The presentation includes the basics of cell: Definition, criteria for defining a cell, differences between prokaryotic cells and eukaryotic cells, plat and animal cells, structure and function of organelles, symbiont theory and MCQs.

1. Ms. Jigisha Pancholi
Head
Dept. of Biochemistry &
Microbiology
Indian Institute of
Ayurvedic Pharmaceutical
Sciences
Gujarat Ayurved University
Jamnagar

2. CONTENTS
 Introduction
 Criteria for defining a cell
 Cell theory
 Types of cells
 Differences between prokaryotes and
eukaryotes
 Differences between animal and plant cells
 Symbiont theory

3.  Structure and functions of:
Nucleus, Endoplastic reticulum, Ribosomes,
Mitochondria, Lysosomes, Golgi apparatus,
Chloroplast, Centrioles, Cell wall, Peroxisome,
Glyoxisome, Cell membrane, Vacuoles,
Cytoskeleton
CONTENTS

4.  Cell is the fundamental and basic unit of life.
 All living systems are composed of cells.
 Robert Hook was the first to discover cell in the
bark of cork tree.

5. CRITERIA FOR DEFINING A CELL
 Cell should have a specific genetic material which
permits reproduction of new cells of same type.
 A cell membrane should be present which forms a
selective boundary regulating all exchanges of
matter.
 Catabolic machinery should be present to break
down food material to obtain required
metabolites and energy.
 Cell should possess biosynthetic machinery for
synthesizing bio molecules.

7. CELL THEORY
 It is a scientific theory that describes properties of
cells.
 The observations of Hooke, Leeuwenhoek,
Schleiden, Schwann, Virchow and others led to the
development of the cell theory.
 The cell theory states:
All living things or organisms are made of cells
New cells are created by old cells dividing into two
Cells are the basic building units of life

8. TYPES OF CELLS
 Prokaryotic cells: No nucleus but has single
circular chromosome , without histone proteins.
 Mesokaryotic cells: Intermediate type of nucleus
with multiple chromosomes, without histone
proteins.
 Eukaryotic cells: well defined nucleus with
multiple chromosomes, with histone proteins.

9. PROKARYOTIC CELL
 Lack nucleus and other organelles
 Have single circular chromosome
 DNA not bound to histone proteins
 Possess 70 S ribosome
 Cell wall made up of peptidoglycan and
lipopolysaccharide
 Metabolism: aerobic and anaerobic
 Prokaryotes are divided into two domains: Archaea
and Eubacteria
 Example: All the bacteria like E. Coli,
Staphylococcus, Salmonella etc.

11. MESOKARYOTIC CELL
 Contain an intermediate type of nucleus.
 Have multiple chromosomes but they remain
permanently condensed
 DNA not attached to histone proteins.
 The mesokaryotic nucleus does not divide as a
eukaryotic cell's does; instead, it duplicates itself,
with one nucleus going with each cell half when
the rest of the cell divides.
 Example: Dinoflagellates

13. EUKARYOTIC CELL
 Cells have well defined nucleus and organelles.
 Can be both unicellular and multicellular.
 Have multiple chromosomes
 DNA bound to histone proteins
 Possess 80 S and 70 S ribosomes (mitochondria
and chloroplast)
 Cell wall present in plants, fungi and algae.
Animal cells don’t have cell wall.
 Metabolism : Aerobic
 Example: All the animals, plants, amoeba,
plasmodium, mushroom, algae etc.

14. PLANT CELL

15. ANIMAL CELL

16. DIFFERENCES BETWEEN PROKARYOTES
AND EUKARYOTES
Properties Prokaryotes Eukaryotes
Nuclear Membrane Absent Present
Organelles Absent Present
DNA Naked Bound to histones
Chromosomes Single Multiple
Nucleolus Absent Present
Ribosomes 70 S 80 S(except
mitochondria and
chloroplast)
Cell division Amitotic Mitotic and meiotic
Cell wall Made up of
peptidoglycan and
lipopolysaccharides
Present in plants,
fungi and some
protists. In plants
made up of cellulose

17. Properties Prokaryotes Eukaryotes
Exocytosis and
endocytosis
Absent Present
Pilli Present Absent
Capsule Present Absent
Cytoskeletal network Absent Present
Metabolism Aerobic and
anaerobic
Aerobic
Cellular respiration Occurs in cell
membrane
Occurs in
mitochondria
Processing of RNA To little extent To greater extent
Transcription and
translation
In cytoplasm In nucleus and RER
respectively
Cell size 1- 10 um 10 -100 um
Example Bacteria,
archeabacteria
Plants, animals,
yeast, fungi

