This document provides information about eukaryotic cell origin, structure, and function. It discusses how eukaryotic cells originated from prokaryotic cells through endosymbiotic theory. Eukaryotic cells have membrane-bound organelles like the nucleus, mitochondria and chloroplasts that allow for more complex structures and functions compared to prokaryotic cells. The document describes the key components of plant and animal cells including their cell membranes, cytoplasm, organelles, and differences between the two cell types.

1. .
Eukaryotes cell origin, structure
and function
Dr. Ganga Naik. S
1st Year Ph.D
Department of Anatomy
Veterinary College
Hebbal, Bangalore -24

2. .
 Origin of life - Prokaryotes and Eukaryotes
 Difference between prokaryotes and
eukaryotes
 Different kind of eukaryotes - Cell structure
and function

3. almost 2 billion
years of strictly
unicellular life!

4.  Our understanding of the origin of life is
• .
incomplete
 Hypothesis that organic molecules formed
spontaneously and evolved into molecular
systems with the fundamental properties of life

5. Many laboratory experiments lend support to
an • abiotic origin of life through chemical
.
evolution

6. .
Miller–Urey experiment
• Demonstrated that most amino acids, were shown to be
racemically synthesized in conditions thought to be similar to
those of the early Earth.
• racemically - relating to, or constituting a compound or

7. .
Endosymbiotic theory
Konstantin Mereschkowski in 1905.
 According to this theory, certain organelles
originated as free-living bacteria that were taken
inside another cell as endosymbionts.

8. .
Endosymbiotic theory
 Mitochondria developed from proteobacteria
(Rickettsiales)
chloroplasts from cyanobacteria.

9. .
Endosymbiotic theory
Many separate organisms may have contributed
for development of cenancestor (
most recent common ancestor).

10. EARLIEST LIFE
• .
Life arose - 3.8 billion years ago
The earliest cells were prokaryotic

11. Prokaryotes
Contains
1. Nucleoid region – Contain
DNA
2. Cell membrane & Cell wall
3. Ribosomes

12. Ancient prokaryotes from
Western Australia.
Filamentous “Cyanobacteria”
3.5 BYA

13. Earliest filamentous
microfossils 3.23 BYA
FROM: Rasmussen 2000 NATURE

14. Microfossil Cyanobacteria

15. Evolution of Eukaryotes
• As early as 2.1 Bya eukaryotic cells appear as
fossils
Figure 01A: Microfossils of Figure 01B: Microfossils of Figure 01C: Microfossils of
probable eukaryotic cells probable eukaryotic cells probable eukaryotic cells
Reproduced from Schopf, J.W., Scientific American 239 (1978): 111-138. Courtesy of J. William Schopf, Professor of Paleobiology &
Director of IGPP CSEOL

16. Origin of the Eukaryotes
 Two theories to explain the origin of
membrane bound organelles
1. Endosymbiosum
2. Invagination

17. • .

18. .
• .

19. Origin of the Eukaryotes

20. .
• .

21. Eukaryotes cells
NUCLEUS
CYTOSKELETON
RIBOSOMES
MITOCHONDRION ROUGH ER
CYTOPLASM SMOOTH ER
CENTRIOLES
GOLGI BODY
PLASMA LYSOSOME
MEMBRANE
VESICLE

22. Differences between Prokaryotic Cells and
Eukaryotic cells
Prokaryotic Cells Eukaryotic cells
small cells (< 5 mm) larger cells (> 10 mm)
always unicellular often multicellular
no nucleus or any membrane-bound always have nucleus and other
organelles membrane-bound organelles
DNA is circular, without proteins DNA is linear and associated with
proteins to form chromatin
ribosomes are small (70S) ribosomes are large (80S)
no cytoskeleton always has a cytoskeleton
cell division is by binary fission cell division is by mitosis or
meiosis
reproduction is always asexual reproduction is asexual or sexual

