Teaching Plan of Cell Biology
Chapter 9 Nucleus
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
Lesson plans
roll number：_______9________
Course Title
Medical Cell
Biology
Major
clinic
Class
Teacher
Xiamixinuer.Yilike
Plan hours
8 hours
Professional
level
Professional
Title
Name of the
Lecture
Biology Professor
The time of
writing
Chapter 9: The Cell Nucleus
Using time
undergradu
ate course
Teaching Purposes: To learn ultrastructure and basic functions of nucleus.
Teaching
Purposes
and
Requiremen
t
Teaching Requirements:
1. Mastering: ultrastructure of nuclear envelope; nuclear pore complex;
composition and four levels organization of chromatin; packaging of chromatin;
types of chromatin.
2. Comprehending: structure and function of nucleolus; function of nuclear pore
complex; process of RNA processing.
3
U d t di b i f
ti
f
l
l
ti
Important Important points ：ultrastructure of nuclear envelope,nucleolus,chromatin and
and Difficult chromosome
Difficult points: structure and function of nucleolus. Condensed model of
points
chromatin
Update
teaching increase a case.
content
Teaching Teaching methods ：Multimedia lectures given . Heuristic teaching methods will
methods be used.
and
organizational arrangements ：ultrastructure of nuclear envelope3 hours,four
organization
levels organization of chromatin; packaging of chromatin; types of chromatin.2
al
hours,chromosome and nucleolus will be teach 2 hours,
arrangemen
Teaching multiedia will be used.
tools
text book ：Cell Biology , China Medical University（6th edition）
Textbook
Reference ：1.Essential Cell Biology.Bruce Albert’s；2.Cell and Molecular
and
reference Biology，Gerald Karp；3. Molecular Biology Disc；4. Lysosomes in biology
and pathology J. T. Dingle5.The cytoskeleton: an introductory survey/
books
Q28/C74,M. Schliwa;6.Essentials of cell biology/2d ed. Q28/C71=2,Dyson,
collective
preparation Mainly Teach the ultrastructures of nucleus.
of
instruction
Opinion of Agreed to carry out prepared the lessons plan. Give attention to use appopirate
the
signature of the
teaching methods .
department dean：
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
Test for Cytoskeleton system
（Print the sheet alone and let students finish it before the class in 10min）
Roll No
Name
1.
.
Marks________
is a complex network of interconnected 3types of filaments that extends
throughout the cytosol.
2.
MTs assemble from
which include centrosome, centromere and basal
bodies of cilia and flagella.
are the protein building blocks of MFs
are the most abundant and stable components of the cytoskeleton.
5.
binding to tubulin dimers, prevent MTs polymerization.
6.
binding to MTs, stabilize MTs.
7.
can cause cytosolic MTs deploy.
8.
The formula of Mt formation of basal of cilia and flagella is
9.
Actin filaments are destabilized by
10. A singlet microtubule has
.
protofilaments.
11. Kinesins are motor proteins that move in
direction(s) along
.
12. Which group of proteins are motor proteins that interact with microtubules?
13. The functions of Microtubules are
,
14. The functions of Microfilaments are
and
,
,
, and
,
.
,
,
.
15. The three types of protein filaments that form the cytoskeleton,they are ,
16. Tubulin formed by and two kinds of monosomic forms.
17. A triplet microtubule has
and
protofilaments.
18. . Muscle thin filaments are composed of
19.
20.
are abundant in the human respiratory tract.
have a plus and minus ends.
21. The functions of cytoskeleton system are
Biology Department of Xinjiang Medical University
,
,
,and
.
Teaching Plan of Cell Biology
22.
protofilaments exist in cilia and flagella
23. .
protofilaments exist in centrioles and basal bodies
24. MTOC include
,
, and
.
25. Compare the structure, diameter, protein subunit among three types of
cytoskeleton.
Property
Microtubules
Microfilaments
Intermediate Filaments
Structure
Diameter
Protein
Subunit
Teaching Purposes: To learn ultrastructure and basic functions of nucleus.
Teaching Requirements:
1. Mastering: ultrastructure of nuclear envelop; nuclear pore complex; composition and
four levels organization of chromatin; packaging of chromatin; types of chromatin.
2. Comprehending: structure and function of nucleolus; function of nuclear pore complex;
process of RNA processing.
3. Understanding: basic function of nucleus; nuclear matrix.
Textbook
<Cell Biology> Abridgen by department of Cell Biology China Medical
University,sixth edition,2000.
Reference
(1) Arberts, B. et al. Molecular Biology of the Cell, Garland Publishing, Inc.
2002, 2004, 2008.
