Practice 1 Cellular Biology

8/2/2019 Practice 1 Cellular Biology

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BIOLOGY AS A SCIENCE.

INTRODUCTION TO CELL BIOLOGY

CHAPTER 1: Biology is a science of living matter.

1.1. Biology as а science of life. Biology is a branch of the natural sciences which studies living organisms and

how they interact with each other and their environment. It examines the structure,

function, growth, origin, evolution, and distribution of living things. Also, it

classifies and describes organisms, their functions, and how species come into

existence.

The word "Biology" has been derived from two Greek words, “bios-“ and “–

logos”. “ Bios“ means life and “logos” means thought, discourse or reasoning. The

term “Biology” was coined by Lamarck and Treviranus in 1802.

Biology literally means "the study of life". Biology is such a broad field, cov-

ering the minute workings of chemical machines inside our cells, to broad scale

concepts of ecosystems and global climate change. Biologists study intimate de-

tails of the human brain, the composition of our genes, and even the functioning of

our reproductive system. Biologists recently all but completed the deciphering of

the human genome, the sequence of deoxyribonucleic acid (DNA) bases that may

determine much of our innate capabilities and predispositions to certain forms of

behavior and illnesses. DNA sequences have played major roles in criminal cases.

We are bombarded with headlines about possible health risks from favorite foods(Chinese, Mexican, hamburgers, etc.) as well as the potential benefits of eating

other foods such as cooked tomatoes. Infomercials tout the benefits of metabolism-

adjusting drugs for weight loss. Many Americans are turning to herbal remedies to

ease arthritis pain, improve memory, as well as improve our moods.

Four unifying principles form the foundation of modern biology: cell theory ,

evolution , gene theory and homeostasis .

1.2. The main disciplines of Biology.Biology is subdivided into many branches, depends on the subject-matter and

object of study. Biology includes some disciplines:

1. Morphology, it deals with the form and structure of organisms. It com-

prises several branches:

a) Anatomy, it deals with the structures visible to the naked eyes such as

in the dissection of organisms.

b) Histology, it is the study of finer details of structure of organs and tis-

sues with the help of a microscope.

c) Cytology, it is the detailed study of structures and functions of cells.

http://en.wikipedia.org/wiki/Natural_sciences

http://en.wikipedia.org/wiki/Organism

http://en.wikipedia.org/wiki/Species

http://en.wikipedia.org/wiki/Cell_theory

http://en.wikipedia.org/wiki/Evolution

http://en.wikipedia.org/wiki/Genetics

http://en.wikipedia.org/wiki/Homeostasis

http://en.wikipedia.org/wiki/Natural_sciences

http://en.wikipedia.org/wiki/Organism

http://en.wikipedia.org/wiki/Species

http://en.wikipedia.org/wiki/Cell_theory

http://en.wikipedia.org/wiki/Evolution

http://en.wikipedia.org/wiki/Genetics

http://en.wikipedia.org/wiki/Homeostasis



d) Embryology, it is study of formation, growth and development of a

new individual generally from an egg.

2. Physiology, it is the study of working and functions of organs within an or-

ganism.

3. Ecology, it is the study of relations of living things and their environment.

4. Taxonomy, it is the study of laws and principles of a natural classificationof organisms.

5. Evolution, it is the study of origin, differentiation, and interrelationships of

organisms of the present day and past ages.

6. Genetics, it is the study which accounts for resemblances and differences

in the offspring due to variations in germ cells, and the mechanism of passing of

these characters from one generation to the next.

