Post on 08-Apr-2018
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THE CELLTHE CELL
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Aims and Objectives
1. To review and interpret the microanatomy
of human cells as seen under the light andelectron microscope.
2. Give examples to demonstrate the diversity
of cell types in multicellular organisms suchas humans.
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Lecture Outline
Organisation of the cell:
Cytoplasm
Matrix Organelles
Inclusions
Nucleus
Review questions.
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THE CELLTHE CELL
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CELL
Cell is the basic structural and functional unit
of all multicellular organisms
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Cell
Nucleus
Cytoplasmic matrix
Organelles
Inclusions
Cytoplasm
Chromatin
Nucleolus
Nuclear envelope
Nuclear skeleton
Nucleoplasm
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Cell
Nucleus
Cytoplasmic matrix
Organelles
Membranous
Non-membranous
Inclusions Membranous
Non-membranous
Cytoplasm
Chromatin
Nucleolus
Nuclear envelope
Nuclear skeleton
Nucleoplasm
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Cytoplasmic matrix
Organelles Inclusions
CYTOPLASM
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Cytoplasmic matrix
Solution containing electrolytes, metabolites,
RNA and synthesized proteins.
CYTOPLASM
Organelles
Living structures with metabolic/synthetic
functions.
Inclusions
Non-living structures with no metabolic function.
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MEMBRANOUS ORGANELLES
1. Plasma/cell membrane
2. Endoplasmic reticulum
a. Smooth ER
b. Rough ER
3. Golgi apparatus
4. Mitochondria
5. Lysosomes6. Peroxisomes
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Plasma membrane
sER
rER
Mitochondrion
Lysosome
Golgi
apparatus
1. Plasma Membrane
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8-10 nm thick hence not visible with LM.
Trilaminarappearance when seen with TEM
(2 dark lines enclosing a clear band)
1. Plasma Membrane - Appearance
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1. Plasma Membrane - Composition
Proteins:
Integral proteins
(within lipid bilayer)
Peripheral proteins
(bound to surface)
Phospholipids:
Outer portion
(hydrophilic)
Inner portion
(hydrophobic)
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Proteins:
Integral proteins (within lipid bilayer)
Peripheral proteins (bound to surface)
Phospholipids:
Inner portion (hydrophobic)
Outer portion (hydrophilic)
1. Plasma Membrane - Composition
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Glycocalyx:
A layer of glycoprotein-glycolipid molecules that covers the membrane.
Protects the cell from chemical/physical injuries
.
1. Plasma Membrane - Composition
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Cell Junctions
Gap Junctions
Forjoining with adjacent
cells (to form tissues)
Allow communication
between adjacent cells.
1. Plasma Membrane - Modifications
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Gap Junctions
Consist of manycommunicating channels.
2 closely apposed plasma
membranes, 2nm apart.
Communication betweencytoplasmic compartments
of adjacent cells allow direct
passage of ions and small
molecules.
connexion
1. Plasma Membrane - Modifications
Each channel is made up of
2 connexions.
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Maintains the structural integrity of the cell.
Establishes transport system for some molecules.
Controls movements of substances in and out of the cell.
Acts as barrier between cytoplasm and external millieu.
Recognizes antigens, foreign cells, altered cells
(via receptors) Transduces extracellular signals into intracellular events.
Regulates interaction between cells.
1. Plasma Membrane - Functions
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Not visible with LM (8-10 nm thick).
Trilaminar appearance under TEM.
Formed by protein and bilayerphospholipids.
Covered by glycocalyx (a protective layer on its surface)
Cell junctionsjoin adjacent cells.
1. Plasma Membrane - Summary
Gap junctions allow communication betweenadjacent cells for direct passage of ions and
small molecules.
