Federal Agency of Health Protection and Social Development
Stavropol State Medical Academy
Biology with Ecology Department
Makarenko E.N.,
Boldyreva G.I.,
Parshintseva N.N.
MATERIALS FOR PRACTICAL WORKS ON
CYTOLOGY
Stavropol 2006
Федеральное Агентство по здравоохранению и социальному развитию
Ставропольская государственная медицинская академия
Кафедра биологии с экологией
Federal Agency of Health Protection and Social Development
Stavropol State Medical Academy
Biology with Ecology Department
Э.Н.Макаренко, Г.И.Болдырева, Н.Н.Паршинцева
Makarenko E.N., Boldyreva G.I., Parshintseva N.N.
МАТЕРИАЛЫ К ПРАКТИЧЕСКИМ ЗАНЯТИЯМ ПО ЦИТОЛОГИИ
Учебное пособие для студентов англоязычного отделения
MATERIALS FOR PRACTICAL WORKS ON
CYTOLOGY
Ставрополь 2006
Stavropol 2006
УДК 576.3 (07)
ББК 28.461 я 7
М 15
Материалы к практическим занятиям по цитологии. Учебное пособие для студентов
англоязычного отделения (на английском языке). – Ставрополь: Изд-во СтГМА. – 2006. – 28 с.
MATERIALS FOR PRACTICAL WORKS ON CYTOLOGY.
Textbook for students of the English –
speaking Medium. – Stavropol: StGMA. – 2006. – 28p.
Авторы: Макаренко Элина Николаевна, кандидат медицинских наук, старший преподаватель
кафедры биологии с экологией; Болдырева Галина Ивановна, старший преподаватель
кафедры биологии с экологией; Паршинцева Наталья Николаевна, старший преподаватель
кафедры иностранных языков.
Authors: senior lecturers of Biology with Ecology department Makarenko E.N.,
Boldyreva G.I.; teacher of Latin and foreign languages department of Stavropol
State Medical Academy Parshintseva N.N.
Учебное пособие включает в себя материалы основных тем курса «Цитология» для студентов
англоязычного отделения. Оно состоит из следующих разделов: Формы жизни, Сравнение
прокариотических и эукариотических клеток, Плазмалемма, Ядро, Цитоплазма, Органоиды
клетки.
This publication includes basic material of the main topics of the course of
“CYTOLOGY” for the students of the English – speaking Medium. It consists of
such topics: Forms of life, Comparison of prokaryotic and eukaryotic cells,
Plasmalemma, Nucleus, Cytoplasm, Main cell organelles.
Рецензенты: Ходжаян Анна Борисовна, доктор медицинских наук, профессор, зав. кафедрой
биологии с экологией СтГМА; Знаменская Стояна Васильевна, кандидат педагогических наук,
доцент кафедры иностранных языков с курсом латинского языка СтГМА, декан англоязычного
отделения деканата иностранных студентов.
Reviewers: Hodzhayan Anna Borisovna, professor, Doctor of Medicine, Head
of Biology with Ecology department of Stavropol State Medical Academy;
Znamenskaya Stoyana Vasilievna, dean of the English – speaking Medium.
УДК 576.3 (07)
ББК 28.461 я 7
М 15
Рекомендовано к изданию Цикловой методической комиссией Ставропольской
государственной медицинской академии по англоязычному обучению иностранных студентов.
© Stavropol State Medical
Academy.2006
INTRODUCTION
Presented textbook is intended for students of the first course of the English
– speaking Medium to preparation for practical lessons and passing an
examination in Biology. Besides topics of Cytology are important, as allow, to
study any organism at a cellular level of the organization. During the preparation
of the further doctor questions of Cytology are considered at departments of
histology, microbiology, pathological anatomy, pharmacology, etc.
The purpose of creation of the given manual is a statement in the
compressed form of the basic topics of "Biology of a cell", such as « Plasma
membrane », "Nucleus", and «Cytoplasm". The given topics are examined
under the following plan:
1) definition of concept,
2) the structural organization,
3) functional applicability.
In the manual diagrams, tables, figures, microphotos, which will help with
preparation of students, are used.
Brief Нistory
BIOLOGIA is a science that studies all living organisms. There are many
life forms existing on our planet, but all of them are divided on cellular forms
and non-cellular forms.
FORMS OF LIFE
NON-CELLULAR FORM
CELLULAR FORM
‫ ־‬Viruses
PROKARYOTES
EUKARYOTES
‫־‬
Bacteria
‫־‬
Plants
‫־‬
Cyanobacteria or
‫־‬
Animals
Green-blue alga
‫־‬
Fungi
According to a cell theory all living organisms consist of cells. Cell is the
structural and functional unit of life. Study of a cell begins with discovery of a
microscope.
Two Dutch brothers Janssen and Francis constructed the first compound
microscope in the year of 1590. In 1665 Robert Hooke reported honeycomb like
structures in a very thin slice of cork and coined the term ‘cell’ to describe them.
He published his findings in the form of a book titled ‘Micrographia’. The next
year he presented his findings to the Royal Society of London. In 1672 Marcello
Malpighi described cells as utricles. Anton Von Leeuwenhoek, for the first time,
reported the discovery of protozoans, bacteria, sperm cell and red blood
corpuscles in the year of 1674. In 1830 Purkinje coined the term protoplast to
describe the cellular substance. Robert Brown discovered a thick, rounded
structure in a cell and gave it the name of nucleus in 1831. The same year
Dujarin not only recognized the importance of cell organelles but also called
nucleus as sarcode.
