The document provides an overview of cell biology, detailing the discovery of cells, the development of cell theory, and the structure and function of various cellular components such as prokaryotic and eukaryotic cells, membranes, organelles, and organelle functions. It covers significant historical milestones in microscopy, cytoplasmic organelles like mitochondria, Golgi complex, and lysosomes, and discusses the differences between plant and animal cells. Additionally, it highlights cell fractionation, the cytoskeleton, and the significance of various organelles and their contributions to cellular function.

2. By Sajjad Hussain Mirani
Sindh University Jamshoro

3. What Is Cell?
 Cell is the smallest entity in which life can
exist.

5. How Cell Was
Discovered? Cells are microscopic in nature so
their discovery was dependent upon
the invention of microscope.
 Microscope was invented by David
Jensen in 1590 A. D. But 1st
useful
microscope was invented by Galileo (a
great astronomer) in 1610 A.D.

7. Galileo

8.  In 1665 A.D. Robert Hooke discovered cell
by his own made microscope in a slice of
cork.

9. What Hooke Had Seen?
 Robert Hooke seen many small empty
spaces which he named as cell (empty
room)

12. Who Discovered The Nucleus?
 In 1831 A.D. Robert Brown discovered the
nucleus in the cells of orchid.

13. Who Discovered Cytoplasm?
 In 1839 A.D. Schwann observed that
nucleus was surrounded by a fluid in cell.
Now named as cytoplasm.

15. Introduction To Cell Theory
 Put forward by Schleiden (a botanist) and
Schwann (a zoologist) in 1839 A.D.
 Cell theory was later corrected by Rudolf
Virchow in 1855 A.D.

16.  Schwann.
 Schleiden.
 Virchow.

17. Points Of Cell
Theory1. Cell is a basic unit of life.
2. All living organisms are made up of
cells.
3. New cells are produced from
preexisting cells.

18. Definition Of Cell
Now cell is defined as “Structural and
functional unit of life made up of
protoplasm containing nucleus
surrounded by cytoplasm and bounded
by cell membrane.

21. What Is Microscope?
 Microscope is an optical instrument through
which we can visualize small objects which
we are unable to see with naked eye.
 In 1590 A.D. David Jansen invented 1st
microscope.
 Later Galileo, Robert Hooke and other
scientists made useful developments in
microscope.

22. Types Of
Microscope On the basis of source of illumination microscope is
divided into following three types.
1. Light Microscope
Type of microscope in which light is used as a
source of illumination.
2. X – Ray Microscope
Type of microscope in which x – rays are used as a
source of illumination.

24. 3. Electron Microscope
 Most powerful microscope.
 Can magnify objects up to 10,000 times.
 Built in 1930’s.
 Electron beam is used as source of
illumination.

26. Qualities Of Microscope
 A science student should three qualities of a
microscope.
1. Magnification
Magnification is measurement of ability of
microscope to enlarge images.
Magnification can be calculated by multiplying power
of eyepiece with the power of objective lenses.
2. Resolution
It is measurement of clarity of image.

28. Qualities Of Microscope
3. Contrast
Ability of microscope to distinguish b/w two closely
related points or features in a microscopic field.

30. Isolation Of Cellular Components
Cell fractionation is a technique to isolate various parts of cell to
determine their composition.
In cell fractionation 1st
number of cells are open in an ice cold
environment.
Then cells are placed in homogenizer or motor to break various
parts of cell.
In last cells centrifuged by the spinning action of centrifugation
machine.
Large particles e.g. nucleus, etc are settle on slow while small
particles e.g. ribosome are settled on fast motion.

33. Types Of Cells
Cells are basically of two types
Prokayotic Cell
 It is a type of cell which lack all membrane
bounded cellular structures.
Eukaryotic Cell
 It is a type of cell which contain all
membrane bounded structures.

35. Prokayotic Cell & Eukaryotic Cell
Do not contain membrane
bounded nucleus.
Nuclear material is
concentrated in a region
called “Nucleoid”.
Do not contain other
membrane bounded structures.
Only contain mesosomes which
are infoldings of cell
membrane for the respiration
purpose.
Prokaryotes are unicellular
living organism like
bacteria, etc.
Contain a membrane bounded
nucleus in their cells.
Nucleus is very well defined
and usually spherical in
shape.
Contains all membrane
bounded cell organelles.
Contain mitochondria, Golgi
bodies, endoplasmic
reticulum, lysosome,
peroxisome, etc.
Eukaryotes are both multi
cellular and unicellular in
nature.

39. Parts Of Eukaryotic
Cell A eukaryotic cell usually contain following
four parts.
1. Plasma Membrane.
2. Cell Wall.
3. Cytoplasm.
4. Nucleus.

41. Plasma Membrane
 Also called cell membrane, plasma lemma.
 Outer boundary of animal cell and second outer
most boundary of plant, bacterial and fungal
cells.
 Protects cytoplasm.
 Helps in transport of different materials across
it.
 It is semi permeable in nature

42. Composition
 Cell membrane is made up of following
substances.
1. Lipids (phospholipids and cholesterol).
2. Proteins (intrinsic and extrinsic).
3. Carbohydrates.