23. Eukaryotes
Include most cells (other than bacteria)
1.Plants
2. Fungi

24. Eukaryotic Cell
Contain 3 basic cell
structures:
1.Nucleus
2.Cell Membrane
3.Cytoplasm with
organelles

25. Types of Eukaryotic Cells
Animal Cell
Plant Cell

26. Plant Cell
• Cell wall
Made of cellulose which
forms very thin fibers
Gives shape to the cell

27. Plant Cell
• Cell membrane
– Lies immediately against
the cell wall
– Made of protein and lipid
∴Selectively permeable

28. Plant Cell
• Cytoplasm
– Jelly-like substance
enclosed by cell membrane
– Contains organelles and
granules
•e.g. chloroplast
•e.g. mitochondrion

29. Plant Cell
Nucleus
– Bounded by a
nuclear membrane
– 1.Controls the normal
activities of the cell
2. For heredity
– Contains thread-like chromosomes

30. .
Animal cell

31. Animal cell
 No cell wall and chloroplast
 Small vacuoles
 Stores glycogen granules and oil droplets
in the cytoplasm

32. Animal cell
vacuole cytoplasm
nucleus
glycogen
granule
cell
mitochondrion
membrane

33. Different kinds of animal cells
white blood cell
Amoeba
red blood cell
muscle cell
sperm
cheek cells
nerve cell
Paramecium

34. Structure Animal cells Plant cells
cell membrane Yes yes
nucleus Yes yes
nucleolus yes yes
ribosomes yes yes
ER yes yes
Golgi yes yes
centrioles yes no
cell wall no yes
mitochondria yes yes
cholorplasts no yes
One big vacuole no yes
cytoskeleton yes Yes

35. Cytoplasm
.
 involved in
1. Energy formation and release
2. Protein synthesis

36. Cytoplasm
.
• Subdivided into
1.Cytocentrum
2. Endocentrum
3.Ectoplasm

37. Cytoplasm
.
1.Cytocentrum
• ER
• Pair of centriole
• Cytoskeletal
element

38. Cytoplasm
.
2.Endocentrum
• Largest
• Most of structural
components

39. Cytoplasm
.
3. Ectoplasm
• Narrow band

40. PLASMA MEMBRANE
/Cell membrane
 Surrounds the entire cytoplasm
 Provides a selective barrier
 regulates the transport of materials into
and out of the cell.

41. PLASMA MEMBRANE
/Cell membrane
All membranes including the membranous
organelles are composed
1. Lipid and protein - mainly
2. Carbohydrate - small amount

42. Organelles
1. Rough Endoplasmic Reticulum
2. Smooth Endoplasmic Reticulum:
3. Golgi Complex:
4. Mitochondria:
5. Lysosomes:
6. Peroxisomes Or Microbodies:

43. Cytoskeletal
Elements And
Cytoplasmic
Matrix
a) Microtubules:
b) Centrioles Or
Diplosomes
c) Microfilaments:

44. NUCLEUS
 The nucleus is found in all cells except
mammalian red blood cells and platelets,

45. NUCLEUS
 It has DNA,
which is the storehouse of genetic information
 controls protein synthesis in the cells.

46. Granular endoplasmic reticulum /
,
Rough endoplasmic reticulum /
Ergatoplasm /
chromidial substance:

48. Granular endoplasmic reticulum
The membrane bound channels are either
a. Cistarnae (flattened sacs)
b. Tubular or
c. Vesicles

50. .
Granular endoplasmic reticulum
Ribosomes
 are Rnp granules (Ribonuclear
protein),
the sites of synthesis of proteins from
amino acids.

51. Functions:
1. Contributed to the mechanical support of
cytoplasm
2. Synthesis of proteins for export

52. Ribosomes:
.

53. Ribosomes:
Occur in two forms.
1. Associated with endoplasmic reticulum
2. Occur free in cytoplasm

54. Ribosomes:
• Under E/M appear as small electron dense
particles 150Ǻ diameter formed by 2 subunits one
large and one small.

55. Several ribosomes associated with
endoplasmic reticulum synthesis proteins,
These proteins are meant for external
use.
Eg. Enzymes.

56. • Several ribosomes are attached to each other by a
strand of mRNA forming polysomes or
polyribosomes.