The credit for proposing ‘cell theory’ goes to two German scientists,
Mathias Schleiden and Theodore Schwann. In 1838 Schleiden reported that all
the plants are made of cells only. The following year, i.e., 1839, Schwann
reported that all animals were also made of cells. Schwann also proposed that
tissues were composed of cells and the cells were the functional units of all
living organisms. Unfortunately both of them wrongly believed that cells
originated from non-living substances. Robert Remak and Rudolf Virchow
reported that cells always originated from pre-existing cells only. Our
knowledge of a cell has reached molecular level with the discovery of the
electron microscope by Knoll and Ruska in 1932.
A Comparison of Prokaryotic and Eukaryotic Cells
Type of the cells
Parts of
a cell
Structural
components
Plasmalemma
Surface
Prokaryotic
Animal
Present. Forms
invaginations, like
mesosomes et al.
Cell wall (murein)
appara-
Over membrane
tus
Eukaryotic
Sometimes capsule
(mucopolysacha-
Plant
Present
Glycocalyx
(glycolipids,
glycopeptides)
Cell wall
(cellulose)
C y t o p l a
s m
rides)
Hyaloplasm
Endoplasmatic
O
R
Present
-
Mainly granular
Mainly smooth
reticulum (ER)
Mitochondria
-
Golgi
G
Present
apparatus
Absent
Present
Forms piles of
cisternae and
vesicles
Flattened piles of
cisternae
(dictyosomes)
(GA)
A
Peroxysomes
-
Present
Present only in
higher plants
N
Lysosomes
-
E
Ribosomes
70S
Phagosomes
Autophagosomes
70S – mitochondria
80S – hyaloplasm and ER
Present. Most
plants cells lack
centrioles
Cell center
Absent
Present
Microtubules
Absent
Present
Microfilaments
Rare
Present
L
L
E
Plastids
Absent
Absent
Present
Vacuoles
Absent
Absent
Present
Cilia
Absent
Present
Absent
Present
Absent. Present in
some species
(algae)
Flagellae
S
Inclusions
Present in some
species
Proteins, lipids,
carbohydrates
(glycogen),
polyphosphates
(volutin’s granules)
Absent
Cytoskeleton
Hereditary apparatus
Nucleoid and
Proteins, lipids,
carbohydrates
(glycogen), secretory
granules, pigment et
al.
Lipids,
carbohydrates
(starch), protein
(gluten), calcium
oxalate crystals
Microtubules,
microfilaments and
microtrabecular
fibers
Occasional
microtubules
Nucleus
Plasmids
The Main Components of any Eukaryotic Cell are:
1) Plasma membrane
- Cytoplasmic membrane
- Plasmalemma
Nucleus
- Cell membrane
2) Nucleus
3) Cytoplasm
Distinction Animal from Plant Cell:
The cells of plant include
1) Cell wall (or cellulose envelope)
2) Plastids: chloroplasts, chromoplasts, and leykoplasts
3) Vacuoles,
but in animal cell these structures are absent.
Structure of Eukaryotic Animal Cell (Fig. №1)
Microvilli
С1усоgen g r a n u l e s
Pinocytic vesicle
Nuclear membrane
Plasma Membrane- Plasmalemma
Plasma membrane is the thin membrane surrounding a cell.
Thickness: 75- 100 A˚ or about 3/10 million of an inch.
Structure:
1. Composed of lipid and protein molecules.
2. Arrangement of molecules – current postulate:
a) “Sandwiched” model proposed by Davson and Danielli (1935)
The bimolecular leaflet model proposed by Davson and Danielli is an
important step in understanding of the cell membrane structure. It also
formed the basis for all the subsequent models. As for this model,
membrane lipids are arranged in two layers, in such a way that their polar
ends face outwards and non-polar ends face inwards. The proteins occur as
globular proteins and form a continuous layer on either side of the lipid
bilayer. In this arrangement the lipid bilayer appears sandwiched between
the globular protein layers.
Fig. № 2
3
3
1
4
5
2
1234-
integral protein
semiintegral protein
peripherical proteins
hydrophobic tails (non-polar ends)
5-
hydrophilic heads (polar ends)
}lipid bimolecules
b) “Fluid mosaic” model proposed by Singer and Nicolson (1972)
Of all the models, Fluid-Mosaic Model, proposed by Singer and Nicolson, has
the greatest acceptance among the scientists. According to this model the
plasma membrane is made of a lipid bilayer, but the proteins do not form a
continuous layer (Fig. № 2). Instead of it they penetrate into the lipid bilayer
partially or completely. As a result, the plasma membrane acquires dynamic
quality. Both the lipid and the protein molecules have full freedom of mobility
and are capable of translateral movements. Proteins appear like floating
icebergs in a sea of lipid. This model also explains the mechanism involved in
the transport of proteins and enzymes across the cell membrane. It also
describes how the wounds are closed and self healed due to translateral
movements of lipids.
Functions:
1) Barrier function: it helps in isolating the cell interior from the external
environment. Besides, it is the compartmentalization.
2) Transport – some, but not all, substances move or are moved through
membranes by various mechanism.
3) Receptor function: notably hormones from endocrine gland cells and
neurotransmitters from nerve cells bind to binding sites (receptors) of
specific surface proteins of plasmalemma thereby initiating changes in
cell’s activities.
4) Metabolic function: many of the proteins in cytoplasmic membrane are
any enzymes that accelerate (catalyze) an enormous variety of chemical
reactions. Enzymes make possible the chemical reactions that keep our
cells and our bodies alive.