43. Lipids
 They are arranges in 2 parallel layers called lipid bi layer.
 Have two ends i.e. polar and non polar ends.
 The non-polar ends faces each other.
 Polar heads are linked with Carbohydrates and Proteins
 Phospholipids most important lipid molecule.
 Cholesterol is also present.

44. Lipid Bi Layer Of Cell Membrane

45. Structure

46. Fluid Mosaic Model
 Most popular model which explains the structure of
cell membrane.
 Given by Singer & Nicolson (1972).
 According to this model lipids are forming bi layer.
 Proteins are either completely inside or outside.
 Protein molecules act like channels which transport
different substances from place to place.

47. Proteins
Integral or Intrinsic Proteins
They are located inside phospholipid bi
layer of cell membrane.
Peripheral or Extrinsic Protein
They are located outside the
phospholipid bi layer of cell
membrane.

48. Proteins Of Cell Membrane

49. Functions
Cell membrane performs various functions few
important are as follows,
Diffusion (both passive and facilitated).
Osmosis.
Active transport.
Endocytosis.
Exocytosis.

51. Cell Wall
 Outer most boundary of plant, bacterial and algal
cells.
 Made up of cellulose which are non living
carbohydrate molecules.
 Made from Cellulose and pectin.
 Some times lignin may be present.
 Cell wall may have three parts (Middle lamella,
Primary cell wall and Secondary cell wall)

52. Middle Lamella
 It is a layer between 2 daughter cells is
called middle lamella.
 When it dissolves, the daughter cells
separate.
 Composed of calcium and magnesium
pactate.

53. Primary Wall
 Formed inside the middle lamella.
 1st
layer which is synthesized by cell.
 It is thin in young cells.
 In mature cells it becomes thick.
 It is made of 50% hemi cellulose, 25%
cellulose and some pectin

54. Secondary Wall
 It is formed inside the primary
wall.
 It is made from cellulose
 Some times Lignin is also added in
it

55. What is Plasmodesmata?
 These are the places of cell wall where
deposition of wall material does not take
place.
 Plasmodesmata are pores in cell wall.

57. Functions Of Cell Wall
 Provide mechanical support to the cell.
 Give specific shape to the cell.
 Provide cell with the property of rigidity.
 Hydrophilic so helps in imbibition of
water.

59. Facts About Nucleus
 Discovered by Robert Brown in 1831.
 Nucleus all activities of cell.
 Usually spherical in shape.
 Bounded by perforated nuclear membrane.
 There may be one, two or more nuclei per
cell.

60. Components Of Nucleus
 Nucleus contain following parts.
 Nuclear membrane.
 Nucleoplasm or Karyolymph.
 Chromatin network.
 Chromosomes.
 Nucleic Acids.

61. Diagram Of
Nucueus

62. Nuclear membrane
 Out boundary of nucleus
 It has pores called nucleo-pores
 Nuclear pores allows different substances
to pass from nucleus to cytoplasm.
Nucleoplasm
 It is a fluid which is filled inside the
nucleus.
 It is also known as karyolymph.

63. Chromatin Network
 It is a term which refer to the uncoil
chromosomes which are present inside
the nucleus.
 These sort of chromosomes are seen
during interphase
Chromosomes
 Chromatin network coils upon itself to
form a thread like structure called
chromosomes.
 Chromosomes are species specific i.e.
every species have an specific number
of chromosomes like 46 in man.

65. What Is Cytoplasm
 Cytoplasm is a part of protoplasm
which lies b/w cell membrane and
nuclear membrane.
 Cytoplasm is collection of many small
sub units called cytoplasmic
organalles.
 Cytoplasmic organalle are of following
types.

66. Endoplasmic Reticulum (ER)

67. Important Facts About ER
 Intracellular network of tubules which
act like pathway for transporting
materials.
 ER extend from cell membrane to
nuclear membrane.
 Of Two types, i.e.

68. Rough ER Smooth ER
 Highly coated with
ribosome.
 Occur in protein
synthesizing cells.
 Found in pancreas,
slivery glands, etc.
 Surface is not
coated with
ribosome.
 Occur chiefly in
steroid producing
cells.
 Found in adipose
tissue, etc.

69. Functions Of ER
 In skin it converts cholesterol into vitamin D.
 Rough ER gives platform to ribosomes.
 ER provides pathway for import/export.
 Help in protein synthesis.
 Help in detoxification.
 Smooth ER involves in lipid synthesis.

70. Mitochondria

71. Key Facts Of
Mitochondria Present in all eukaryotic cells so it is a universal structure.
 Also known as chondriosomes.
 Rod shape, cigar shaped, capsule shape, etc.
 Remain in constant motion.
 They are center of respiration of cell.
 0.2-1.0u in diameter and 10u in length.

72. Internal Structure
 Double membrane bounded structure.
 Outer membrane is smooth.
 Inner membrane is folded and folds are known as Cristae.
 Folds are filled with matrix.
 Cristae has enzymes and co-enzymes required for oxidation of
pyruvate.
 Here, glucose, amino acids and fatty acids are digested and
ATP are made.
 They are called Power Houses of cell.