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MEMBRANOUS ORGANELLES
1. Plasma/cell membrane
2. Endoplasmic reticulum
a. Smooth ER
b. Rough ER
3. Golgi apparatus
4. Mitochondria
5. Lysosomes6. Peroxisomes
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Plasma membrane
sER
rER
Mitochondrion
Lysosome
Golgi
apparatus
2. Endoplasmic Reticulum
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sER
rER
A continuous membrane in the form of anastomosing network of tubules
2a. Smooth Endoplasmic Reticulum (sER)
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Devoid ofribosomes (not covered with ribosomes)
A continuous membrane in the form of anastomosing
network of tubules.
Responsible for cytoplasmic eosinophilia
2a. Smooth Endoplasmic Reticulum (sER)
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Particles of ribosomes stud the exterior surface of the membrane (EM)
2b. Rough Endoplasmic Reticulum (rER)
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arrows indicate
clear area
Basophilic part of cytoplasm (ergastoplasm) is the image of rER
2b. Rough Endoplasmic Reticulum (rER)
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cells that contain large amounts ofplasma membrane
(e.g. nerve cells)
cells that synthesize proteins
(e.g. secretory and glandular cells, plasma cells,
fibroblasts, osteoblasts, odontoblasts, ameloblasts)
rERis well developed in:
2b. Rough Endoplasmic Reticulum (rER)
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MEMBRANOUS ORGANELLES
1. Plasma/cell membrane
2. Endoplasmic reticulum
a. Smooth ERb. Rough ER
3. Golgi apparatus
4. Mitochondria
5. Lysosomes6. Peroxisomes
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Under LM, Golgi apparatus is
seen as a large clear area that
is surrounded by the basophilic
ergastoplasm (rER)
arrows indicates the clear area
3. Golgi Apparatus
Functions:
Synthesizes carbohydrate.
Modification, sorting and
packaging of proteins.
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Under EM, Golgi appears as
stacks of flat membrane-bound
sacs lying close to secretory
vesicles.
3. Golgi Apparatus
Functions:
Synthesizes carbohydrate.
Modification, sorting and
packaging of proteins.
cv = condensing vacuole; sv =secretory vacuole;
ff = forming face; mf = maturing face
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sER, rER and Golgi complex
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sER, rER and Golgi complex
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MEMBRANOUS ORGANELLES
1. Plasma/cell membrane
2. Endoplasmic reticulum
a. Smooth ERb. Rough ER
3. Golgi apparatus
4. Mitochondria
5. Lysosomes6. Peroxisomes
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Plasma membrane
sER
rER
Mitochondrion
Lysosome
Golgi
apparatus
4. Mitochondria
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Rod-shaped or rounded with double membrane
Inner membrane : folded shelves (cristae)
: studded with enzymes
Outer membrane : smooth
4. Mitochondria
Outermembrane
Innermembrane(cristae)
enzymes
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Rod-shaped or rounded with double membrane
Inner membrane : folded shelves (cristae)
: studded with enzymes
Outer membrane : smooth
4. Mitochondria
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Mitochondria, in large numbers, produce cytoplasmic
acidophilia (due to large amount of membrane they contain)
Mitochondria contain theirown DNA for protein synthesis
and replication independent of the cell nucleus.
Functions:
Formation of ATP (generate energy)
Synthesis of lipid
4. Mitochondria
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Found in which cells?
Cells that produce/spend large amount of energy
All cells except red blood cells, terminal keratinocytes
Found in which part of cell?
striated muscle cells
middle piece of spermatozoa proximal convoluted renal tubule cells
Region where energy usage is intense e.g.
apex of ciliated cells mid-piece of spermatozoa base of proximal convoluted renal tubule cells
4. Mitochondria
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MEMBRANOUS ORGANELLES
1. Plasma/cell membrane
2. Endoplasmic reticulum
a. Smooth ERb. Rough ER
3. Golgi apparatus
4. Mitochondria
5. Lysosomes6. Peroxisomes
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Plasma membrane
sER
rER
Mitochondrion
Lysosome
Golgi
apparatus
5. Lysosome
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Lysosomes (L) seen as dark stained
cytoplasmic granules in renal tubular
cells
L = Lysosome; N = Nucleus
Lumen of renal tubule seen as
a long slit
5. Lysosome
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EM showing 4 dark secondary lysosomes surrounded by mitochondria
5. Lysosome
Lysosomes
Mitochondria
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Digestive organelles, rounded in shape.