Outline Summary about the Surface Apparatus of
Animal Cell
Structural
Structure
Functions
2
3
components
1
Surface
apparatus
Plasmalemma
Bilipid layer, integral,
semiintegral and
peripherical proteins
- barrier (defensive,
boundary)
Over membrane
complex
(glycocalyx)
Carbohydrate
- transport
molecules, linked with
- receptor
proteins (glycoproteins),
with lipids (glycolipids)
- metabolic
of plasmalemma
- contact (in many
cellular organisms:
in plantsplasmodesmae;
in animals desmosomes)
Nucleus
Nucleus is the most impotent component of a cell.
In the nucleus of eukaryotes four parts are identified. They are:
1) nucleus surface apparatus =
nuclear envelope + pore complex + solid plate (lamina)
2) nuclear sap or karyolymph = karyoplasm + nuclear matrix
3) nucleolus
4) chromatin or chromosomes.
The nuclear envelope is composed of two membranes, separated from each
other by a perinuclear space of 100-500 A˚ widths. Nuclear pores, having a
diameter of 400-1000 A˚, perforate the nuclear envelope. The nuclear envelope
helps in isolating the nuclear material from the cytoplasm, but the nuclear
pores represent the places, where substances are exchanged between the
nucleus and cytoplasm.
Fig. № 3
6
12345678-
nuclear envelope
pore complex
heterochromatin
euchromatin
nucleolus
RNP
karyoplasms
fibrillar proteins
7
6
2
Nucleolus is non-constant component of nucleus. At the beginning of nuclear
division, the nucleolus disappears only to reappear again, at the end of the
nuclear division.
DNA is absent in the nucleolus, but RNA is present in the form of ribonucleic
protein. Along with phospholipids, a variety of enzymes also occurs in the
nucleolus, but histone proteins are absent. Participation in the biosynthesis of
ribosome sub-units is the main function of nucleolus.
The fluid substance presented in the nucleus is called nuclear sap or
karyolymph. Chromatin threads or granules, nucleolus are suspended in this
sap. A number of enzymes - DNA-polymerase, RNA-polymerase, ribonuclease,
alkaline phosphatase etc. also occur in the nuclear sap. They participate in
functions like DNA-replication, transcription and polymerization of messenger
RNA.
Chromatin threads or granules in nondividing cells or chromosomes in early
stage of a cell division present very important, constant components of
nucleus.
The chemical nature of the chromatin is the DNA and proteins molecules.
Proteins covering the DNA molecules are of two types: the basic histones and
the acid nonhistone proteins.
Functions of chromosomes are functions of DNA molecules; they determine
both the structure and the function of cells and heredity. Besides they passed
this heredity information to daughter cells in the process of cell division.
Outline Summary about Nucleus
Surface apparatus
Nucleus
Nuclear envelope
Outer (raffs with ribosomes) and
inner membrane, perinuclear
- barrier (protection
space
of the genetic
Complex of protein globules, apparatus);
Pore complex
Solid plate
(lamina)
Karyoplasm
Nuclear matrix
connected by fibrillar proteins.
Globular proteins in the pore site
are settled in 3 rows 8 globules,
each frequently 1 central globule
is seen (8x3)+1
- transport (inside
the nucleus
histones, enzymes
for replication,
transcription,
ribosomal proteins,
Amorphic protein formation as
nucleotides);
compact layer, connected with
inner membrane
Colloid solution of protein, nucleic - internal medium for
acids
and
other
organic different processes
substances
- support
(“skeleton” of
Fibrillar proteins, forming a dense nucleus)
net in the entire volume of - participation in
nucleus
transcription
DNP (deoxiribonucleoproteid) - storage or
consists of
hereditary
Chromatin
DNA= 40%, proteins= 60% (85% histones, 15% - nonhistones), 1% RNA. There are euchromatin and
heterochromatin.
information;
- transport of
hereditary
information;
- itself reproduction
or replication
Nucleolus
Formed in the area of secondary
constrictions of chromosomes.
There are fibrillar and granular
components
- assembly of
ribosomal subunits
Cytoplasm
Cytoplasm is the inner environment of cell. Within the cytoplasm
1) Cytoplasmic matrix or cytosol (hyaloplasm),
2) Inclusions,
3) Cytoskeleton,
4) Various types of cell organelles are founded.
*Cytosol is a translucent, heterogeneous colloidal substance, which filled
the space between the organelles and inclusions.
*Inclusions are non-constant component of cytoplasm. There are 3 kinds
of inclusions:
various types of nutrients,
pigments,
secretory granules.
*Cytoskeleton of a cell consists of microfilaments, microtubules and
microtrabecular fibers that lay free in the cytoplasm. They are protein
structures and play a role in cytoplasmic streaming or cyclosis and in
other movements, which occur almost universally in an eukaryotic cell,
besides the formation of the cell’s shape.
*Organelles are constant components of cytoplasm. There are 2 types of
organelles.
Cell Organelles
Main cell organelles
Specialized cell organelles
present in any eukaryotic cell
non-membranous
organelles
present only in certain types of cells
membranous
▫ Microvilli – projections of cytoplasm and plasma
organelles
membrane; increase surface area of cells whose function
is absorption.
1. Ribosomes
▫ Cilia – hair like projections of cytoplasm and plasma
2. Centrosomes
membrane; each cilium is a tiny cylinder made up of
3. Microtrabecular fibers
nine double microtubules arranged around two single
4. Microfilaments
microtubules; one cell may have a hundred or more
5. Microtubules
cilia; they propel fluid in one direction over surface of
cell, for example, upward in respiratory tract.