(2) Arberts, B. et al. Essential Cell Biology, An Introduction to the Molecular
Biology of the cell, Garland Publishing, Inc. 1997, 2004.
(3) Karp, G. Cell and Molecular Biology--Concepts and Experiments, John &
Whley Sons, Inc. 2002, 2005, 2007.
(4) Lodish H. et al. Molecular Cell Biology, W.H.Freeman, Inc. 1999, 2007.
(5) Becker W.M. The World of the Cell, The Benjamin/Cummings Publishing
Company. 2000 .
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
(6) Kleinsmith L.J and Kish V.M. Principles of Cell and Molecular Biology,
Harper Collins College Publishers. 1995.
Teaching Outline
1. The nucleus: Nuclear envelope and NPC
(1) Structure of nuclear envelope: Double-membrane
(2) Nuclear pore complex (NPC)
(3) Molecules enter and exit the nucleus through nuclear pore complex
2. Eukaryotes package DNA in Chromatin and chromosomes
(1) Nucleosomes
(2) DNA packaging
(3) Euchromatin and Heterochromatin
3. The number, size and shape of Chromosome
4. Nucleolus
(1) Structure
(2) Functions of nucleolus: Ribosomal Biogenesis
attention： master point※※※；comprehending point※※；understand※
Nucleus
Double-membrane nuclear envelope surrounds the tipical
interphase nucleus.
The main functions of nucleus are: a. Carry genetic
information（DNA）;b.Duplicate,transcript of genetic
information and control protein synthesis;c.Regulation and control centre of living
action of cells. NP(nucleoplasmic index):NP= Vn/(Vc－Vn), n for nucleus, c for
cell.Usually size of nucleus can be estimated by calculate the NP.Normal cell
NP≈0.5，Dividing cell NP>0.5，Aging cell NP<0.5
A typical nonmitotic nucleus includes four major components.see pictures below:
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
A.Nuclear envelope：As shown in the picture right
side nuclear envelope consists of two membranes by a
perinuclear space. Outer nuclear membrane connact with
the lumen of RER. And outer surface attached by
ribosomes. Inner nuclear membrane no attached by
ribosomes but it contains specific proteins that act as
binding sites for the nuclear lamina. The nuclear lamina
supports the nuclear envelope: Gives shape and stability of
nuclear envelope; Provides a
structure link between chromatin and
nuclear Envelope;The nuclear lamina
is composed of lamins.The integrity
of the nuclear lamina is regulated by
phosphorylation
and
dephosphorylation.
(see
left )Perinuclearspace:Includes variety of enzymes and protein.
picture
The structure of Nuclear pore complex (NPC) Old model:Ring subunit：8
pair,Annular subunit：8,Central plug：1and these connect with fibril,as seen in
below picture.
The functions of NPC are molecules enter and exit the nucleus through nuclear pore
complex by passive transport and active transport.There are 3000-4000
NPC/cell(mammalian); To import about 106 histone/3 mins.(DNA-sythesizing cell) =
100 histone/ min/NPC.Each NPC contains one or more open aqueous channels: 9 nm
in diameter and 15 nm long <10 nm in diameter, <60kd globular protein Able to enter
the nucleus.The effective size of these channels has been determined by injecting
various sizes of colloidal gold particles and examined by electron microscopy.see
picture
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
Transport of large proteins into nucleus needs nuclear localization signal
(NLS)
Pore diameter is about 9nm but much larger objects, including ribosomal subunits can
pass through (albeit slower than smaller molecules). This implies that recognition of
appropriate signal allows temporary stretching of the pore.Energy is required.
B.Chromatin and chromosome
Chromatin:Eukaryotes package DNA in Chromatin and chromosomes;Each human
cell contains about 2 m of DNA within nucleus if stretched end-to-end, yet the
nucleus of a human cell itself is only about 6 μm in diameter. Compaction
ratio=nearly 10000-fold. (Chromosome 22: DNA 1.5cmÆ2 μ m); Chromosomes
exist in different states throughout the life of a cell.it’s a threadlike thing fibers, Exist
in interphase nucleus 10-30nm in diameter,dispersed through the nucleus. Chromatin
can be stained by basic/alkaline dye, it is genetic material. DNA+Proteins+nonProteins+RNA. histone is rich in arginine or lysine, so it is positive at neutral PH, you
know DNA is negative, thus, histone can be attached to DNA tightly and protects the
long and thin DNA molecule. Each chromatin contains one DNA molecule.
The types of chromatin: 1 Euchromatin:containing functional genes, out stretched
or relaxed at interphase; condensed and darkly stained at metaphase. Stained lightly,
locate in the center of inlerphase nucleus. It’s about 10 nm thick in diameter, it can
transcript actively. We also call it active chromatin.