18. DIFFERENCES BETWEEN PLANT AND
ANIMAL CELLS
Plant cell Animal cell
Possess cell wall Cell wall absent
Contain chloroplast Chloroplast absent
Can do photosynthesis Cannot do photosynthesis
Glyoxysomes present Glyoxisomes absent
Cells are totipotent Cells are not totipotent
Starch is the storage form
carbohydrates
Glycogen is the storage form of
carbohydrates
A large sized central vacuole
present
Central vacuole absent
Presence of lysosomes is rare Lysosomes present
Centrioles present only in lower
plant, not in higher plants
Centrioles present in all animal
cells

19. QUESTIONS
 Cellular totipotency is demonstrated by:
a. Only bacterial cell
b. Only gymnosperm cell
c. all plant cells
d. All eukaryotic cells
 Which of the following is not found in prokaryotic
cell?
a. Plasma membrane
b. Cell wall
c. Nuclear envelop
d. Ribosomes

20. QUESTIONS
 The cell is the basic unit of structure of living
things was discovered by:
a. Aristotle
b. Robert Hooke
c. Gregor Mendel
d. Shwann and Shleiden
 A human egg is very large compared to human
sperm due to:
a. Nucleus
b. Membranes
c. Cytoplasm
d. Both a and c

21. NUCLEUS
 Largest organelle of the cell and spherical in
shape.
 Robert Brown in 1831 discovered nucleus.
 Most eukaryotic cells have single nucleus, fungi
has multiple nucleus.

22. STRUCTURE OF NUCLEUS
 Two membranes:
Outer membrane + Inner membrane  Nuclear
envelope.
 Outer membrane is continuous with R.E.R.
 Nuclear pore complex located at 50 – 80 nm
apart.
 Nuclear pore are made up of proteins, facilitates
transport of molecules.

23.  Genetic material is present in the form of
chromatin/ chromosomes.
 Dense and spherical Nucleolus is the site of
rRNA synthesis.
 Nucleoplasm is the fluid inside the nucleus.

24. FUNCTIONS OF NUCLEUS
 Contains DNA that is genetic material inherited
in the offspring from parents.
 Control center or brain of the cell.
 Required for long term survival of the cell.
 Nucleolus is the site for the synthesis of r RNA.
 DNA replication and RNA transcription occurs in
the nucleus.

25. ENDOPLASMIC RETICULUM
 Endoplasmic means ‘within the cytoplasm’ and reticulum is
‘net’.
 Forms an interconnected network of tubules, vesicles and
cisternae.
 The term endoplastic reticulum was first used by Porter
and Kallman in 1952.
 Two types:
Rough Endoplasmic Reticulum: Contains ribosomes
Smooth Endoplasmic Reticulum: Does not contain
ribosomes.

26. R.E.R. S.E.R.

27. FUNCTIONS OF ENDOPLASMIC RETICULUM
Rough Endoplasmic Reticulum
 Site for protein synthesis.
 Folding of newly formed peptide chain by
chaperone proteins.
 Glycosylation of proteins.
Smooth Endoplasmic Reticulum
 Lipid and steroid synthesis.
 Drug detoxification
 Sarcoplasmic reticulum stores calcium and
promotes muscle contraction.

28. RIBOSOMES
 Ribosomes are made up of RNA and Proteins
 They are negatively charged
 Do not have a membrane
 Discovered by Palade and so called ‘Palade particles’
 Can be either bound to E.R. or is in the soluble form
in cytoplasm
 Has small and large subunits, attached at a critical
concentration of Mg2+
 Two types:
70 S- In prokaryotes, mitochondria and chloroplast
80 S- In eukaryotes

29. QUESTIONS
 How many membranes make the nuclear
envelope?
a. 1
b. 2
c. 3
d. None
 The principal site for synthesis of r RNA is:
a. Mitochondria
b. Golgi bodies
c. Nucleolus
d. Lysosomes

30. QUESTIONS
 The major site for synthesis of lipids is:
a. SER
b. Nucleoplasm
c. RER
d. Mitochondria
 The main organelle involved in modification and
routing of newly synthesized proteins to their
destinations is:
a. Mitochondria
b. ER
c. Lysosome
d. Chloroplast

31. QUESTIONS
 Which of these organelles does not have a
membrane?
a. Ribosome
b. Nucleus
c. Chloroplast
d. Mitochondria
 The two subunits of ribosomes remain united at a
critical level of:
a. Calcium
b. Copper
c. Manganese
d. Magnesium

32. QUESTIONS
 What will happen if nucleus is removed?
a. Metabolism will increase
b. Cell will die
c. Metabolism will decrease
d. None of the above