Functions:
Numerous in cells with phagocytic activity
(e.g. macrophages, neutrophil leucocytes,
renal tubular cells)
Intracellular digestion Recycling of cellular components
Lysosomal enzymes inactive at cytosol pH (~7.2)
(this prevents leakage of enzymes)
Contains hydrolytic enzymes
(e.g. protease, lipase, ribonuclease, acid phosphatase)
5. Lysosome
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Acid Vesicle System
Primary lysosomes
Lysosomes newly formed
from Golgi cisternae.
Secondary lysosomes
Primary lysosomes that
contains the material to be
digested.
Residual bodies(Tertiary lysosomes)
Vacuoles filled with hydrolytic
breakdown contents of
secondary lysosomes.
5. Lysosome
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MEMBRANOUS ORGANELLES
1. Plasma/cell membrane
2. Endoplasmic reticulum
a. Smooth ERb. Rough ER
3. Golgi apparatus
4. Mitochondria
5. Lysosomes6. Peroxisomes
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6. Peroxisomes (Microbodies)
Peroxisomes seen as small membrane-bound, spherical bodies (arrows)
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Spherical membranous structures containing oxidative
enzymes (peroxidases, catalases)
6. Peroxisomes (Microbodies)
Numerous in liver and kidney cells.
Functions:
Detoxify noxious agents
Kill microorganismsPeroxidases
Regulate H2O2 content of cells Catalases
F oxidation of fatty acids
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Membranous
1. Plasma/cell membrane
2. Endoplasmic reticulum
a. Smooth ER
b. Rough ER
3. Golgi apparatus
4. Mitochondria
5. Lysosomes
6. Peroxisomes
CYTOPLASM
Non-membranous
1. Microtubule
2. Microfilaments
3. Centrioles
4. Ribosomes
Organelles
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NON-MEMBRANOUS ORGANELLES
1. Microtubules
2. Microfilaments
3. Centrioles
4. Ribosomes
Functions:
C
ytoskeleton
Maintains cell shape
Movement oforganelles or entire cell
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13
Basic subunits of protofilaments are
known as Tubulindimers/molecules
Each tubulin dimer is composed of
E-tubulin and F-tubulin molecules
EFTubulin
dimer
Protofilament Nonbranching hollow cylinders
(20-25 nm in diameter; 5nm thick)
Composed of 13 circularly arranged
globular protein subunits - protofilaments
Structure
1. Microtubules
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arrows = microtubules, LS arrows = microtubules, TS
1. Microtubules
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Provide rigidity of cell.
Functions:
Regulate movement of chromosomes.
(during mitosis and meiosis)
Regulate movement of organelles and vesicles.
Provide motion of cilia and flagella.
Maintain shape of cell.
1. Microtubules
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Axoneme of cilia and flagella (A)
Basal bodies of cilia (B) Centrioles (C)
Mitotic spindle fibers (M)
Microtubules are present in all cellsexceptred blood cells
AA
BB
CC
MM
Microtubules are found in the following regions of cells:
1. Microtubules
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NON-MEMBRANOUS ORGANELLES
1. Microtubules
2. Microfilaments
3. Centrioles
4. Ribosomes
Functions:
Cytoskeleton
Maintains cell shape
Movement oforganelles or entire cell
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Actin filaments are thin filaments that interact with
myosin to produce intracellular or cellular movement
Actin microfilaments are found in all cell types
Muscle cell contains 2 types of microfilaments -
actin and myosin
2. Microfilaments (Thin filaments)
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2. Microfilaments (Thin filaments)
AF = Actin (thin) filaments; M = Microtubules
EM of fibroblast cytoplasm showing actin filaments and microtubules
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Anchorage and movement of membrane proteins.