7. Molecular Biology, the study of living things in terms of Physics and

Chemistry of the molecules making up the living matter is called the Molecular Bi-

ology.8. Radiation Biology, since the first use of atomic bomb by USA on Japan

in August 1945, investigations on the effects of invisible rays and radiations on the

living organisms has become an important discipline of biology. Besides the use

of radiations as a weapon in wars, many beneficial uses of radiations have been

discovered, specially in plant breeding and creating new varieties of seeds.9. Space Biology, the newest of biological sciences deals with the space travel

and its problems affecting the main and other organism on planets other than the

earth; chief of which are concerned with are concerned with respiration, food, en-

vironment and cosmic radiations.10. Toxicology. In factories and mines around the world, hundreds of thou-

sands of workers are daily exposed to a large variety of toxic or poisonous sub-

stances that lead to deadly diseases as pneumoconiosis, silicosis, fetal disorders,

paralysis and skin allergies. In textile industry workers constantly inhale flour dust

which is suspected to cause dermatitis and tuberculosis, asbestos dust in asbestos

workshops causes lesions in the lungs, pesticides used un the storage of grains

are known to cause serious diseases in the consumers; silica dust in the factories

ma king bangles and other glass-wares causes allergies.

Some of the important interdisciplinary biological sciences are Protozoolo-

gy (of Protozoa), Limnology (of fresh water pond community), Helminthology(of flat and round worms), Entomology (of insects), Malacology or Concholo-

gy (of snails), Ichthyology (of fishes), Carcinology (of Crustacea), Herpetology

(of Amphibia and Reptilia), Ornithology (of birds) and Parasitology (of para-

sites).

1.3. The main characteristics of living and non-living substances.Living organisms can usually be distinguished from the non-living though this

is not easy with lower forms of life. All living beings display the following prop-

erties:

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1). Form and size. Each living being usually has a definite form and charac-

teristic size, it is an organized individual with a centralized control, and an interde-

pendence of its parts. There is no limit to form or size of non-living substances and

they have no centralized control.

2). Chemical composition. Living organisms are composed of chemical

substances in definite proportions; these chemicals form complex organic mole-cules (lipids, sugar, proteins and nucleic acids) of great molecular weight which

collectively form a living substance. Non-living substances may have the same el-

ements as found in protoplasm but they lack life.

3). Nutrition and growth. Living beings require nutrition or food which is

used for building the body and repairing worn-out parts and also for supplying

energy for their vital activities. Constant nutrition forms new protoplasm which re-

sults in growth or an increase in size and weight. In growth, formation of new

parts occurs within or between older ones, and the food taken in for growth is

different from the living protoplasm it forms. In non-living matter there is noneed for nutrition though a non-living body such as a motor car requires fuel for its

energy. If growth occurs in a non-living object, such as a crystal, it is due to the

addition of material on the outside, this material is chemically the same as the non-

living object.

4). Excretion. Certain compounds of nitrogen, water, and carbon dioxide are

constantly formed in the living body, they are called excretory products; they are

not needed and may even be harmful. Consequently they have to be got rid of the

elimination of nitrogenous wastes is called excretion. But excretion does not in-

clude faeces because it was never a living part of the body. No excretion occurs in

non-living substances.

5). Release of energy. All living organisms need energy for work. The ener-

gy comes from the breakdown of a chemical called adenosine triphosphate (ATP)

into its diphosphate form (ADP). Energy is required to convert ADT into ATP.

This energy comes from the oxidation of food, chiefly sugar. Oxygen is breathed

in from air or water and utilized in the living body. The oxygen there forms

waste CO2, which is eliminated from the body. Several complex chemical changes

take place in the production of usable energy by oxidation of food. Steps from

breathing in of oxygen to the release of energy and the restoration of ATP are put

into one word, the respiration. There is no respiration in non-living objects.6). Metabolism. Various vital chemical changes take place constantly in liv-

ing organisms, these changes are collectively called metabolism. In metabolism or-

ganic substances are changed into new organic substances which replace old parts

and build the body, but through all these ceaseless changes the animal remains

more or less the same, though its protoplasm is being constantly broken down and

then made anew. Organisms take in food and oxygen to form molecules of proto-

plasm, this constructive process is called anabolism in which chemical energy is

stored as potential energy. Then the molecules of protoplasm are broken down to

change potential energy into kinetic energy which is used for carrying on loco-

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motion and various vital activities of the organism, at the same time waste sub-

stances such as urea, salts, water, and CO2 are produced. This breaking down

process is called katabolism (or catabolism) in which loss of weight, fatique, hun-

ger, and thirst result. There is no metabolism in non-living substances; if they show

locomotion, the energy comes from an external source. If an organism is to live,

both anabolism and katabolism must go on. If anabolism exceeds katabolism,growth takes place in the young, but during adult life excess anabolism is used for

producing sex cells; in old age katabolism overtakes anabolism which eventually

results in death.