▫ Flagellum – single hair like projection from cells surface
one - membranous
organelles
two-membranous
organelles
1. Endoplasmic reticulum
1. Mitochondria
2. Golgi apparatus
2. Plastids
3. Lysosomes
4. Peroxisomes
for example, flagellum of spermatozoon propels it
forward in its fluid environment.
Main Cell Organelles
Microtrabecular fibers, microfilaments and microtubules
Microtrabecular fibers are the smallest seen fibers, which have a width of
about 3 to 6 nm. They form a three-dimensional, irregularly shaped lattice that
extends throughout cytoplasm, supports various organelles (ER, mitochondria and
so-called free ribosomes). Microtrabecular fibers also serve as cellular “muscles”.
(Actin and myosin, major contractile proteins of muscle cells, have been
identified in microtrabecular fibers.) By contracting and expanding,
microtrabecular fibers control a cell shape and produce internal cell movements
(cyclosis).
Slightly large fibers are suspended in the lattice. They are called microtubules
(200-300 A˚) and microfilaments (40-50 A˚). They and the microtrabecular lattice
together form a supporting framework for the cell or cytoskeleton (Fig. № 4).
Microtubules are the material from which centrioles, basal bodies, cilia,
flagellum and etc are constructed.
Thus, their functions are summarized as follows: they play a role in cyclosis,
transport of substances and cell division, besides contributing to the shape of the
cell.
Fig. № 4
Plasma membrane
Plasma membrane
Centrosomes or the Cell Center
Structure: centrosomes are a small, spherical zone close to the nucleus. In the
center of the centrosome a pair of cylindrical structures, arranged at right angle
to each other is present. They are known as centrioles. Under the light
microscope, centrioles appear as two dots located near the nucleus. They are 0,4
μm long with a diameter of 0,2 μm. The electron microscope, however, reveals
them not as mere dots but as tiny cylinders of microtubules, with three tubules in
each bundle. The rest of the centrosome is known as centrosphere (Fig.№5).
Centrosomes have own DNA.
Fig. № 5
1 - daughter centrioles
2
2 - mother centrioles
3
1
3 - centrosphere
3
Function: at the beginning of the nuclear division the centrioles replicate and
move to the opposite poles. They are responsible for the formation of mitotic
spindle or the mitotic apparatus (achromatic apparatus).
Ribosomes
Ribosomes are exclusively confined to the cytoplasm. They are not found
in the nucleus. Their names are ribonucleoprotein particles (RNP). They are
mainly composed of proteins and ribonucleic acid (RNA). The ribosomes
account for about 85% of the RNA present in a cell.
They occur either freely in the cytoplasm, mitochondrial matrix and
stroma of plastids or bound to the outer surface of the endoplasmic
reticulum.
Ribosomes are of spheroid structures. They are made of two sub-units –
one small and one big (Fig. № 6). Sub-units of ribosomes synthesize in
nucleolus, but their combination in the entire ribosome takes place in
cytoplasm. When the concentration of magnesium ions (Mg 2+) is 0.001 M, the
sub-units of a ribosome are joined together. They dissociate from each other
when the
Mg2+concentration is less than 0.001 M. When the Mg2+ ion
concentration is increased ten times, i.e. raised to 0.01 M, two ribosome join
together, producing a ‘dimmer’ or twin ‘particle’. During protein synthesis
many ribosomes are attached to the m-RNA strand like beads on a string and
the chain of beads move along the m-RNA strand. This chain of ribosomes is
called polyribosome or polysome. They form characteristic whorled pattern
on the endoplasmic reticulum.
1
Fig. № 6. 70S- ribosomes
2
1 – small sub – unit
1
2 – big sub – unit
2
Function: participation in the protein synthesis is the main function of
ribosomes-“protein factories”. During protein synthesis, in addition to serving
as workbenches, they participate in the catalytic actions of chain initiation,
elongation and termination of a polypeptide chain.
Endoplasmic reticulum
Studies carried out with the electron microscope have revealed the presence
of a complex membranous labyrinth in the cytoplasm. It is called endoplasmic
reticulum. It even spreads throughout the cell, as a complex interlacing
membranous structure. It may establish contact with the nuclear membrane on
one side and the plasma membrane on the other side. Sometimes, it is associated
with the Goldi complex also.
The endoplasmic reticulum is composed of three types of membranous
structures:
- Cisternae,
- Vesicles,
- Tubules .
Cisternae are the most important structures of endoplasmic reticulum. They
appear a stack of parallely arranged structures in the cross section. Each
cisterna is 50-60 μm thick. The cisternae are highly developed in the cells
involved in protein synthesis and secretory activity (e. g. cells of pancreas, liver,
neurons etc.).
Vesicles are found in abundant numbers in cells of organs like pancreas and
do not possess a definite shape and size. They have a diameter of 40-500
millimicrons.
Tubules are highly branching and anastomosing structures, with a diameter
of 50-190 µm. They are associated with both the cisternae and vesicles.
Depending upon the metabolic state of a cell, these membranous structures
exhibit transformation from one form to another (i.e. cisternae to vesicles,
vesicles to tubules, vesicles to cisternae etc.) The membrane structure of the
endoplasmic reticulum is variable in different species. Even within the same
species variability exists in different types of cells. But a similar structural
pattern is seen in all the cells carrying out the same physiological function.