Functions:
Formation of structural core of microvilli.
Movement of plasma membrane
(e.g. endocytosis, exocytosis, cytokinesis)
Locomotion of cells.
Extension of cell processes.
2. Microfilaments (Thin filaments)
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Intermediate Filaments
8-10 nm
Fibroussubunit
In addition to thin (actin) and thick (myosin) filaments,cells contain another class of intermediate-sized filaments
(10-12 nm diameter).
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Type ofIntermediate Filament Location
Cytokeratins (Keratins) Epithelial cells
Desmin Muscles (smooth and striated)
Glial Fibrillary Acidic Protein Astrocytes
Neurofilament protein Neurons (soma and processes)
Nuclear lamin Nucleus of all cells
Vimentin Mesenchymal cells
Intermediate Filaments
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Intermediate Filaments
Intermediate filaments in skin epithelial cell
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Provide structural framework/support for cell.
Functions:
Anchor the nucleus in place.
Provide structural framework of nuclear membrane.
Provide connection between cell membrane and
cytoskeleton
Intermediate Filaments
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Intermediate Filaments
Clinical Application
Antigens
Type ofIntermediate FilamentDiagnosis
Cytokeratins (Keratins)
Tumors of epithelial origin Desmin Tumors of muscles
Glial Fibrillary Acidic Protein Tumors of glial cells
Vimentin Tumors of connective tissue
Identification of specific type of intermediate filamentin tumors can reveal the origin of tumor.This information is important for diagnosis and treatment.
Identification of intermediate filament proteins is done
by immunocytochemical methods.
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NON-MEMBRANOUS ORGANELLES
1. Microtubules
2. Microfilaments
3. Centrioles
4. Ribosomes
Functions:
Cytoskeleton
Maintains cell shape
Movement oforganelles or entire cell
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Each centriole is composed of 9 microtubule triplets
(linked by proteins)
3. Centrioles
Centrioles exist in pairs, arranged at right-angles to
each other.
Located near the nucleus of non-dividing cells
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Functions:
Organises formation ofmitotic spindle in both normal
and dividing (mitotic) cells.
Organises development of specialised microtubulesin motile cilia.
3. Centrioles
Centrosome
This region contains a pair of centrioles.
It is the site from which microtubules originate.
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NON-MEMBRANOUS ORGANELLES
1. Microtubules
2. Microfilaments
3. Centrioles
4. Ribosomes
Functions:
Cytoskeleton
Maintains cell shape
Movement oforganelles or entire cell
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Composed of rRNA and proteins.
4. Ribosomes
Found as free form or membrane-bound.
Synthesize protein.
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Polysomes
are groups of ribosomes attached to a thread of
messenger RNA (mRNA)
Cytoplasmic basophilia
is due to the presence of numerous rRNA.
4. Ribosomes
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Functions
Types ofRibosome ProteinsSynthesized
Polysomes Proteins exported from cell.
Integral proteins of plasma membrane
Free ribosomes Proteins within cell (cytoplasmic
elements)
4. Ribosomes
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Primary componentsinvolved in protein synthesis
Ribosomes/polysomes
Golgi apparatus
Rough endoplasmic
reticulum (rER)
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Cytoplasmic matrix
Organelles Inclusions
CYTOPLASM
I l i
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Non-living components of the cell.
Inclusions
No metabolic activity.
