined with biochemical,
physiological and genetic studies to produce the
discipline of cell biology.
• This merger of ideas and methods from different
spheres of biological study has led us to examine
cells as dynamic living units.

24. Definition
• The cell biology or Cytology (Gr., Kytos =
hollow vessel or cell, logous = knowledge) is a
biological science, which deals with the study
of cells from morphological, biochemical,
physiological, genetical and developmental
point of views.
It is biological science that has taken its
individual entity by the end of the
nineteenth century.

25. Cell biology and other biological sciences
• The cell biology has helped the biologists to
understand various complicated life activities such
as-
• Metabolism
• Growth
• Differentiation
• Heredity
• Evolution at the cellular and molecular level
Due to its wide application in various branches of
biological science, many new hybrid biological
sciences, have sprung up.
Some of them are as follows :

26. Genes, RNAs, proteins, metabolites, and ions
(Genetics, molecular biology, biochemistry,
physiology)
Cellular/subcellular processes
(Cell Biology)
Growth Development Responses to
Environment

27. 1. Cytotaxonomy (cytology and taxonomy)
• Each plant and animal species has a
definite number of chromosomes in its
cells and the chromosomes of the
individuals of a species resemble closely
with one another in shape and size.
• These characteristics of chromosomes
help a taxonomists in determining the
taxonomical position of a species.

28. • Further, cell biology furnishes strong
support to the manner of origin of
certain taxonomic units. Therefore,
the cytotaxonomy can be defined as
“ a cytological science which provides
cytological support to the taxonomic
position of any species”.

29. 2. Cytogenetic (Cytology and genetics)
• Cytogenetic is that branch of cell biology
which is concerned with the cytological
and molecular bases of heredity,
variation, mutation, phylogeny,
morphogenesis and evolution of
organisms.

30. 3. Cell physiology (cytology and physiology)
• The cell physiology is the study of life
activities, viz., nutrition, metabolism,
growth, reproduction or cell division
and differention of the cell.
• It has helped in understanding various
complicated physiological activities at
cellular level.

31. 4. Cytochemistry (cytology and Biochemistry)
• The cytochemistry is that branch of
cytology which deals with the chemical
analysis of living matter
• For example, the cytochemical analysis has
revealed the presence of carbohydrates,
lipids, proteins, nucleic acid and other
organic and inorganic chemical compounds
in the cells.

32. 5. Cytopathology
• The application of cytology to pathological
science has helped in understanding
various human disease at cellular and
molecular level.
• Because many diseases that are caused due
to disorder of genetic codes in DNA
molecule which alter the synthetic process
of enzymes and ultimately disturbs
metabolic activities of the cell.

33. 6. Cytoecology (cytology and ecology)
• The cytoecology is the science in which one
studies the effects of ecological changes in
the cell.
• The cytoecological studies on plants and
animals have revealed that the ecological
habitat and geographical distribution have
the correlation with cellular aspects of
living organism.

34. 7. Molecular cytology
• A branch that helps to understand the biological
phenomena in molecular terms.
• Knowledge of ultra structure of the cell is of
fundamental importance because practically all the
functional and physico chemical transformations take
place with the molecular architecture of the cell and
at molecular level.
• The discoveries in molecular biology such as the
discovery of molecular model of DNA by Watson and
Crick (in 1953), molecular interpretation of protein
synthesis mechanism, genetic code etc., have an
extraordinary impact on modern cell biology and
biology.

35. • Thus , the cell biology has given a great
impetus to early and modern biologists to
explore new vistas in biological sciences.
• The modern cytological studies are helpful
in understanding various life activities in
the terms of molecules, in the curing of
various chronic human disease and in
improving the breeds of plants and
animals.

36. BRIEF HISTORICAL BACKGROUND
Update on cell biology…………

37. •Historical landmarks produced the modern
approach to study the biology of cell as an
integrated and co-ordinated living system
•Microscopy and the cell concept
•If cell and their components are to be studied,
artificial aids are needed to magnify them.
• The study of cell biology has been
inseparable from the development of the
microscope. The beginning of the cell study
must therefore be traced to the invention of
the microscopes that allowed the scientists to
see cells.