Types: the endoplasmic reticulum occurs in two broad types – rough
endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). The
morphological distinction between RER and SER depends on the distribution of
ribosomes. When ribosomes are attached to the outer surface of the
endoplasmic reticulum it appears rough or granular and so, described as rough
endoplasmic reticulum. In the absence of ribosomes, it appears smooth and
known as smooth endoplasmic reticulum. Cisternae, vesicles and tubules are
well developed in RER. In SER, tubules are well developed forming an
interlacing system.
In a large number of cells RER and SER are
observed interconnected and transport of materials from RER to SER has been
noticed. As per the need of a cell, RER and SER are interchangeable.
Functions: 1). SER participates in the synthesis of lipids (steroids).
2). SER participates in the synthesis of carbohydrates (glucose), secretes the
enzyme glucose-6-phosphatase and converts glucose-6-phosphate into glucose
in the liver. (Plasma membrane prevents escape of glucose-6-phosphate but
allows glucose to leave the cell.).
3). RER participates in the synthesis of proteins and enzymes.
4). ER plays an important role in the structural and transportation systems of a
cell: canals of reticulum serve for the cell as its inner circulatory system, for
example, proteins move through canals on way to Golgi complex.
Golgi apparatus
Golgi complex was first discovered and described by Camillo Golgi in
1898.This specialized organelle, in the cells, exhibits some degree of variability
in structure, in different types of cells. It is well developed in the cells involved
in high secretory activity. Golgi apparatus generally occupies a position near
the pole or between the pole and the nucleus. However, there are cells in
which, it is distributed anywhere in the cytoplasm.
The structural and functional unit of GA is dictyosome. In plant cell the
number of dictyosomes more than in an animal cell. Every dictyosome appears
as an assemblage of three types of membranous structures:
- Cisternae or flattened sacs,
- Vesicles,
- Micro vesicles.
Cisternae are flattened sac-like structures with a diameter of 0.5-100 A˚. Of
these, four to eight are arranged one above the other, like a stack of pancakes
(Fig 7). The number of such stacks varies from one to a few thousands,
depending upon the nature of the cell. The stacks are concave structures, with
a shallow cup-like appearance. The cisternae of a stack are separated from
each other by a gap of 250-300 A˚. Interconnections between the cisternae
have not been observed.
Fig. № 7
3
2
1- secretory granules
1
2- condensing vesicle
3– inner face or trans – face
(maturing face)
4
4– sacs or cisternae
5 – micro vesicles
6– outer face or cis-face
(forming face)
5
6
Golgi complex is closely associated with the SER. Cisternae of the Golgi
complex closest to the SER is called cis-face or outer-edge of the stack. The
membrane thickness of this cisterna is 50-60 A˚ and it closely resembles the ER
in structure. The farthest cisterna of the stack (from the SER) is known as the
trans-face or inner edge of the stack. Structurally, the membrane of this cistern
resembles plasma membrane and it has a thickness of 75-100 A˚. In most of the
cells, the edges of the cisternae, particularly the ones towards the trans-face,
appear dilated. It is believed that the vesicles are budded off from these
dilations. As ribosomes are absent, the membrane of Golgi complex appears
smooth.
The precise relationship between the ER and GA is often unclear. In case of
pancreatic cells, RER is found associated with SER and continuous formation of
micro vesicles has been observed from the edges of SER. These vesicles
probably act as transport vesicles carrying the substances synthesized in the
RER to the GA. At the cis-face of GA, the vesicles fuse forming new cisternae.
For this reason the cis-face is also known as «forming face». Thus, as the new
cisternae are being added at the cis-face, the cisternae at the trans-face break
up into vesicles. So, the trans-face is also known as «maturing face».
For carrying out the studies on polypeptide synthesis, through pulse-chase
experiments labelled aminoacids are employed. Such experiments have shown
that, newly synthesized pancreatic enzymes take 10-20 minutes time to reach
the Golgi complex, from the site of their synthesis in RER, about 40 minutes to
enter the condensing vesicles and about 2 hours to leave the cell. In some cells,
existences of direct connections between the ER and GA have been noticed.
The condensing vesicles develop from the maturing face of the GA. The are
described as secretory granules, after the process of condensation is over. The
secretory granules travel towards the cell membrane, fuse with it and release
their contents into the cell exterior.
Therefore, Golgi complex is considered as a transitional organelle between
the endoplasmic reticulum (ER) and plasma membrane.
Functions:
1. Participates in the processing, packing and distribution of the substances
2.
3.
4.
5.
6.
synthesized in the RER.
Synthesizes large carbohydrate molecules (cellulose).
The chemical substances synthesized in the ER are subjected to cyclical
changes in the GA: combines large carbohydrate molecules with proteins
and secretes product (glycoproteins).
Participates in the condensation of secretory “products”
Participates in the formation of lysosomes
GA is involved in the formation of plasma membrane, in dividing of plant
cell (cytokinesis), in producing a cap-like acrosome on the head of the
sperm. The hydrolases present in the acrosome facilitate fertilization by
dissolving the egg membranes. Also it partakes in the synthesis of yolk in
the egg cells.
Lysosomes
In 1949, de Duve along with his colleagues discovered and named this
cell organelle as lysosome. Lysosomes carry more than 40 acidhydrolases.
Lysosomes exhibit great variation in their shape and size. They are
spherical, rod-shaped or irregular in shape and have a diameter of 250 A˚ to 1
µm. Lysosomes are temporary structures, surrounded by a lipoprotein
membrane. The method of their formation closely resembles the formation of
secretory granules in the Golgi apparatus. This process is summarized as follow:
1) The synthesis of lysosomal enzymes in the RER
2) Their transportation to the GA
3) Their packaging into lysosomes from the trans-face of the Golgi complex.