33. MITOCHONDRIA
 Tubular or sausage shaped organelles, shape
may vary to spherical, loop, rod or filamentous
 Called as ‘power house of cell’
 Plants have less number of mitochondria than
animal cells

34. STRUCTURE OF MITOCHONDRIA
 Membrane : Outer membrane (Smooth)
Inter membrane space
Inner membrane (Folded to form cristae)
Matrix
DNA
70 S ribosome
F1 – Fo ATPase

35. FUNCTIONS OF MITOCHONDRIA
 F1- Fo ATPase by oxidative phosphorylation
synthesizes ATP.
 Site for many metabolic processes like TCA,
gluconeogenesis, oxidation of lipids etc.
 Involved in apoptosis.
 In brown adipose tissue of hibernating animals,
by the action of thermogenin produces heat.

36. LYSOSOMES
 Unit membrane bound digestive vesicles contain
high levels of degrading enzymes like nuclease,
lipase, amylase, protease, phospholipase,
esterase etc.
 Called as ‘suicidal bags’
 Breaks down proteins, nucleic acids, lipids and
carbohydrates.

37.  Size varies from 01- 1.2 um.
 Enzymes work in acidic pH 4.5.
 Low pH maintained within lysosomes by
pumping protons in.
 Lysosomal enzymes are synthesized by soluble
ribosomes in cytoplasm and on R.E.R.
 The leader sequence in enzymes targeted for
lysosome is Mannose -6- phosphate.

38. FUNCTIONS OF LYSOSOME
 Degrade food molecules obtained by phagocytosis or
endocytosis.
 Digest foreign antigens entering inside the cell.
 Hylauronidase enzyme from lysosome of sperm digest
the limiting layer around ovum and facilitate
fertilization.
 For transformation from tadpole to frog.
 Degrade worn out and un needed organelles.
 Involved in autophagy required for growth,
development and during starvation.

39. GOLGI APPARATUS
 These are flattened stacks of membranes, often
interconnected with one another.
 Were discovered by Camillo Golgi, the Italian
Physician.
 Number varies in a cell from 1 or few in protists, 20 or
more in animal cells and hundreds in plant cells.
 Especially abundant in glandular cells.
 Golgi bodies are collectively called as Golgi apparatus.

40. STRUCTURE OF GOLGI BODIES
 It is composed of individual flattened
membranous structures called cisternae.
 Components of Golgi include:
 Cis cisterna (Near E.R.)
 Medial cisterna (Between cis and trans)
 Trans cisterna (Near Cell membrane)
 Golgi vesicles (Transports molecules)

43. FUNCTION OF GOLGI APPARATUS
 Packaging of secretory molecules into vesicles
and target to the cell membrane for secretion.
 Glycosylation of proteins and lipids.

44. QUESTIONS
 Which of these cellular organelles breaks down
cell and foreign particles of a cell?
a. Golgi complex
b. Lysosome
c. Mitochondria
d. RER
 Within the cell, the site of the respiration is:
a. Nucleus
b. Mitochondria
c. Lysosome
d. Ribosome

45. QUESTIONS
 Important site for the formation of glycoproteins
and glycolipids is:
a. Vacuole
b. Golgi apparatus
c. Lysosome
d. RER
 Lysosomes are considered as suicidal bags
because they:
a. Kill neighbouring cells
b. Kill engulfed bacteria
c. Are responsible for intracellular digestion
d. Oxidize food in the cells

46. CHLOROPLAST
 In Greek, ‘chloros’ means green and ‘plast’ means
form or entity.
 Flat discs usually 2- 10 um in diameter and1 um
thick. In land plants 5 um and 2.3 um thick.
 A typical parenchyma cell contains about 10 -100
chloroplasts.

48. STRUCTURE AND FUNCTION OF
CHLOROPLAST
 Chloroplast membrane: Outer membrane
Inter membrane space
Inner membrane
 Grana / Granum made up of thylakoids
 Chlorophyll on the surface of thylakoids.
 Stroma
 DNA
 70 S ribosome
Synthesizes ATP by reduction of NAD through
the process of photosynthesis
Synthesizes ATP by reduction of NAD through the process
of photosynthesis

49. SYMBIOSIS THEORY OR SYMBIONT
THEORY
 Given by Lynn Margulis.
 For the origin of mitochondria and chloroplasts
into the eukaryotic cells.
 These were free living aerobic prokaryotes that
invaded other prokaryotic anaerobic cells early in
the evolution of life.
 These two obtained proteins, nutrients and other
bio molecules from the host cells and host cells
got energy from these invading organisms.

