This presentation provides brief and relevant description of eukaryotic cell organisation. Well labeled figures and pictorial representations are made to give easy understanding to the readers. References are added at the end of the presentation so the readers can get detailed knowledge from the referred books.
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Eukaryotic cell
1. Organisation of eukaryotic cell
By
Rachana L Patnayak
M.Sc. Medical Biotechnology (previous)
Pt. J.N.M. Medical College
Guided by
Dr. G.K. Sahu
Associate professor
Pt. J.N.M. Medical college
2. Contents
1. Introduction
2. Types of eukaryotic cells
3. Structural organization
a) Nucleus
b) Endoplasmic reticulum
c) Golgi apparatus
d) Mitochondria
e) Plastids
f) Ribosomes
g) Lysosomes
h) Peroxisomes
i) Cytoskeleton
j) Vacuole
4. References
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3. 1. Introduction
Eukaryotes
True Nucleus
•All organisms are built from cells including humans. Thus, cell is the
fundamental unit of life.
• Unicellular or multicellular, for example Protists, Fungi, Plantae and Animalia.
•In eukaryotic cells the cellular DNA is segregated within a defined nucleus, which is
bounded by a double membrane.
•The cytoplasm is extensively compartmentalized through the presence of membrane
bound organelles.
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4. Figure 1: Electron micrograph of a plasma cell. Only a single membrane surround the cell
but the interior contains many membrane- limited compartments , or organelles. [ P. C. Cross
and K. L. Mercer, 1993, Cell and tissue ultrastructure : A functional perspective , W. H.
Freeman and company.]
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6. 3. Structural components
a) Cell membrane
• Separates the cell from external environment.
• It has high selective permeability.
• The most accepted model explaining the structure of cell membrane is fluid mosaic model,
proposed by Singer and Nicolson (1972).
• Plays role in various cellular activities, such as signal transduction, membrane trafficking as
well as energy conversion.
Figure 2: Fluid mosaic model of plasma membrane
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7. b) Nucleus
• The nuclear envelope encloses the DNA and defines the nuclear compartment.
• This envelope consists of two concentric membranes that are penetrated by nuclear
pore complexes (NPC).
• Small round granular structure is present- called nucleolus.
• Functions:
- Controls cellular activities like metabolism, protein synthesis, growth
and reproduction (cell division).
- Synthesize RNA.
- Storage of hereditary information.
Figure 3: Electron micrograph of a thin section of
a bone marrow stem cell [ From P.C. Cross and
K.L. Mercer, 1993, Cell and tissue Ultrastructure,
W. H. Freeman and Company].
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8. (c) Endoplasmic reticulum
• An extensive network of interconnecting membranes enclosing channels or
cisternae.
• Two types:
Rough endoplasmic reticulum (RER)
Smooth endoplasmic reticulum (SER)
• Functions:
SER- Synthesis of fatty acids and phospholipids.
- Catabolism and detoxification of toxic substances.
RER- Synthesis of proteins.
Figure 4: Diagrammatic view of Endoplasmic reticulum.
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9. (d) Golgi apparatus
• Three- dimensional reconstruction reveals Golgi apparatus to be a series of
flattened membrane vesicles or sacs (cisternae), surrounded by vesicles.
• The stack of Golgi cisternae has three defined regions- the cis, the medial and the
trans.
• Functions:
-Processing of materials.
-Packaging of materials.
-Labeling and delivery of materials.
Figure 5: Golgi apparatus
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10. (e) Mitochondria
• The mitochondrion (plural=
mitochondria) is a membrane bound
cytoplasmic organelle.
• Functions:
−Production of energy
−Synthesis of ATP
−Apoptosis
−Other functions like storage of
calcium and detoxification of
ammonia in liver.
Hey! I’m also the site for
your heme group synthesis..
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11. (f) Plastids
• Family of self reproducing organelles bounded by a double membrane and
containing a small genome that encodes some of their proteins.
• Based on the type of pigments, they are classified as follows:-
Plastids
Chloroplasts Chromoplasts Leucoplasts
•Contain
chlorophyll and
carotenoid
pigments.
•Sites of CO2
assimilation.
•Fat soluble carotenoid
pigments present.
•Gives part of plant
yellow, orange or red
colour.
•Protects against photo-
oxidation.
•Colourless plastids.