Lysosomes exhibit polymorphism. Four types of lysosomes are
identified:
* primary lysosomes,
* digestive vacuoles or secondary lysosomes (heterophagosomes),
* residual bodies,
autophagic vacuoles (Fig 8).
*
lipofuscin
granule
Fig. № 8
Primary lysosomes are also known as storage granules. They are minute
granular structures filled with hydrolases synthesized in the ribosome, attached
to the RER.
Digestive vacuoles are also known as heterophagosomes or secondary
lysosomes. Phagosomes or phagocytic vesicles are formed in the cells due to
endocytosis of food or phagocytosis of harmful microorganism.
When primary lysosomes fuse with these structures, digestive vacuoles
(heterophagosomes) are formed. They contain substances at different stages of
digestion.
Residual bodies after digestion and absorption of digested food
(aminoacids, glucose, fatty acids and glycerol) into the neighboring cytoplasm,
the digestive vacuoles are left with undigestible food. Now they are called
residual bodies. They come to the cell surface, fuse with the cell membrane
and discharge their contents to the outside (exocytosis)
In case of vertebrates, a suitable mechanism is absent in the cells for
the removal of these residual bodies. As a result, they get accumulated in the
cytoplasm and are known as lipofuscin granules. Their number increases with
the increasing age of the cell. This type of accumulation is very well
represented in the nerve cells, which have a long life span. This may be the
main cause for the ageing process in animals.
Autophagic vesicles lysosomes also participate in the digestion of cell
organelles like mitochondria and ribosomes, this phenomenon is called
autophagy. Due to injury, poisoning old age or oxygen deficiency, lysosomes,
rupture releasing their enzymes into the cell. Consequently, the cell itself is
digested. This is called autolysis or self-destruction
Functions: participates in the digestion of the substances entering the
cell. For this reason lysosomes are known as “suicidal bags”, “bags of
destruction” or “autolytic vesicles”.
Heterophagy: lysosomes participate in the digestion of material present in the
phagosomes (vacuoles with solid food) and pinosomes (vacuoles with liquids)
Autophagy: lysosomes are also involved in the digestion of other cell organelles
like mitochondria, ribosomes, ER, etc.
Peroxisomes
Peroxisomes are membrane-bounded sacs of enzymes that carry out
oxidation reactions in which they combine oxygen with various substrates.
They are named for hydrogen peroxide (H2O2), which some of these enzymes
make. Another peroxisome enzyme, catalase, uses hydrogen peroxide to
detoxify harmful substances, especially in the liver and kidneys. For example,
peroxisomes detoxify about half the ethanol we consume.
In modern eukaryotic cells most oxidation takes place in
mitochondria during cellular respiration. Some biologists think peroxisomes are
the remnants of ancient oxidizing organelles that have largely been supplanted
by mitochondria. The advantage of mitochondria over peroxisomes is that the
major product of the oxidation reactions is ATP, which the cell can use for
energy.
Mitochondria
The term mitochondrion means thread, granule (GK. “mito” -thread;
“chondrion” - granule). Its plural from is mitochondria. Kolliker observed them
first in a muscle cell in 1850. Benda employed a new staining technique, gave a
detailed description of its external structure and called it
"mitochondrion" in 1898.
Mitochondria are very important cell organelles, as they carry a unique
chemical and structural system for the synthesis of ATP. ATP is the chemical
energy required for carrying out various metabolic activities in cells. Because of
this, mitochondrion is rightly described as a " power plant " or " power house "
of a cell. Mitochondria are also semiautonomous and self - replicating cell
organelles. New mitochondria always develop from pre - existing mitochondria,
through division. In 1890 Altmann expressed the view that mitochondria are
probably bacteria leading a symbiotic life in the cells.
Mitochondria display various shapes. Mitochondrial number depends on
the functional status of a cell.
Electron microscopic studies reveal that mitochondria are made of two
membranes of different nature. They are outer and inner membranes. The
outer membrane encircles the mitochondrion completely and serves as its outer
boundary. The inner membrane produces a number of inward foldings known
as “cristae”. The cristae increase the inner surface, providing space for the
components of the respiratory chain. The inner cavity of mitochondrion is
described as " inner chamber". It is filled with a jelly - like substance, the matrix.
Its jelly - like appearance is due to the presence of a high concentration of
soluble proteins. The cavity presented between the outer and inner
membranes is known as " inter — membrane space " or " outer chamber " (Fig
9). It is filled with a watery fluid. The inner membrane space is continuous with
the space present within the folds of cristae.
With the help of electron microscope, Humberto - Fernandez - Moran
observed a number of lollies - pop - like structures attached to the innerside
of the inner membrane. They are known as oxysomes, as they carry
oxidative enzymes. They are also called elementary particles, Fl - particles or
Fernandez -Moran particles. Each Fl - particle has three parts VIZ; the head
piece, the stalk and the base piece (Fig 9).
Fig. № 9
Oxysomes containing enzymes
attached by stalks to inner
membrane
Outer membrane
Inner membrane
cristae
The mitochondrial matrix includes a variety of items not found in other cell
organelles. They are ribosomes (smaller than those found in the
cytoplasm), circular DNA molecules, filaments, dense granules and
enzymes of Krebs’s cycle. The circular DNA molecules help in the
synthesis of RNA and proteins required by the mitochondria. One type of
dense granules is presented in the matrix store calcium ions, in the form
of precipitates of calcium phosphate. The calcium ions play an
important role in the regulation of numerous biochemical activities
within the cell. Mitochondria thus act as calcium accumulators.