57. Polyribosomes
 Synthesize proteins
 intracellular use
Eg. Hemoglobin formed in red blood cells.

58. :
SMOOTH ENDOPLASMIC
RETICULUM

59. SMOOTH ENDOPLASMIC RETICULUM:
 Under electron microscope appear as three
dimensional network of membrane bound
tubules with no cisternae and lack ribosomes.
 It may communicate with RER or with
nuclear envelope.

60. .
• .

62. Functions:
 Production of steroid hormone, in
steroid secreting cells, adrenal cortex,
testes, ovary.

63. GOLGI COMPLEX:

64. GOLGI COMPLEX:
• Supranuclear position in secreting cells

65. .
• E/M appear as lamellae (3-12 in number) of
parallely arranged flattened curved membranous
sacs, vacuoles or vesicles.

66. Function:
 Condensation and packing of secretory product by
loss of water.

67. MITOCHONDRIA:
.

68. MITOCHONDRIA: .
• Energy conversion system by
which chemical energy of food
stuffs is converted into high energy
phosphates (ATP)

69. MITOCHONDRIA:
.

70. E/M –
 Double membranous structure with
rounded ends or sausage shaped.

71. Mitochondrial matrix .
 Electron dense granules
 DNA and RNA strands

72. .
Mitochondrial matrix
DNA and RNA strands
• which directs the synthesis of enzymes of
mitochondria.

73. Function – synthesis of ATP
3 major pathways involved in ATP production
1. Glycolysis .
2. Krebs Cycle
3. Electron transport system .(ETS)
• .

74. .
LYSOSOMES

75. LYSOSOMES
Membrane bound spherical uniformly
granular electron dense bodies.

76. LYSOSOMES
Present in all cells
 but numerous in cells exhibiting phagocytic
activity.
E.g. Macrophages and WBC’s.

77. LYSOSOMES
• Associated with intracellular digestion and
phagocytosis.

78. LYSOSOMES
• Contain more than 40 hydrolytic enzymes
• active at acid pH.
Eg. Acid phosphatase, Ribonuclease, sulphatase etc.

79. • .
PEROXISOMES OR MICROBODIES:

80. PEROXISOMES OR MICROBODIES:
• Membrane bound bodies
•

81. PEROXISOMES OR MICROBODIES:
• Resemble lysosomes
• but do not contain lysosomal enzymes.

82. PEROXISOMES OR MICROBODIES:
Function :
 Hydrogen peroxide is detoxified
 Fatty acids are metabolized

83. .
CYTOSKELETAL ELEMENTS
AND
CYTOPLASMIC MATRIX

84. .
CYTOSKELETAL ELEMENTS
• Structure
Interconnected system of
– microtubules,
– microfilaments,
– intermediate filaments

85. .
CYTOSKELETAL ELEMENTS
• Function
– gives cells internal organization, shape, and ability to
move

86. CYTOSKELETAL ELEMENTS AND CYTOPLASMIC
MATRIX
MICROTUBULES:
 Slender, hollow, cylindrical un
branched structures
 Made of tubulin proteins (globular)
•

87. CYTOSKELETAL ELEMENTS AND CYTOPLASMIC
MATRIX
MICROTUBULES:
Function
 Separation of chromosomes during mitosis.

88. • .
CENTRIOLES (Diplosome):

89. CENTRIOLES (Diplosome):
• A is a cylindrically-shaped cell structure

90. CENTRIOLES (Diplosome):
• Wall is composed of 9 sets of microtubule triplets.

91. CENTRIOLES (Diplosome):
Functions:
 involved in the organization of the mitotic spindle
 in the completion of cytokinesis

92. •.
MICROFILAMENTS:

93. MICROFILAMENTS:
1. Actin - 70A°
2. Myosin - 150 A°.
• In muscle cells well organized filamentous
components.

94. MICROFILAMENTS:
Functions:
Enable cells to change shape and move
(Participate in muscle contraction)

95. MICROFILAMENTS:
Functions:.
Provide contractile forces to form
cleavage furrow during cell division.

96. Cilia and flagella (structures for cell motility)
– Move whole cells or materials across the cell surface
– Microtubules wrapped in an extension of the plasma
membrane (9 + 2 arrangement of MT)

97. Thank you