7). Irritability. Living organisms react to changes in their environment. The

environment may be terrestrial, aquatic, aerial, or parasitic. Any change in the en-

vironment to which an organism responds is called a stimulus, and the capacity of

an organism react to stimuli constitutes its irritability. The stimuli may be external

(such as heat, light, chemical substances, pressure or gravity), or they may be inter-

nal (such as hunger, thirst, pain). Irritability is a fundamental property of protoplasm, it is not found in non-living substances.

8). Reproduction. Each living organism has the ability to duplicate it selves

or produce new individuals resembling it in all essential features. Reproduction is

the unique property possessed on the by the living, and they reproduce by using

their own body material. The methods of reproduction are many and varied but all

of them maintain a continuity of the race. Non-living substances cannot reproduce.9). Adaptation to environment. Every living organism fits itself to its sur-

rounding or it is adapted to the conditions of life called the environment . This per-

fect adaptation fits a living organism to procure food, protect itself, and rear its

young ones. But the environment may not remain constant for long periods of

time, hence the living organism in order to continue to live or survive, must re-

adjust itself to the changed conditions of environment. the ability to adapt them-

selves to their environment is the characteristic property of living organism. Non-

living objects may or may not be adapted to their environment. A star may be

adapted to its cosmic system but it cannot adjust itself to any changed conditions of

the environment.

10). Aging and death. Every living system is subject to aging after certain

length of time. As described earlier a time comes when katabolism takes over an-

abolism. In other words, there is more wear and tear than growth and repair body'sresistance to stresses and stains weaken and there cracks develop in the body's de-

fenses against diseases and foreign bodies. Overall effect of these weaknesses

causes aging and eventual death.

11). Homeostasis. Homeostasis is the maintenance of a constant (yet also dy-

namic) internal environment in terms of temperature, pH, water concentrations,

etc. Much of our own metabolic energy goes toward keeping within our own

homeostatic limits. If you run a high fever for long enough, the increased tempera-

ture will damage certain organs and impair your proper functioning. Swallowing of

common household chemicals, many of which are outside the pH (acid/base) levels

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http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossH.html#homeostasis

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossPQ.html#pH

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossH.html#homeostasis

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossPQ.html#pH



we can tolerate, will likewise negatively impact the human body's homeostatic

regime. Muscular activity generates heat as a waste product. This heat is removed

from our bodies by sweating. Some of this heat is used by warm-blooded animals,

mammals and birds, to maintain their internal temperatures.

1.4. Levels of biological organization.The molecular-genetic level is the simplest level of biological organization. It

includes the basic particles of all matter, atoms and combinations of atoms called

molecules. This level is about chemical elements, inorganic and organic molecules

and hereditary material (DNA and RNA).

Subcellular (cell organelle) level. Many diverse molecules may associate and

form highly specialized structures of a cell called organelles. The plasma mem-

brane that surrounds the cell and the nucleus that contains the hereditary material

are example of cell organelles. The organelles are suspended within (or surround)

the jelly-like cell cytoplasm.At the cellular level we find a cell that is the basic structural unit of life, the

simplest part of living matter that can carry on all of the activities necessary for

life.

In most multicellular organisms, cells associate to form tissues - group of cell,

having the same origin, structure, and fulfilling the same functions (tissue level ),

such as muscle tissue in animals or epidermis in plants.

Tissues arranged into functional structures called organs (organ level ), such as

the heart or stomach in animals or root and leaves in plants.

Each major group of biological functions is performed by a coordinated groupof tissues and organs, called an organ system. The circulatory and digestive sys-

tems are the examples of organ systems (system level ).

Functioning together with great precision, the organ systems make up the

complex multicellular organism (organism level ).