Amyloplasts
Elaioplasts
Aleuroplasts
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12. Figure 7: Plastids- their origins and interconversions
Figure 10: Amyloplasts filled with starch granules
Figure 8: Sectional view of chloroplasts.
Figure 9: Chromoplast of red pepper
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13. (g) Ribosomes
• These are organelles without limiting membrane, are granular and small dot like
structures with a diameter of 15nm.
•They are made up of proteins (15%) and RNA (65%).
•Formed of two subunits- one large subunit and another small subunit.
−In prokaryotes- 70S (50S and 30S)
−In eukaryotes- 80S (60S and 40S)
•Types:
−(i) Bound ribosomes- Attached to rough endoplasmic reticulum.
−(ii) Free ribosomes- Distributed in the cytoplasm
•Function:
−Play role in protein synthesis.
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14. (h) Lysosomes
•Intracellular membrane close compartment in which the composition of the lumen
differs substantially from that of the surrounding cytosol.
•The process by which an aged organelle is degraded in a lysosome is called
autophagy.
•Lysosomes contain a group of hydrolytic enzymes, known as acid hydrolaxes that
degrade polymers into their monomeric subunits.
Figure 11: Cellular structures that participate in
delivering materials to lysosomes.
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15. (i) Peroxisomes
•These are a class of roughly spherical organnels 0.2- 0.1 μm in diameter.
•Contains enzymes such as catalase, peroxidase.
•Functions:
−Perform β- oxidation process.
−Degradation of toxic substances.
−Form the major site of oxygen utilization in the cells.
−Accelerate gluconeogenesis from fats.
−Participate in the formation of myelin.
−Play a role in formation of bile acids.
Figure 12: Peroxisome
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16. (j) Cytoskeleton
• It is a complex network of structures of various sizes present throughout the
cytoplasm.
• Consists of three major protein components, viz :
1. Microtubules
− Straight, hollow and tubular organelles without
limiting membrane.
− Determine the shape of the cell
− Form spindle fibers
2. Intermediate filaments
− Form a network around the nucleus and
extend to the periphery of the cell.
− Helps to maintain the shape of the cell
3. Microfilaments
− Long and fine thread like structures
− Give structural strength to the cell
− Are responsible for cellular movements
Figure 13: A= Microtubules. B= Intermediate
filaments. C= Microfilaments.
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17. (k) Vacuole
• Membrane bound space found in the cytoplasm.
• Mostly found in plant cells and fungi. However animal cells and protists also
contain vacuoles.
• The vacuole is bound by a single membrane called tonoplast.
• Functions:
─Turgor pressure control
─Storage
─Molecular degradation and detoxification
Figure 14: Vacuole of a plant cell
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18. 4. References
1. Cooper GM. The Cell: A Molecular Approach. Sinauer associates; 2013; 355-
382, 529- 537.
2. Lodish H, Berk A, Zipursky SL, Matsudaira P, Baltimore D, Darnell J.
Molecular cell biology. New York: Scientific American Books; 1995; 165-178.
2. Nelson DL, Lehninger AL, Cox MM. Lehninger Principles Of Biochemistry.
Macmillan; 2008; 708.
3. Sembulingam K, Sembulingam P. Essentials Of Medical Physiology. New
Delhi: Jaypee Brothers Medical Publishers (P) ltd; 2010; 4-19.
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Living organisms are highly diverse, and the results obtained from a particular experimental analysis may depend on the particular organism being stud- ied. As a result, cell and molecular biologists have focused considerable research activities on a small number of “repre- sentative” or model organisms. It is hoped that a compre- hensive body of knowledge built on these studies will provide a framework to understand those basic processes that are shared by most organisms, especially humans. This is not to suggest that many other organisms are not widely used in the study of cell and molecular biology. Neverthe- less, six model organisms—one prokaryote and five eukary- otes—have captured much of the attention: a bacterium, E. coli; a budding yeast, Saccharomyces cerevisiae; a flowering plant, Arabidopsis thaliana; a nematode, Caenorhabditis ele- gans; a fruit fly, Drosophila melanogaster; and a mouse, Mus musculus. Each of these organisms has specific advantages that make it particularly useful as a research subject for an- swering certain types of questions.
Refer to Sembulingam pg. 8
RER- vesicular or tubular in structure
SER- formed by many interconnected tubules.
