Download Lecture 1 The Nucleus

Objectives
The Nucleus
form and information
Tom Hartman
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Detecting the nucleus.
Observing the nucleus.
Ultrastructure of the nucleus.
Properties of the nucleus.
Physical components of the nucleus.
Activities of the nucleus.
Cell theory
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Robert Hooke was the first person to observe cells in 1665.
– He observed thin slices of cork under a simple microscope.
– He saw tiny empty compartments that he called cells after the
‘bedrooms’ in monasteries.
– He noted that other plant cells contain ‘juices’.
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In 1820 Robert Brown observed a sphere-like structure in every
cell. He named it the nucleus.
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In 1855 Rudolf Virchow stated that new cells arise from the
division of pre-existing cells and that chemical reactions needed
for life occurred inside the cell.
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In 1883 Mathias Schleiden and Theodor Schwann proposed that
all plants and animals were composed of cells.
Cell theory
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All organisms are composed of one or more
cells.
2.
The cell is the basic, living unit of organisation.
3.
Cells arise from pre-existing cells.
4.
Each cell maintains itself within optimal
parameters: homeostasis.
The study of cells is called cytology.
What has a nucleus?
• No nucleus is found in:
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Bacteria
Viruses
Prions
Some specialised cells
• Possession of a nucleus defines a
domain of life: the eukaryotes.
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Why prokaryotes are relevant to
crime scenes.
Life
• Bacteria
Bacteria
Eukaryotes
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Vast populations and species.
Vital component of our bodies.
Decomposition and disease.
Component of cells (mitochondria).
• With own specific genome.
• Allows for relationships to be investigated in ‘deep
time’.
Prokaryotes
• Archaebacteria
Archaebacteria
– Extremophiles with amazing biochemistry.
– Their DNA metabolism is the basis of most
DNA tests: the PCR.
Eukaryote and Prokaryote
PCR
• Polymerase Chain Reaction
– Uses an enzyme from Thermus
aquaticus (Taq).
– Specific DNA sequences can be
bulked up quickly and ‘easily’.
The size of cells
A prokaryotic cell
10 m
Human height
1m
Nucleoid: region where
the cell’s DNA is located (not
enclosed by a membrane)
0.1 m
Chicken egg
1 cm
Ribosomes: organelles that
synthesize proteins
Frog egg
100 µm
Most plant and
animal cells
Capsule: jelly-like outer coating
of many prokaryotes
10 µm
0.5 µm
Flagella: locomotion
organelles of
some bacteria
(b) A thin section through the
bacterium Bacillus coagulans
(TEM)
1 µm
100 nm
nucleus
Nucleus
Most bacteria
Most bacteria
Mitochondrion
Smallest bacteria
Viruses
Ribosomes
10 nm
Electron m icroscope
Cell wall: rigid structure outside
the plasma membrane
Light m icroscope
1 mm
Plasma membrane: membrane
enclosing the cytoplasm
(a) A typical
rod-shaped bacterium
Length of some
nerve and
muscle cells
Unaided eye
Pili: attachment structures on
the surface of some prokaryotes
Proteins
Lipids
1 nm
0.1 nm
Small molecules
Atoms
Measurements
1 centimeter (cm) = 10−2 meter (m) = 0.4 inch
1 millimeter (mm) = 10–3 m
1 micrometer (µm) = 10–3 mm = 10−6 m
1 nanometer (nm) = 10–3 µm = 10− 9 m
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Light Microscopy
Double membrane
TECHNIQUE
RESULTS
(a) Brightfield (unstained specimen).
50 µm
(b) Brightfield (stained specimen).
(c) Phase-contrast.
A cell seen with fluorescence
(d) Differential-interference-contrast (Nomarski).
(e) Fluorescence.
50 µm
(f) Confocal.
10 µm
50 µm
Electron Microscopy
TECHNIQUE
(a) Scanning electron microscopy (SEM).
RESULTS
Cilia
1 µm
Cell Fractionation
APPLICTION Cell fractionation is used to isolate
(fractionate) cell components, based on size and density.
Longitudinal
section of
cilium
Cross section
of cilium
1 µm
TECHNIQUE
First, cells are homogenized in a blender to
break them up. The resulting mixture (cell homogenate) is then
centrifuged at various speeds and durations to fractionate the cell
components, forming a series of pellets.