2. Heterochromatin: Heterochromatin is more condensed than euchrom atin. Stained
deeply. It's about 20-30nm in diameter. Usually they exist around the nucleolus or
inside the inner nuclear envelope. Heterochromatin transcript inactively, so called
inactive chromatin. It can be subdivided into two types again.①.Constitutive
heterochromatin: it is condensed all the time in all of cell types. ②Facultative
heterochromatin: it is just condensed in some cells at some time.
The folding level of chromatin:The popular multiple coiling model: Scaffold radial
loop structure model
(1)The first and most fundamental packing level of chromatin is nucleosome.
Nucleosomes are packed together to form chromatin fibers and
chromosomes .Nonhistone proteins provide a structural scaffold for long chromatin
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
loops. 2nm DNA –11nm nucleosome – 30nm fiber – Loop– Metaphase chromosome
First degree:Nucleosomes ;Second degree: Filament 10nm in diameter ; Third level:
Fiber,30nm in diameter and Fourth level: Chromosome.
a. DNA packaging:First degree of packaging is Nucleosomes.
Nucleosomes are the basic unit of chromatin structure. Evidence: (1)Electron
micrographs of chromatin fibers
Isolated from interphase nucleus: 30nm thick Chromatin unpacked, show the
nuclesome
Evidence: (3)X-ray diffraction
studies A histone octamer forms the
nucleosome core:
Nucleosome is the first basic unit of
chromatin structure, which consists of
DNA and five different kinds of histone, that
is H2A, H2B, H3, H4 and H 1, and the DNA is
about
200 base pairs long.Nucleosome includes a core
histone and a linker DNA ,about 54 base pairs. The core histone contains a histone
octamer and a winding DNA, the histone octamer consists of four pairs of each
histone, that is H2A, H2B, H3 and H4 .so called histone octamer. it contains a
tetramer in the center and two dimers attached to the tetramer at both sides, the
tetramer includes a couple of H3 and H4 ,each dimer includes a H2A, H2B .
Outside of it, DNA winds around it in the left- handed helical form about 1.75 circles;
the DNA is of about 146 base pairs long. Histone H1 lies near the point where DNA
enters and exits the nucleosome core histone, it may maintain or keep the chromatin's
nucleosome structure.In a word, after this first packing, the DNA in chromatin is
condensed about 6-7 times in length
The second packing level of chromatin: solenoid 30-nm-diameter chromatin thread
is the second packing structure of chromatin, called solenoid, using electron
microscope and x-ray diffraction analysis, people find that:Each six nucleosomes
form a helical line tube or loop domain .To form the solenoid need a histone H1 at
each end of loop domain, In principle, histone H1 can establish and maintain the loop
domain in chromatin. Meanwhile clamp or contact neighboring loop domains together
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
and form solenoid. The inside diameter of solenoid is about 11nm, and the outside
diameter is 30 nm.After the second folding, the length of DNA is further condensed 6
times,
The third packing structure of chromatin:Is supersolenoid.after further folding,
solenoid form the third folding level ---supersolenoid. it’s about 300-400nm diameter
and 11-60 nm long, the DNA is condensed by 40 times.
The fourth folding structure: chromatid:Finally supersolenoid is folded again, and
become the most condensed structure of chromatin. We call it chromosome, this is the
fourth folding structure. In fact, it’s chromatid.
As a result, after packing four times, the DNA is condensed nearly 10000 times
(7×6×40×5 is equal to 8400), a 5cm length of DNA become a 5ìm long chromosome.
The 5μm chromosome is very easy to package into the nucleus.
Chromosome:
Chromosome number, size, and shape at metaphase are species specific.
Chromosomes: (M phase): Typical chromosome is a metaphase chromosome at a cell
division; these fibers condense and fold into larger, compact structure.
Chromosome In general, the length of chromosome is from 2-10 ìm long, thus after
this folding, the DNA is condensed about 5 times in length. a typical chromosome
is at the melaphase of Mitosis.
Main structures of chromosome: Including centromere, arm (p and
q), secondary constriction, telomere and satellite.
1. Centromere: Each DNA molecule That
Forms a chromosome must contain a
centromere, The Centromere and Kinetochore:
serve as a site for the attachment of spindle
microtubules during mitosis and meiosis
2.Telomere:Chromosome
must
contain
two
telomeres.Telomerase is found in germ cells, not in
somatic cells.
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
The telomere length of adult is shorter than that of younger.
Telomere shortening is thought to activate a suicide program. So, telomere shortening
plays a key role in protecting the body from cancer. 90% of human tumors contain an
active telomerase.