73. Unique Characters Of
Mitochondria
 They have their own DNA.
 They are semi-autonomous.
 Can produce new mitochondria
independent of cell division.
 Transfer only by mother to her
offspring.

74. Golgi Complex

75. Important Points About Golgi
 Discovered by Camilo Golgi (1898).
 Also called Dictyosomes in plants and invertebrates.
 They have Cisternae.
 One in animal cell.
 Many in plant cells.
 Located near to the nucleus.

76. Functions Of Golgi
Bodies Act as packaging centre in cell where different
proteins are packed and transported to various parts
of cell.
 They store proteins.
 Make enzymes & Co-enzymes.
 In plants, they make cell wall.
 In animals they make lysosomes

77. Lysosomes

78. Important Points About Lysosomes
 Lysosomes are formed by Golgi bodies.
 They contain various types of digestive enzymes so
help in intra cellular digestion.
 Lysosomes are found in animal cells.
 They can lead to digestion of their own cell if their
membrane got ruptured so also known as suicidal
sacs.
 The process in which lysosomes digest their own
cell is called autophagy of cell.

79. Lysosomal Storage
Diseases Lysosomes have alpha – glycosidase enzyme.
 Absence of alpha glucosidase leads to
glycogen storage in lysosomes.
 Due to extra glycogen, lysosomes are
ruptured.
 Ruptured lysosomes releases enzymes which
digest cells.

80. Lysosomal Storage
Diseases Tay – Sachs.
 Gaucher’s Disease.
 Krabbe’s Disease.

81. Plastids

82. Key Points Of Plastids
Double membrane bounded organelles.
Occur in greatest number in plant cells.
Plastids are absent in animal cells.
Immature and colorless plastids are found in newly
formed cells of meristem and are known as
proplastids.
Plastids are of three types i.e.

83. 1. Chloroplast
 Contain chlorophyll.
 Give green color to plant.
 Manufacture food by photosynthesis.
 Contain its own DNA and
2. Chromoplast
 Contain pigments like xanthophylls, carotenes, etc.
 Give various color combination in plants except
green.

84. 3. Leucoplast
 Colorless plastids.
 Developed in absence of sunlight.
 Commonly found in all under ground parts
of plant.

85. Peroxisomes

86. Key Facts About Peroxisomes
 Single membrane bounded structures.
 Contain enzymes for transferring hydrogen atom
to oxygen.
 Forms hydrogen peroxide (H2O2).
 Hydrogen peroxide is broken down by catalase.
 Thought to metabolize alcohol so abundant in
alcohol metabolizing cells.

87. Glyoxisomes
 Single membrane bounded structures.
 Found in plants only.
 Present in fat storing tissues.
 Contain fine granular stroma.
 Having enzymes that convert fats into
carbohydrates i.e. gluconeogenesis.

88. Cytoskeleton

89. Facts About Cytoskeleton
 These are straight fibers made up of proteins.
 They are located in cytoplasm and support the
structure of cell.
 Help in cell division.
 Help in locomotion in form of cilia, flagella, etc.
 Maintain shape of cell.
 There are 2 types microtubules and microfilament

90. Microtubules
Microfilament
 Hollow
 25nm diameter
 Made of tubulin
protein
 Solid
 7nm diameter
 Made of Actin
protein

91. Intermediate
Filament 8-11nm in size.
 Rope like.
 They are made of keratin protein.
 They make skin and hairs.
 They give support only.

92. Ribosomes

93. Key Facts About
RibosomesNamed because contain high concentration of
RNA.
One of the most vital cell organelles.
Ribosome are chief site for protein synthesis
so also known as protein factories of cell.
Manufactured in nucleolus.
Found free as well as attached to surface of
rough endoplasmic reticulum.

94. Contain about 50 types of different proteins.
There is millions of ribosome present per cell.
Each ribosome consist of two unequal parts (i.e.
large dome shaped part and small cap like part
which is attached on surface of dome shaped
part).

95. Centrioles

96. Key Facts About Centrosomes
Cell organelles found in animal cell and lower
plant cells.
Absent in higher plant cells.
Each Centrosome consists of two cylinders like
portions called centrioles.
Each centriole consists of nine parallel triplets
of cylindrical microtubules.
Centrioles replicate during cell division and form
mitotic apparatus and helps in cell division.

97. Vacuole

98. Key facts About Vacuole
 Vacuoles are non protoplasmic liquid filled cavities in
cytoplasm.
Surrounded by a membrane called tonoplast.
Tonoplast is not a true membrane and selectively
permeable in nature.
Plant cells contain a large vacuole which contain cell
sap and act as store house of cell.

99. In plant cells vacuoles also contributed in
defence of plant cell.
After death of plant cell enzymes of vacuoles
released and cause lysis of plant cell.
In animal cells vacuoles are formed at time of
their need.
Vacuoles of animal cells are rich in
hydrolytic enzymes and participated in
digesting foreign material.