38. History - Janssen
• The invention of the first useful
compound microscope is
credited to Zacharias Jansen
and Hans Janssen, of
Middleburg, Holland (1590-95).
This microscope could magnify
an object 30 times is actual
size.
• Janssen and his father made a
compound microscope by
placing two convex lenses at
each end of a tube
• The simple microscope was
invented by Gallileo (1610)

39. Robert Hooke (1665)
• Credit for the first
significant information
gained by using
microscopy goes to
Robert Hooke (1665)
• Coined the term cell.
• The word “cell” is derived
from the Latin word
'cellula' which means
small compartment.

40. Robert Hooke (1665)
• He published his
observation in
“Micrographia “.
• discovered cells in a piece
of cork.
• The cells that Hooke
observed were dead cells.
• the 1st cytologist

41. • Nehemiah Grew added his
observation in publications (1672-82)
• Two volumes of information and
illustrations on “microscopic plant
anatomy”.
• Laid the foundations for cell
concepts

42. Anton Van Leeuwenhoek (1673)
Anton van Leeuwenhoek was
the first to observe and
describe magnified living
things with simple
microscope.
magnification 200 times.
 Leeuwenhoek was the first
to see bacteria from teeth
scrapings and animal-like
protist from pond water.
1st to drew the images.
He sent letters to Royal
society in London.
Father of microbiology.

43. • Little new information about cellular
structure appeared until the 1830s.

44. • Improved microscope
• Microtome was invented in 1870,
allowed controlled sectioning of
tissues and thin slices became readily
available for microscopical studies.
• In addition to new and improved
instruments, newly manufactured
stains and dyes made it possible to
obtain high contrast among cells and
cell structures.

45. • These technical advances, it led to
improve the cell and tissue studies and
ultimately led to the development of the
modern concept of the cell. These major
developments took place between 1830
and early 1900s in a continuing
progression.
• The first major step was the recognition of
the nucleus. Improved microscopic lenses
made it possible.

46. Robert Brown
• Around 1831, Robert
Brown reported the
discovery of the nucleus.
• In the course of his
microscopic studies of the
epidermis of orchids,
discovered in these cells
"an opaque spot," which
he named the nucleus.
• Publication of report in
1833 to emphasize the cell
nucleus

47. History of Cell Theory
• It was the German professor
of botany at the University of
Jena, Dr. M. J. Schleiden who
proposed all plants are
composed of cells.
• The following year,
Dr.Theodor Schwann (1839)
who worked with animals,
stated that all animals are
made of cells

48. • published a book on animal
and plant cells. summarized
observations into three
conclusions about cells:
1) The cell is the unit of
structure, physiology, and
organization in living things.
2) The cell retains a dual existence
as a distinct entity and a
building block in the
construction of organisms.
3) Cells form by free-cell
formation, similar to the
formation of crystals.

49. • Cell theory: The postulate the cell in an underline unit
of structures of all organisms was formulized in the cell
theory by T. Schwann and M. Schleiden (1838-39)
• The cell theory enjoyed immense success and was at
once adopted by zoologist and botanists. One reason
for delay in understanding the role of the nucleus at
this time was the influence of Schwann’s ideas on
many biologist. He had proposed that daughter cells
formed within the mother cells. Because this idea was
accepted by others, attention by diverted away from
the nucleus and its contribution to the new cell
generations.
• 1840: J. Purkinje coined the term protoplasm to refer
the fluid contents of cells.

50. History of Cell Theory - Virchow
• We know today that the first two
tenets are correct, but the third is
clearly wrong.
• The correct interpretation of cell
formation by division was finally
enunciated in Rudolph Virchow's
powerful 1859 proclamation,
"Omnis cellula e cellula"... "All
cells only arise from pre-existing
cells“
• Rudolph Virchow proposed that
cells can only arise from
previously existing cells.

51. The Cell Theory
The modern tenets of the Cell Theory include:
1.All known living things are made up of cells.
2.The cell is structural & functional unit of all
living things.
3.All cells come from pre-existing cells by
division.
– Cells contains hereditary information which is passed
from cell to cell during cell division.
– All cells are basically the same in chemical composition.
– All energy flow (metabolism & biochemistry) of life
occurs within cells.
The Cell Theory is to Biology as Atomic Theory is to
Physics.