Organism interacts to form still complex levels of biological organization. All

members of one species that live in the same area, mate and give the progeny

called a population ( population level ).

Populations which are phenotypically similar and reproductively isolated from

the other, but actually or potentially capable of interbreeding among themselvesform the species (species level ).

The populations of organisms of different species that inhabit a particular area

and interact with each other make a community or biocoenosis (biocoenosis level or

ecosystem level ). The community can be composed of hundreds of different types

of life forms.

A community together with its non-living environmental factors is referred to

as an ecosystem ( ecosystem level).

All communities of living things on Earth are collectively referred to as the

biosphere (biosphere level ).

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CHAPTER 2: Cellular organization of living matter.

2.1. Historical backround on the development of Cell Biology.The cell is a fundamental to biology as the atom is to chemistry. In the hierar-

chy of biological organization the cell is the simplest collection of matter that can

live.

Cell biology has achieved recognition as an independent discipline only dur-

ing the past 50 years. Just as biochemistry involved at the beginning of this

century from the fusion of physiology and organic chemistry, so cell biology

developed by integrating knowledge gained in microscopic anatomy and bio-

chemistry. Cytology began in the mid-17th century when the first microscopists -

in particular Malpaghi and Hook - began to describe the structural components of living matter. The history of the cell begins with the publication of the classical

work « Micrographia" in London by Robert Hook in 1665. He observed a hon-

eycoumb-like pattern in a slice of cork under his primitive microscope. This hon-

eycomb consisted of thick-walled, box-like compartment which he called cells for

the first time. But he did not realize the real significance of these structures.

In 1674 Antony Van Leeuwenhoek improved the lens system of this micro-

scope and was the first to observe bacteria, various protozoans, sperms, ery-

throcytes ets. In 1759 K. F. Wolf started that cells are found in living substances.

Cytology progressed slowly until the beginning of the 19th century, when Amigi designed lenses that corrected the problems of spherical and chromatic ab-

errations that had plagued microscopic investigations until then. This important de-

velopment resulted in en explosion of knowledge, so that within a few years

Robert Brown (1831) discovered the nucleus and showed that it is present in all

cells.

As a result of numerous studies from 1665 to the year 1839 German botanist

Matthias Schleiden and German zoologist Theodor Schwann gave the famous Cell

Theory according to which "The cells are organisms and animals as well plants are

aggregates of these organisms, arranged in accordance with definite laws". Thisled to Virchow's proposal in 1858 that pathological changes were the result of cel-

lular malfunction and to his theory of cell lineage. In 1840 J. E. Purkinje proposed

the name protoplasm for living substance present in a cell. By the last quarter of

the 19th century, the design of microscopes had been improved further; in addition,

dyes developed by organic chemists were now being used in cytological investiga-

tions. These advances allowed cytologists to begin a serious exploration at the sub-

cellular level and resulted in the description of mitosis by Strasburger in 1875

year . In 1875 year Van Beneden observed the centrioles, in 1879 W. Flemming re-

ported the chromatin of the nucleus and used the term mitosis for cell division

in 1882 year .

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The term “cell biology” first appeared in 1876 with the establishment of

the Laboratory of Cell Biology at the Catholic University of Louvain in Belgium.

While these advances in the understanding of the cell were occurring, the sci-

ence of biochemistry was also evolving from organic chemistry. In 1828, Wohler

synthesized urea from inorganic compounds, and the concept of "vital force" in or-

ganic chemistry was abandoned. In 1869, in one of the first experiments Miescher isolated cell nuclei and showed that they contained a complex of protein and a nu-

cleic acid. During the last part of the century there was a systematic application of

the techniques of organic chemistry to the investigation of biological macro-

molecules, especially by Fisher . This eventually led to the understanding of the

structure of proteins, lipids, and nucleic acids.

In 1878 Kuhne introduced the name enzyme but the actual chemical na-

ture of enzymes was not established until more than a century after their discov-

ery. The techniques that led to our current understanding of the structure and

function of cell organelles were not developed until the 1940th in Claude's labo-ratory at the Rockfeller institute. Claude assembled a group of individuals who car-

ried out the first systematic studies in which biochemical analyses of cell frac-

tions were related to morphology.