Three functional elements are required for replication and stable inheritance of
chromosome as below picture:
Functions: a. Protect the
chromosomes from nuclease
influence; b. for the complete
replication of chromosome and c.
Prevent the ends of chromosomes
from fusing
3. Satellite: 13,14,15,21 and 22
chromosome end attached with
round structure like satellite
composes of heterochromatin .
4. Secondary constriction:1, 9, 16 chromosome always appeared narrowed part an
long arm of chromosome, compare with main constriction named secondary
constriction
5. arm (p and q) centromere divide chromosome into long and short arm ,q stand for
long arm while p stand for short arn.
Types of Chromosome according to the position of centromere :
metacentic chromosome(a),submetacentric chromosome(b)subtelocentric
chromosome(c) and telocentric chromosome(d) human haven’t the last type.
There are 46 chromosomes in a human cell.
Karyotype:Pictorial representation of full chromosomal complement arranged
according to centromere location and decreasing length.46,XX, 46,XY
Homologous chromosome, Autochromosomes, sex chromosomes
Chromosome banding:Stained or unstained constant region on chromosome length
revealed by degree of affinity for various dyes.
C.Nucleolus: Spherical shape, Visible when cell is not dividing- Contains RNA for
protein manufacture, it contains abundant proteins, about 80%. A little DNA. about 8
%. And RNA occupied up to 5-10%.
a. Structure :Nucleolus has no envelope.
Consists of: 1.Fibrillar center, 2.Dense fibrillar
component and 3.Granular component
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
Fibrillar center..a pale-staining , and rDNA genes , It includes many inactive
chromatins, which form a nucleolus organizing region.Called
NOR in brief. The main function of NOR is to tran script the ribosomal RNA or
rRNA briefly.
Dense fibrillar component:Consists of many RNA
molecules;
Granular component:The granules are the
maturing ribosomes, outside of the nucleolus the
function of nucleolus?
Synthesize rRNA and package(assembly) ribosome.
We also say that: The nucleolus is a ribosome-producing machine.
b. The function of nucleolus:
Ribosomal Biogenesis ,All the cells
ribosomes are assembled in the
nucleolus.Firstly. DNA in NOR transcript a
long 45s rRNA. it's intact. Mixed with more
than 80 kinds proteins from the cytoplasm. Then,it is
splited into 28s. 18s and 5.8s rRNA .
Small ribosomal subunits. The 18s rRNA is connected with 33 kinds of proteins, aid
form small ribosomal subunits. Which leave tile nucleus through the pore. And come
up in the cytoplasm. It's about 40s in weight finally.
large ribosomal subunit:28s 5.8s and 5s rRNA
mixed with other 49 kinds of proteins from the
cytoplasm form the large ribosomal subunit.
About 60s in weight finally. By the way 5s rRNA
come from the cytoplasm. Which subunit is
firstly appeared in the cytoplasm. Synthesis and
processing of 5s rRNA, The nucleolus disappears
during mitosis
5s rRNAs are encoded by a large number genes (Human, 2000); 5s rRNA gene
are located outside the nucleolus.5s rRNAs are transcibed by RNA poly III.The 3’
end of 5s rRNA is removed during processing.
Assembly of ribosome:
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
D.Nucleus matrix: constituted mainly by three-dimensional fiber network
structure of non-histone proteins precision except the nuclear envelope, nuclear
lamina - nuclear pore complex system, chromosome scaffold and the nucleolus
grid architecture. Including all kinds of enzymes and production such as replicon,
transcript and RNA processing and chromatin chemical component.
Summary of Cell Nucleus
(1).The components of the typical nonmitotic nucleus
(2).The components of chromatin and packaging of chromosome: Scaffold radial loop
structure model.
(3). Nucleolus components and functions.
Review:
1. Nucleolus Structure includes which parts?
2. What are the functions of nucleolus?
3. Describe briefly the difference between euchromatin and heterochromatin.
4. Describe briefly structure of nucleosome?
5. Any Questions??
6. Reference of Major Journals
7. Cell
8. Nature
9. Science
10. EMBO
Biology Department of Xinjiang Medical University
Teaching Plan of Cell Biology
11. Annual Review of Cell Biology
12. Trends in Cell Biology
13. Cell Research
14. Biology Website
15. http://www.ebiotrade.com/
16. http://www.bioon.com/
17. http://www.bbioo.com/
18. http://bbs.bioon.com/bbs/index.php
19. http://www.dxy.cn/
20. http://bbs.biooo.com/
21. NCBI-American http://www.ncbi.nlm.nih.gov
Biology Department of Xinjiang Medical University