Besides, mitochondria are also involved in heat generation. The heat
generated by mitochondria helps in the maintenance of constant body
temperature in homoiotherms or warm-blooded animals (aves and
mammals).
Plastids
These are the universal important organelles presented only in cells of
plants.
There are three kinds of plastids:
•
Chloroplasts (the green plastids)
•
Chromoplasts (the yellow or orange - red plastids)
•
Leucoplasts (the colorless plastids)
They are different in the structure and functions, but all plastids take part
in synthesis of carbohydrates. Like mitochondria, plastids carry some of their
own hereditary material in the form of a circular molecule of DNA and
ribosomes in stroma. They are duplicated by division. Chloroplasts are the
green plastids. They act as photosynthetic apparatus. The entire process of
photosynthesis is completed in each chloroplast. Hence, these are the sites of
photosynthetic reactions.
Leaves are the specialized photosynthetic organs and hence, they contain
maximum number of chloroplasts in their mesophyll cells. Moreover,
morphology and anatomy of leaves are most helpful during photosynthesis for
getting maximum benefit of sunlight providing steady supply of water to green
cells and allowing free exchange of CO2 and O2.
Structure: the chloroplasts in higher plants are microscopic and mostly
oval, spherical or discoid. Each chloroplast is bounded by two smooth and
selectively permeable cytoplasmic membranes with an inter - membrane space.
These membranes are composed of lipoprotein sub - units.
The internal space of the chloroplast is filled with a colorless hydrophilic
matrix called stroma. Numbers of grana are suspended in the stroma. Each
granum is a stack (compact bundle) of thylakoids. These are membrane bound flattened, disc - shaped vesicles. The thylakoid membranes are called
grana lamellae. All grana are connected with one another by stroma lamellae,
i.e. inter - grana lamellae or frets. Internal space of each thylakoid is called fret
channel.
The thylakoid lamellae are composed of alternating layers of lipids and
aqueous proteins. There is a layer of chlorophyll and carotenoid molecules
situated between the protein and lipid layers. The chlorophyll molecules are
arranged in such a way that their hydrophilic heads extend into the aqueous
protein layer while the lipophilic tails are embedded in the lipid layer.
The pigments are organized into numerous photosynthetic units called
quantasomes. Each quantasome contains about 230 to 300 chlorophyll
molecules. Quantasomes are capable of trapping light energy and converting
into chemical energy (ATP) during the photochemical reactions (light reaction of
photosynthesis). The grana also contain various co — enzymes and
electron acceptors necessary for the process. Hence, grana are the site of
the light reaction (phase -1) in photosynthesis.
The stroma contains various enzymes required for the dark reaction i. e. the
biochemical reactions involving the reduction of CO2 to form carbohydrates.
Hence, stroma is the site of dark reaction (phase - II) of photosynthesis.
The grana thylakoids and the stroma lamellae together form an intricate
internal membrane system in the chloroplast. This system is derived from the
inner limiting membrane during the development of chloroplast.
Pigments in photosynthesis: the most common photosynthetic pigments
presented in higher plants and green algae are:
Chlorophyll-A (blue-green)=C55H72O5N4Mg
Chlorophyll-B (yellow-green)=C55H70O6N4Mg
Carotenoids:
*Carotenes (orange-red) = C40H56
*Xanthophylls (yellow)= C40H56O2
For photosynthesis, these pigments can absorb and use light belonging to
the visible spectrum only.
Both chlorophyll-A and B show light absorption maximum in red followed by blue
and then in violet regions. Absorption of green light by the chlorophylls is
negligible. In fact, chlorophylls reflect green light and hence appear green.
Carotenoids absorb light in the blue, green and violet regions. Carotenes
reflect orange light therefore appear orange. Xanthophylls are yellow colored
because they reflect yellow light.
Carotenoids protect the chlorophyll from undergoing photo oxidation
when exposed to very high light intensity.
Chlorophyll-A is the essential pigment in photosynthesis, because only
chl-A can utilize the absorbed light energy for the synthesis of chemical energy
ATP. Other pigments act as accessory pigments. They collect the light energy and
transfer it to chlorophyll-A for photosynthesis.
Thylakoids in prokaryotes: In prokaryotes like cyanobacteria, purple
bacteria, etc. thylakoids are present but they lie scattered and not organized
into grana. Grana or the chloroplasts are absent. In prokaryotes, pigments
are distributed uniformly on or in the lamellae.
Functions of plastids:
1) The chloroplasts participate in the synthesis of primary
carbohydrate (glucose).
2) Chromoplast and leucoplast take part in the synthesis of
secondary carbohydrates (starch). Chromoplasts are contained in cells of plant
colored organs (for example, flowers, fruits, etc.)
The leucoplasts are placed in cells of plant colorless organs. There are seeds,
spores or subterranean organs of plants (roots, bulbs tubers, etc.).
Outline Summary about Organelles
Hyaloplasm
(cytoplasmic
matrix)
Colloid solution of proteins containing
organic and mineral substances
- internal medium of the cell, providing
process of metabolic reactions
- synthesis of lipids
m
Smooth ER – system of canals, formed
with membranes
Endoplasma-
- transport
-compartmentalization
Rough (granular) ER- system of
flattened cisternae and canals bearing
ribosomes on outer surface
- synthesis of proteins
- maturation of proteins
- transport
s
a
s
tic reticulum
(ER)
- synthesis of oligosaccharides
l
e
- compartmentalization
l
Mitochond-
e
n
g
Golgi
apparatus
(Golgi body)
O
r
t
- synthetic (synthesis of proteins)
- compartmentalization
System of flattened membranous sacks
(cisternae), surrounded by a number of
micro and macrovesicles (vacuoles).