52. 53
ENDOSYMBIOTIC THEORY
• In 1970, American biologist, Lynn
Margulis, provided evidence that
some organelles within cells were
at one time free living cells
themselves
• Supporting evidence included
organelles with their own DNA
• Chloroplast and Mitochondria
copyright cmassengale

53. 54
copyright cmassengale

54. • 1865- Gregor J. Mendel
discovered the basic
rule/principles of heredity.
• He 1st conducted well designed
breeding experiments.
• He concluded “heritable
factors” (genes) retained
individuality generation after
generation.
• These factors governed the
development of 7 characteristics
he studied in pea plant.
• Mendel’s work was not
recognized until 20th

55. • 1869- Johann Friedrich Miescher
discovered a new substance, which he
called nuclein.
• A white substance from the nucleus of
human cells and fish sperms.
• He found proportion of N & P was
different from any other known
constituent of cells.
• The importance of the nucleus to cell
continuity was firmly established in
1870’s.

56. • 1879: Walter Flemming
coined the term Mitosis (in
which he observed splitting of
chromosomes and distributed
to two daughter cells.)
• He also coined the term
chromatin for the stainable
material of the nucleus.
• 1882: E. Strasburger
discovered the cell division in
plant cell.
• Coined the term cytoplasm
and nucleoplasm.

57. • 1881: Edward Zacharias showed chromatins
are composed of nuclein.
• 1889: Richard Altmann renamed nuclein to
nucleic acid.
• 1888: W. Waldeyer coined the term
chromosome.
• 1885: A. F. W. Schimper used the term
‘Plastid’ derived from the greek word
“Plastikas” (moulded).

58. • 1885: Rabl demonstrated that chromosome
remained physically intact between generation.
• 1891: Camilo Golgi recognized golgi complex
in the nerve cells of owl and cat.
• Kolliker: observed mitochondria for 1st time in
1880.
• He teased them from muscle cells of insect.
• He noted granules possess a membrane that
swelled in water.
• Flemming in 1882 named them mitochondria
as fila.

59. • Later on Altmann made systematic observation
on them and named them bioblast.
• The present name mitochondria was
assigned by Benda in 1898.
• Hogbomm(1948) showed that mitochondria is
the site for cellular respiration.
• Nass (1963) actually observed and proved the
presence of DNA in mitochondria.
• 1945: E.R was 1st reported by Porter.
• 1953: the ribosomes were 1st noted in plant
cells by Robinson and Brown (in bean roots) .
• Palade isolated ribosomes from animal cells
and detected the RNA in them 1956.

60. 20th century began…
• The 20th began with the momentous
rediscovery of G. Mendel’s studies of
inheritance in garden peas.
• By 1900 Hugo De Vries and Carl Correns
independently cited Mendel’s experiments in
their report of inheritance studies.
• 1902 : W.S. Sutton and T. Boveri put forward
“the chromosomes theory of inheritance”
proposing chromosomes to be the vehicles of
heredity information.

61. • 1905: Farmar and Moore coined the
meiosis.
• 1909: Johansson coined the term gene
for mendelian factors.
• 1911: Thomus Hunt Morgan discovered
genes on chromosomes are discrete
units of heredity.
Model: Drosophila melanogaster.
The rules of mendelian inheritance were
rapidly extended and accepted.

62. • The relationships
between chemical
activities involving
organic compound and
living organism had
been clearly
demonstrated earlier by
Louis Pasteur who
showed that
fermentation of sugar
to alcohol would
proceed only if certain
microorganisms were
also present.
Louis Pasteur

63. 64
Robert Koch (1882)
• Used aniline dyes to stain
microorganisms.
• Identified cause of
anthrax (Bacillus
anthracis), Tuberculosis
(Mycobacteria
tuberculosis), and
cholera (Vibrio cholerae)
• Developed pure culture
methods.
Insert figure 1.12

64. • There was very little exchange between
chemists and biologists before 1940s
and 1950s.
• By 1900 chemical structures of all 20
amino acids had been identified by
different biochemists.
• 1902: Emil fischer showed amino acids
are linked and form proteins.
• Proteins properties are defined by amino
acid composition and arrangement.