(b) Transmission electron microscopy (TEM).
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Hom ogenization
Tissue
cells
1000 g
Homogenate
(1000 times the
force of gravity)
Differential centrifugation
10 min
Supernatant poured
into next tube
20,000 g
20 min
Pellet rich in
nuclei and
cellular debris
80,000 g
60 min
RESULTS
In the original experiments, the researchers
used microscopy to identify the organelles in each pellet,
establishing a baseline for further experiments. In the next series of
experiments, researchers used biochemical methods to determine
the metabolic functions associated with each type of organelle.
Researchers currently use cell fractionation to isolate particular
organelles in order to study further details of their function.
150,000 g
3 hr
Pellet rich in
mitochondria
(and chloroplasts if cells
are from a Pellet rich in
plant)
“microsomes”
(pieces of
plasma membranes and
Pellet rich in
cells’ internal ribosomes
membranes)
Somatic Cells
• Somatic cells (soma = body):
– all body cells except sex cells
Sex Cells
• Sex cells (germ cells):
– reproductive cells
– male sperm
– female oocytes (eggs)
The Cell
• Performs all life functions
The nucleus within the cell
Figure 3–1
From Martini
‘Fundamentals of
Anatomy and
Physiology’
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Animal Cell
Nuclear envelope
ENDOPLASMIC RETICULUM (ER)
Rough ER
The Nucleus
NUCLEUS
Nucleolus
Smooth ER
Chromatin
Flagelium
Plasma membrane
Centrosome
• Is the cell’s control center
CYTOSKELETON
Microfilaments
Intermediate filaments
Ribosomes
Microtubules
Microvilli
Golgi apparatus
Peroxisome
Mitochondrion
Lysosome
In animal cells but not plant cells:
Lysosomes
Centrioles
Flagella (in some plant sperm)
From Campbell and Reece ‘Biology’
Figure 3–10a
Structure of the Nucleus
• Nucleus:
– largest organelle
• Nuclear envelope:
– double membrane around the nucleus
• Perinuclear space:
– between 2 layers of nuclear envelope
• Nuclear pores:
– communication passages
Nucleoli in Nucleus
Within the Nucleus
• DNA:
– all information to build and run organisms
– kept in various levels of condensation
• Nucleoplasm:
– fluid containing ions, enzymes, nucleotides,
and some RNA
• Nuclear matrix:
– support filaments
The nucleus and its envelope
Nucleus
Nucleus
1 µm
• Are related to protein production
• Are made of RNA, enzymes, and
histones
• Synthesize rRNA and ribosomal
subunits
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Rough ER
Surface of nuclear enve lope.
TEM of a specimen prepared by
a special technique known as
freeze-fracture.
0.25 µm
Ribosome
1 µm
Close-up of nuclear
envelope
Pore complexes (TEM). Each pore is ringed
by protein particles.
Nuclear lamina (TEM). The netlike lamina
lines the inner surface of the nuclear envelope.
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The nucleus and its envelope
The nucleus and its envelope
Nucleus
Nucleus
Nucleus
1 µm
Nucleus
1 µm
Nucleolus
Nucleolus
Chromatin
Chromatin
Nuclear envelope:
Inner membrane
Nuclear envelope:
Inner membrane
Outer membrane
Outer membrane
Nuclear pore
Nuclear pore
Pore
complex
Pore
complex
Rough ER
Surface of nuclear enve lope.
TEM of a specimen prepared by
a special technique known as
freeze-fracture.
0.25 µm
Ribosome
Rough ER
Surface of nuclear enve lope.
TEM of a specimen prepared by
a special technique known as
freeze-fracture.
0.25 µm
1 µm
Ribosome
Close-up of nuclear
envelope
Pore complexes (TEM). Each pore is ringed
by protein particles.
Nuclear lamina (TEM). The netlike lamina
lines the inner surface of the nuclear envelope.
Pore complexes (TEM). Each pore is ringed
by protein particles.
The nucleus and its envelope
Nuclear lamina (TEM). The netlike lamina
lines the inner surface of the nuclear envelope.
The nucleus is not in
isolation.