50. SUPPORTIVE EVIDENCE FOR SYMBIONT
THEORY
 The cell membrane is similar in composition to
that of prokaryotic cell.
 Contain their own DNA that occurs in simple,
circular strands as DNA of prokaryotes.
 The genetic code of their DNA is slightly different
from that of chromosomal DNA.
 The mitochondria and chloroplast can reproduce
and multiply by themselves.

51. CENTRIOLES
 Barrel shaped organelles.
 Found in animals and protists.
 Plants do not have centrioles except algae.
 They occur in pairs, at right angles to each other
near the nucleus.
 They are made up of microtubules.

52. FUNCTIONS OF CENTRIOLES
 Cell division: forms spindle fiber during mitosis
and meiosis.
 Celiogenesis: process of formation of cilia and
flagella.
 Sperm tail formation: helps in the formation of
tail fiber of the spermatozoa.

53. CELL WALL
 Thick and hard covering surrounding the cell
membrane.
 Present in plants, fungi, algae, some protists and
bacteria.
 Not present in animal cells.
PLANT CELL WALL
 Made up of cellulose, hemicellulose, pectin and
lignin.
 Has minerals like calcium and magnesium in the
form of carbonates and silicates.

54.  Three parts:
Primary cell wall: outermost layer, thin, permeable
and composed of cellulose, hemicellulose, pectin and
lignin.
Secondary cell wall: thick, permeable, lies near the
plasma membrane and has cellulose, hemicellulose,
lignin and sometimes has xylem.
Tertiary cell wall: some plants have it which is in the
interior most side of the cell wall.
 Middle lamella joins the two cells, gummy
intracellular matrix, rich in pectin.

56. FUNCTIONS OF CELL WALL
 Provides shape and strength to the cell.
 Protects cell from mechanical and osmotic
rupture.

57. QUESTIONS
 Which of the following sets of organelles have
DNA?
a. Mitochondria, ribosomes, chloroplast
b. Nucleus, ribosomes, chloroplast
c. Nucleus, ribosome, mitochondria
d. Nucleus, mitochondria, chloroplast
 Chlorophyll in chloroplast is present in:
a. Membrane
b. Thylakoid
c. Stroma
d. Both grana and stroma

58. QUESTIONS
 Centrioles are:
a. Cylindrical structures
b. Rectangular structures
c. Cuboidal structures
d. Square structures
 Cell wall of plants is made up of:
a. Chitin
b. Lipids
c. Xylan
d. Cellulose

59. PEROXISOMES
 Present in almost all eukaryotic cells.
 Identified as organelles by Belgian cytologist
Christian de Duve in 1967.
 Participate in the metabolism of fatty acids and
many other metabolites.
 They have enzymes that remove toxic peroxides.
 Single membrane structure.

60. FUNCTIONS OF PEROXISOMES
 They have oxidative enzymes such as catalase, D-
amino acid oxidase and uric acid oxidase. The
generation and breakdown of H2O2 occurs in
peroxisomes.
RH2 + O2 ----------- > R +H2O2
H2O2 + R’H2 ----------- > R’ + 2H2O
2H2O2 ------------ > 2H2O + O2
 Involved in breakdown of fatty acid molecules
through beta- oxidation. In animal cells, it also
occurs in mitochondria but in yeast and plant
cells, it exclusively occurs in peroxisomes.

61. GLYOXISOMES
 These are specialized form of peroxisomes.
 Found in yeast and oil rich seeds of many higher
plants.

62. FUNCTIONS OF GLYOXISOMES
 Site for glyoxylate pathway. During germination
of oil rich seeds, the stored lipid molecules are
hydrolyzed by lipases to glycerol and fatty acids.
Glycerol through gluconeogenesis is converted to
glucose which is utilized by the seedling.

63. CELL MEMBRANE
 Separates the cell from the external environment.
 Made up of lipids, proteins and small amount of
carbohydrates.
 Has fluid mosaic model proposed by ‘Sanger and
Nicholson’
 Is hydrophilic from outer and inner side and has a
hydrophobic core
 Shows selective permeability

65. LIPIDS
 The lipid bilayer shows free lateral movement of its
compounds, hence the membrane is said to be fluid in
nature.
 Lipids in membrane are: Phospholipids
Glycolipids
Cholesterol
 Phospholipids are the most common lipids present and
they are amphipathic in nature.
 The phospholipids are arranged in bilayers with the
polar head groups oriented towards the extracellular
side and the cytoplasmic side with a hydrophobic core.