Components ofInclusions
Membrane-bound Without membrane
Secretory granules
e.g. zymogen granules
Lipid deposits
(storage form of triglycerides)
Pigment deposits
e.g. Hb, melanin, lipofuscin
Glycogen deposits
(storage form of glucose)
I l i
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Inclusions
Secretory granules
Secretory granules seen in
association with Golgi complex and
vacuoles
C = Vacuoles; G = Golgi complex;
S = Secretory granules
G
CS
S
S
S
I l i
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Inclusions
Pigment deposits
Liver cells with pigment deposits
(Giemsa stain)
H = Hepatocyte; M = Macrophage;
PD = Pigment deposit
I l i
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Inclusions
Lipid deposits
L = Lipid droplets;
M = mitochondria (anomalous)
Lipid droplets appear as vacuoles
in the cytoplasm (underLM)
(as lipid was extracted by solvents
during tissue processing)
Lipid droplets as seen under EM
in adrenal gland
I l i
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Inclusions
Glycogen deposits
G = glycogen granules;
m = mitochondria; N = nucleus
appear as:
emptyregions underLM
(as they were lost during
routine tissue processing)
rosette-shapedgranules
underEM
found in large amounts in liver
and striated muscle cells
I l i
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Inclusions
Glycogen deposits
G = glycogen granules;
m = mitochondria
appear as:
emptyregions underLM
(as they were lost during
routine tissue processing)
rosette-shapedgranules
underEM
found in large amounts in liver
and striated muscle cells
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Cell
Nucleus
Cytoplasmic matrix
Organelles
Inclusions
Cytoplasm
Nuclear envelope
Nucleoplasm Nucleolus
Chromatin
Cell is the basic structural and functional unit
of all multicellular organisms
THE NUCLEUS
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THE NUCLEUS
Size Largest organelle of the cell
Shape Spherical
Spindle to oblong
Disk-shaped
Twisted
Lobulated
Number Single
Multiple (skeletal muscle, osteoclast)
Absent (mature RBC)
Position Central
Peripheral (skeletal muscle)
S th M l C ll N l i
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Oval shape
Single nucleus per cell
Central in position
Smooth Muscle Cell NucleiCharacteristic Features
Skeletal M scle Cell N clei
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Skeletal Muscle Cell NucleiCharacteristic Features
Flattened nuclei
More than one nucleus per cell
Peripheral in position
Skeletal Muscle Cell Nuclei
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Skeletal Muscle Cell NucleiCharacteristic Features
Flattened nuclei
More than one nucleus per cell
Peripheral in position
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The Nucleus
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The Nucleus
Outer nuclearmembrane
rER
ribosomes
Inner nuclearmembrane
Nuclear pore
nu
np
ch
Chromatin (ch)
DNA inside the nucleus inthe form of coiled strands.
Visible as chromosomes
during cell division.
Heterochromatin
Visible under LM ascondensed basophilic clumps.
At the periphery of nucleus.
Inactive form of chromatin.
Euchromatin Not visible as well defined
structure under LM.
Scattered throughout nucleus.
Active form of chromatin.
The Nucleus
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hetero-chromatin
euchromatin
nucleolus
Chromatin (ch)
DNA inside the nucleus inthe form of coiled strands.
Visible as chromosomes
during cell division.
Heterochromatin
Visible under LM ascondensed basophilic clumps.
At the periphery of nucleus.
Inactive form of chromatin.
Euchromatin Not visible as well defined
structure under LM.
Scattered throughout nucleus.
Active form of chromatin.
The Nucleus
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heterochromatinheterochromatin
euchromatineuchromatin
nucleolusnucleolus
Chromatin (ch)
DNA inside the nucleus inthe form of coiled strands.
Visible as chromosomes
during cell division.
Heterochromatin
Visible under LM ascondensed basophilic clumps.
At the periphery of nucleus.
Inactive form of chromatin.
Euchromatin Not visible as well defined
structure under LM.
Scattered throughout nucleus.
Active form of chromatin.
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What is the difference between organelle and
inclusion?
Review questions
Name:
4 membranous organelles
4 non-membranous organelles
Name 2 modifications of plasma membrane
stating the function of each.
Is the plasma membrane visible or not?
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For each organelle, state one function and one
location (cell) where it is found in abundance,.
State 2 main functions of cytoskeleton.
Name the largest organelle.
State the differences between euchromatin and
heterochromatin.
Review questions
Name 4 inclusions and state the content of each.
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END OF THE CELLEND OF THE CELL