Nucleus
Nucleus
1 µm
1 µm
Close-up of nuclear
envelope
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Rough ER
Surface of nuclear enve lope.
TEM of a specimen prepared by
a special technique known as
freeze-fracture.
0.25 µm
Ribosome
1 µm
Close-up of nuclear
envelope
Pore complexes (TEM). Each pore is ringed
by protein particles.
Nuclear lamina (TEM). The netlike lamina
lines the inner surface of the nuclear envelope.
Ribosomes
Ribosomes
ER
Ribosomes
Ribosomes
Cytosol
ER
Cytosol
Endoplasmic reticulum (ER)
Endoplasmic reticulum (ER)
Free ribosomes
Free ribosomes
Bound ribosomes
Bound ribosomes
Large
subunit
0.5 µm
TEM showing ER and ribosomes
Small
subunit
Diagram of a ribosome
Large
subunit
0.5 µm
TEM showing ER and ribosomes
Small
subunit
Diagram of a ribosome
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Endoplasmic reticulum (ER)
Smooth ER
Rough ER
• endo = within, plasm = cytoplasm,
reticulum = network
• Cisternae are storage chambers
within membranes
Nuclear
envelope
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
Endoplasmic Reticulum
(ER)
Transitional ER
Rough ER
200 µm
Relationships among organelles of the
endomembrane system
1 Nuclear envelope is
connected to rough ER,
which is also continuous
with smooth ER
Nucleus
Relationships among organelles of the
endomembrane system
1 Nuclear envelope is
connected to rough ER,
which is also continuous
with smooth ER
Nucleus
Rough ER
Rough ER
2 Membranes and proteins
produced by the ER flow in
the form of transport vesicles
to the Golgi
Smooth ER
Smooth ER
cis Golgi
Nuclear envelope
Nuclear envelope
Transport
vesicle
3 Golgi pinches off transport
vesicles and other vesicles that
give rise to lysosomes and
vacuoles
3
trans Golgi
4 Lysosome available 5 Transport vesicle carries
for fusion with another proteins to plasma
vesicle for digestion
membrane for secretion
Relationships among organelles of the
endomembrane system
Centrosome containing a pair of centrioles
Centrosome
1 Nuclear envelope is
connected to rough ER,
which is also continuous
with smooth ER
Nucleus
Rough ER
Microtubule
2 Membranes and proteins
produced by the ER flow in
the form of transport vesicles
to the Golgi
Centrioles
Smooth ER
cis Golgi
Nuclear envelope
0.25 µm
Transport
vesicle
33 Golgi pinches off transport
vesicles and other vesicles that
give rise to lysosomes and
vacuoles
trans Golgi
Plasma
membrane
4 Lysosome available 5 Transport vesicle carries 6 Plasma membrane expands
for fusion with another proteins to plasma
by fusion of vesicles; proteins
vesicle for digestion
membrane for secretion
are secreted from cell
Longitudinal section
of one centriole
Microtubules Cross section
of the other centriole
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Nucleus summary 1
Nucleus summary 2
STRUCTURE
FUNCTION
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Largest organelle in the cell (size depends on species DNA
amount).
Surrounded by a nuclear membrane / envelope /
mucleolemma
– Double membrane – outer is continuous with the ER
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Nuclear pores in the membrane allow the passage of large
molecules in & out (e.g. messengerRNA)
The contents of the nucleus is called nucleoplasm – this
contains chromatin which makes up the DNA of the cell –
in non-dividing cells it is spread out and during cell division
it condenses to form the chromosomes
Contains the structure called the nucleolus is found in the
nucleus.
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Acts as the control centre of the cell through the
production of mRNA and protein synthesis
Retains the genetic material in the cell in the form of DNA /
chromosomes
Nucleolus responsible for the manufacture of ribosomal
RNA (rRNA) & ribosomes
Central role in the process of cell division
Nuclei in the news
• Cells taken from a sixsixyearyear-old Finnish Dorset
ewe and cultured in a
lab.
• 277 cells then fused with
277 unfertilized eggs
(each with the nucleus
removed).
• 29 viable reconstructed
eggs survived and were
implanted in surrogate
Blackface ewes.
• 1 gave birth to Dolly.
Dolly
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