65. • Buchner accidently discovered that sugars
could be fermented in cell free extracts of yeast
and this led to systematic study and description
of enzymes.
• 1926: J.B. Sumner: First enzyme to be
crystallized – Urease.
• 1920: Levene (biochemist) determined basic
structure of nucleic acids:- composed of P, N-
base, Pentose sugar
• 1928: Frederick Griffith gave the
phenomenon of transformation. The agent for
transforming streptococcus went undiscovered
until 1940s.

66. • Biologists were not very interested in
DNA, It was thought to have a simple
sequence like synthetic polymer.
• 1941: Beadle and Tatum identify that
genes make proteins.
• 1944: Avery, Mc Carty and Macleod found
transforming substance was DNA.
• 1950: Edwin Chargaff : Cytosine
complements guanine and Adenine
complements Thymine

67. • 1952: Alfred Hershey and Martha Chase showed
DNA as genetic material {Bacteriophages}.
• 1953: James D. Watson and Francis Crick
proposed molecular model of DNA- was widely
accepted.
• Combined studies of gene behavior led to the new
discipline of cytogenetics, which blended
information from cytology and genetics into a
coherent and cross supporting body of evidence.
• 1960s: The advent of molecular cytogenetics.
• This discipline forms a substantial portion of
modern cell biology.

68. Measurement of Cell
Size

69. 70
Cell Size
Question:
Are the cells in an elephant bigger,
smaller, or about the same size as
those in a mouse?

70. • A small cell has a greater ratio of surface
area to volume than a large cell of the
same shape
30 µm 10 µm
Factors Affecting Cell Size

71. 2005-2006
What limits cell size?
• Surface to volume ratio
–as cell gets bigger its volume increases faster
than its surface area
• smaller objects have greater
ratio of surface area to volume
Why is a huge
single-cell
creature not
possible? 6:1 ~1:1 6:1
s:v

72. Limits to cell size
• Metabolic requirements
–in large cell, cannot move material in & out
of cell fast enough to support life
CHO
CHO
aa
aa
CH
CO2
NH3
O2
aa
aa
O2
CHO
aa
CH
O2
aa
CHO
CH
aa
O2
CO2
NH3
NH3
CO2
CO2
NH3
CH O2

73. 74
Cell Size
Cell size is limited.
-As cell size increases, it takes longer for
material to diffuse from the cell membrane to
the interior of the cell.
• If cell size is large then the surface area is
no longer great enough to get rid of all the
wastes and to get in enough food and
water.
• Therefore, the cells of an organism are small
in size

74. 75
Cell Size
Question:
Are the cells in an elephant bigger,
smaller, or about the same size as
those in a mouse?
About the same size,
but…
The elephant has MANY
MORE cells than a mouse!

75. Units of measurements of Cell
• The cells of most animals, plants and
bacteria have microscopic size and these
are measured by the fractions or multiples
of standard units.
• The standard units are; meters, Kilograms
and seconds.
• The meter is the standard unit of
measurement of length.
• The standard unit of mass is the
international Kilogram.
• The standard unit of time is Second

76. • A number of fractions or multiples of
meters are commonly used in
measurement of length of cell and its
components.
• One thousandth of a milimetre (10-6 m)
is called a micron and is given the
symbol μ.
• One thousandth of a micron (10-9 m) is
the milimicron (m μ)/ nanometer (n).
• The gram (10-3 Kg) is the most
commonly used unit of mass in cell
biology.

77. 78
How Big is a Micron ( µ ) ?
1 cm = 10,000 microns
copyright cmassengale

78. Limits to cell size
• Lower limit
–smallest bacteria, mycoplasmas
• 0.1 to 1.0 micron (µm = micrometer)
–most bacteria
• 1-10 microns
• Upper limit
–eukaryotic cells
• 10-100 microns

79. Thanks
for your kind attention