Cis-side of GA is located closer to
nucleus, contains microvesicles. Transside of GA contains macrovesicles,
forming vacuolar zone of GA.
C
y
- energy accumulation (synthesis of
ATR)
- genetic (replication of DNA)
a
o
p
l
rion
Outer- smooth membrane, inner – with
crystae. Intermembrane space- matrix;
DNA, ribosomes, proteins and
inclusions.
- maturation, reassortment of protein
- formation of primary lysosomes
- formation of secretory granules
- synthesis of polysaccharides
- synthesis of lipids
- detoxification
- compartmentalization
Lysosome
Vesicle, bounded by membrane, with
homogenous contents (set of
hydrolases)
- heterophagy
- autophagy
- compartmentalization
Peroxisome
Ribosome
Microtubules
Microfilaments
Vesicle, bounded by membrane, with
crystal-like contents (catalases)
- participation in peroxide oxidation
Small and large subunits
- synthesis of proteins (translation)
Hollow cylinder, formed with spirally
packed dimmers of protein (tubulin)
- movement (basis of cilia and flagella);
Actin (main amount). Myosin
- contractive
- compartmentalization
- participation in the division of the
cells (basis of mitotic apparatus)
-formation of desmosomes
Cell centre
Cilia and
flagella
Inclusions
Diplosome (2 centrioles) and
centrosphere. Each centrioles is
cylinder, consisting of 9 triplets of
microtubules (9x3)+0
- participates in cell division
(formation of mitotic apparatus)
Cytoplasmatic protrusions (length 1012μm-cilia, > 1000 μm -flagella),
covered by plasmalemma
- movement of a cell (unicellular
organisms);
Temporary intracellular structures,
accumulated and used during
metabolism
- nutrition (carbohydrates, lipids)
- transport of the particles and fluid
- secretory
- pigment (melanin, haemoglobin)
Cytoskeleton
Microtubules, microfilaments and
microtrabecular fibers free lied in
cytoplasm
- “skeleton” of cell
- cyclosis
BIBLIOGRAPHIC REGISTER:
1. Intermediate First Year, ZOOLOGY Intermediate: (First Year) ZOOLOGY:
AUTHORS (English Telugu Versions): Smt. K.Srilatha Devi, Dr. L. Janardhan Rao,
Dr. T. Vishnumoorthy, Dr. S. Sivaprasad; EDITOR: Prof. T. Gopala Krishna Reddy,
Revised Edition: 2000.
2. A textbook of cytology, genetics and evolution, ISBN 81-7133-161-0, P.K.
Gupta (a text-book for university students), published by Rakesh Kumar Rastogi
for Rastogi publications, Shivaji Rood, Meerut- 250002.
3. Science of biology (the study of life science) Higher Secondary Std. XII, J.D.
Sahasrabuddhe, S.P. Gawali, Eighth Revised Edition: 2002, Himalaya Publishing
House.
4. Biology, fourth edition, Karen Arms, Pamela S. Camp, 1995, Saunders college
Publishing.
5. Review Committee, Dr. K. Malla Reddy, Sri Y. Krishnanandam, Sri B.V.
Gopalacharyulu, Sri G. Rama Joga Rao, Teludu Akademi.
CONTENTS:
1. Introduction…………………………………………………………… 4
2. Forms of life…………………………………………………………… 5
3. Comparison of prokaryotic and eukaryotic cells…………………… 6
4. Structure of eukaryotic animal cell………………………………….. 7
5. Plasmalemma………………………………………………………….. 8
6. Outline summary about the surface apparatus of a cell……………. 9
7. Nucleus…………………………………………………………………. 10
8. Outline summary about nucleus……………………………………… 11
9. Cytoplasm……………………………………………………………… 12
10.Cell organelles (diagram)……………………………………………...13
11.Main cell organelles…………………………………………………. 14
11.1. Microtrabecular fibers……………………………………… 14
11.2. Microfilaments, microtubules………………………………. 14
11.3. Cell center……………………………………………………. 15
11.4. Ribosomes……………………………………………………. 15
11.5. Endoplasmic reticulum……………………………………... 16
11.6. Golgi apparatus……………………………………………… 17
11.7. Lysosomes……………………………………………………. 19
11.8. Peroxisomes………………………………………………….. 21
11.9. Mitochondria………………………………………………… 21
11.10.Plastids………………………………………………………. 23
12.Outline summary about organelles…………………………………. 26
MATERIALS FOR PRACTICAL WORKS ON CYTOLOGY
Textbook for students of the English – speaking Medium
Материалы к практическим занятиям по цитологии
Учебное пособие для студентов англоязычного отделения
(на английском языке)
Авторы: Макаренко Элина Николаевна, кандидат медицинских наук,
старший преподаватель кафедры биологии с экологией; Болдырева Галина
Ивановна, старший преподаватель кафедры биологии с экологией;
Паршинцева Наталья Николаевна, старший преподаватель кафедры
иностранных языков с курсом латинского языка.
Authors: senior lecturers of Biology with Ecology department Makarenko E.N.,
Boldyreva G.I., teacher of Latin and foreign languages department of Stavropol
State Medical Academy Parshintseva N.N.
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