66.  Cholesterol maintains fluidity of the membrane.

67. PROTEINS
 Proteins form the mosaic part in the membrane.
 Two types:
1. Integral Proteins- they pass through the membrane. Some
proteins span the whole membrane called transmembrane
proteins.
2. Peripheral Protein-Present either inside or outside the
membrane.
 These proteins act as either adhesion molecules,
carrier proteins, channel proteins, receptors or
enzymes.

68. VACUOLE
 A membrane-bound organelle which is present in
all plant and fungal cells and some protist,
animal and bacterial cells.
 Vacuoles are essentially enclosed compartments
which are filled with water containing inorganic
and organic molecules including enzymes in
solution.
 The organelle has no basic shape or size; its
structure varies according to the needs of the cell.

70. FUNCTIONS
 Isolate materials that might be harmful or a
threat to the cell
 Store waste products
 Store water in plant cells
 Maintain internal hydrostatic pressure or turgor
within the cell. Turgor pressure in a plant cell is
between 5 and 20 atm.

71. CYTOSKELETON
 Skeletal system present inside the cytoplasm.
 In 1903 Nikolai K Koltsov proposed the term
cytoskeleton.
 Types: 1. Microtubule
2. Intermediate filament
3. Microfilament

72. MICROTUBULE
 Long ,hollow structure
 23 nm in diameter
 Made up of two subunits Alpha and Beta tubulin
 They play key roles in:
Intracellular transport
The axoneme of cilia and flagella
The mitotic spindle
Synthesis of the cell wall in plants

73. INTERMEDIATE FILAMENTS
 10 nanometers in diameter
 It may be useful to think of micro- and
intermediate filaments as cables and of
microtubules as cellular support beams.
 Different intermediate filaments are:
 Made of vimentins, being the common structural
support of many cells.
 Made of keratin, found in skin cells, hair and nails.
 Neurofilaments of neural cells.

74. MICROFILAMENTS
 These are the thinnest filaments of the
cytoskeleton.
 About 7 nm in diameter
 They are composed of linear polymers of actin
subunits.
 They also act as tracks for the movement of
myosin molecules that attach to the
microfilament and "walk" along them.

75. CYTOPLASM
 the cytoplasm is the material or protoplasm
within a living cell, excluding the cell nucleus.
 It comprises cytosol (the gel-like substance
enclosed within the cell membrane) and the
organelles – the cell's internal sub-structures.
 The cytoplasm is about 80% water and usually
colorless
 It also contains proteins, of which 20-25 percent
are soluble proteins including enzymes.

76. CYTOPLASM
 The concentrated inner area is called the
endoplasm and the outer layer is called the cell
cortex or the ectoplasm.
 The cytoplasm constitutes of dissolved nutrients
and it aids to dissolve waste products.

77. CYTOPLASM FUNCTIONS
 Cytoplasm is the site of many biochemical
reactions that are vital and crucial for
maintaining life.
 The cytoplasm provides a medium for the
organelles to remain suspended.
 The cytoskeleton of the cytoplasm provides shape
to the cell and it also facilitates movement.

78. CYTOPLASM FUNCTIONS
 It also aids in the movement of the different
cellular elements.
 The cytoplasm acts as a buffer

79. CYTOPLASM FUNCTIONS
 The cytoplasmic organelles are specialized structures
that haves its own functions like cellular respiration,
protein synthesis etc.
 The cytoplasmic inclusions are non-soluble molecules,
they are seen floating in the cytoplasm, they act as
stored fats and sugars that are ready for cellular
respiration.
 The cytoplasm and the proteins prevent the grouping
of organelles in place due to gravity, that would
impede their function.

80. QUESTIONS
 The supporting framework of a cell consists of:
a. Microfilaments
b. Microtubules
c. Both of these
d. None of these
 Peroxisomes are bound by:
a. Single membrane
b. Double membrane
c. Triple membrane
d. No membrane

81. QUESTIONS
 Turgor pressure in plant cells is generally
between:
a. 5 and 20 atm
b. 20 and 40 atm
c. 10 and 30 atm
d. 1 and 5 atm
 Which of these is true for flip flop movement of
membrane lipids and proteins?
a. Both lipids and proteins can flip flop
b. Neither lipids or proteins can flip flop
c. While proteins can, lipids cannot
d. While lipids can rarely flip flop, proteins cannot

82. QUESTIONS
 In germinating seeds, fatty acids are exclusively
degraded in:
a. Mitochondria
b. SER
c. Peroxisomes
d. Glyoxisomes
 The most abundant lipid in plasma membrane is:
a. Phospholipid
b. Cholesterol
c. Steroids
d. Glycolipid

83. QUESTIONS
 According to fluid mosaic model, the fluidity of a
membrane is due to:
a. Lipids
b. Proteins
c. Cholesterol
d. Glycolipids