Ultracentrifugal cell fractionation and electron microscopy, together with pro-

cedures for cell culture, provided the basis for the development of cell biology as

we know it today. Within 20 years of the isolation of microsomes (by Claude in

1938) most cell organelles had been identified and characterized in the electron

microscope. What is now the “Journal of Cell Biology” was founded in 1955 as the

Journal of Biochemical and Biophysical Cytology, and the American Society for

Cell Biology held its first meeting in 1961. During this time our perception of the

cell has changed considerably, and further evolution of our basic concepts can be

expected. Cell biology is not static, and it is important to remember that the re-

search of the next decade can be expected to change some of our views and to ex-

pose as many new problems as it solves.

2.2. Historically important events in Cell Biology.1590 - Jansen invented the compound microscope which combines two lenses for

greater magnification.

1665 - Robert Hooke, using an improved compound microscope, examined cork

and used the term "cell" to describe its basic units.

He thought the cells were empty and the walls were the living material.

1650 - 1700 - Antony van Leeuwenhoek, using a good quality simple lens

(mag. 200) observed nuclei and unicellular organisms including bacteria.

1831 - Robert Brown described the nucleus as a characteristic spherical

body in plant cells.

1838 - Schleiden (a botanist) and Schwann (a zoologist) produced the "cell

theory".

1840 - Purkinje discovered the protoplasm as contents of cells.

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1858 - Virchow showed that all cells arise from the pre-existing by cell division.

Now this idea is the third part of the cell theory.

1866 - 1888 - cell division was studied in detail and chromosomes were described.

1880 - Plastids were discovered.

1890 - Mitochondria were discovered.

1898 - Golgy apparatus was discovered.1930 - Electron microscope was developed.

1946 to present - electron microscope became widely used in biology revealing

march more detailed structure in cells. This "fine" structure is called ultrastructure.

2.3. Cell theoryThe unifying concept that cells are the fundamental units of all living things is

a part of the cell theory. Two German scientists, botanist Matthias Schleiden in

1838 and zoologist Theodor Schwann in 1839, were the first to point out that

plants and animals are composed of group cells and that the cell is the basic unit of living organisms.

The cell theory was extended in 1858 by Rudolph Virchow, who started that

new cells are formed only by the division of previously existing cells. In other

words, cells do not arise by spontaneous generation from non-living matter (an

idea that was rooted in the writings of Aristotle and had persisted over many cen-

turies). About 1880, another famous biologist, August Weismann, pointed out an

important corollary to Virchow’s statement, that all the cells living today can trace

their ancestry back to ancient times. Evidence that all cells living have a common

origin is provided by the basic similarities of their structures and the molecules of which they are made.

Certain changes have been made in the original cell theory on the basis of the

knowledge gained in the 20-th century.

2.4. The classical states of cell theory.1. The basic unit of structure and function of living organisms is cell.

2. All cells are basically alike in chemical composition and metabolic activities.

3. All cells arise from the pre-existing by cell division.

2.5. Modern Cell Theory1. The cell is the fundamental unit of structure and function in living things.

2. All cells are basically alike in chemical composition and metabolic activities.

3. All cells come from pre-existing cells by division.

4. Multicellular organisms compose of many cells which are connect together

and form unique system.

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http://en.wikipedia.org/wiki/Cell_(biology)

http://en.wikipedia.org/wiki/Cell_(biology)



2.6. The types of cells.There is a great variation in the form, size and number of cells present in the

body of living beings. But all the cells found in nature are divided into two inde-

pendent and radically different groups which are as follows:

1. Prokaryotic (pronuclear) type.

These include very minute cells such as bacteria and blue-green algae. These

cells are characterized by the

absence of nucleus and most

of cytoplasmic organelles.

Prokaryotes appeared about

3500 million years ago Eu-

karyotes appeared first in the

late Pre-Cambrian period,about 2000 million years ago,

and probably evolved from

prokaryotes. The genetic ma-

terial (DNA) in prokaryotes is

not enclosed by nuclear mem-

branes, and lies free in the cy-

toplasm (fig. 1-a).

2. Eukaryotic type.

These cells are found in all animals and higher plants, fungi and most of the

algae. They have a distinct nucleus inclosed in nuclear membrane and other char-

acteristics. The cells of eukaryotes (en, true) are much more complex and are char-

acterized by a true nucleus that is genetic material enclosed by membranes (the nu-

clear envelope) to form a definite, easily recognizable structure (fig. 1-b).

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Fig. 1-a. Bacterial cell.

Fig. 1-b. Eukaryotic cell.



2.7. Comparisons of cell organization in prokaryotes and eukaryotes.

Feature Prokaryotes Eukaryotes

Living organisms

Cell size

Form

Genetic material

Nuclear envelope

Chromosomes

Nucleolus

DNA

Organelles:

Cell wall

Ribosomes

Endomembranes

Mitochondria

Chloroplast

Extra-nuclear ge-

netic material

Exocytosis and en-

docytosis

Division

Locomotion

Nitrogen fixation

Bacteria and blue-green algae

Avarage diameter 0.5 – 5 nm

Unicellular or filamentous

Genetic material spread out in the

cytoplasm. Nucleus is absent.

Absent

Single

Absent

Circular without proteins

Rigid and contains polysaccharides

with proteins, fat. Murein is main

strengthening compound.

70S (smaller)

Endoplasmic reticulum and Golgi

body are absent.

Absent (respiratory enzymes on the

surface of plasma membrane)

Absent

Have circular genetic units (DNA)

in the cytoplasm, known as plas-

mids. Plasmids serve as autono-

mous carries of genetic materialfrom one bacterial cell to the other

and often combine with the chro-

mosome of the recipient bacterial

cell.

Absent

Amitosis

Single fibril, flagellum

Some have the ability

All other plants and animals, in-cluding human being.

Upto 40 nm diameter common,

commonly 1000-10000 times vol-

ume of prokaryotic cells.

Unicellular or filamentous or truly

multicellular.

Genetic material concentrated with-

in the nucleus.

Present

Multiple

One or more nucleoli present in nu-

cleus.

Linear, associated with proteins and

RNA to form chromosomes within

a nucleus.

Cell wall of green plants and fungi

rigid and contains polysaccharides.

Cellulose is main strengthening

compound of plant walls, chitin of

fungal walls.80S (larger), ribosomes may be at-

tached to endoplasmic reticulum.

Endoplasmic reticulum and Golgi

body present.

Present

Present in plant cell.

In mitochondria and plastids.

Present

Mitosis and meiosis

Cilia and flagella

None have the ability.

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CHAPTER 3: General plan structure of eukaryotic cell.

3.1. Origin of eukaryotic cell.

The eukaryotic cell seems to have evolved from a symbiotic community of prokaryotic cells. It is almost certain that DNA-bearing organelles like the mito-

chondria and the chloroplasts are what remains of ancient symbiotic oxygen-

breathing proteobacteria and cyanobacteria, respectively, where the rest of the cell

seems to be derived from an ancestral archaean prokaryote cell – a theory termed

the endosymbiotic theory.

There is still considerable debate about whether organelles like the hy-

drogenosome predated the origin of mitochondria, or vice versa: see the hydrogen

hypothesis for the origin of eukaryotic cells.

Sex, as the stereotyped choreography of meiosis and syngamy that persists innearly all extant eukaryotes, may have played a role in the transition from prokary-

otes to eukaryotes. An 'origin of sex as vaccination' theory suggests that the eu-

karyote genome accreted from prokaryan parasite genomes in numerous rounds of

lateral gene transfer. Sex-as-syngamy (fusion sex) arose when infected hosts began

swapping nuclearized genomes containing coevolved, vertically transmitted sym-

bionts that conveyed protection against horizontal infection by more virulent sym-

bionts.

3.2. Subcellular components.

When comparing the organization of E. coli with that of a plant cell or an ani-mal cell, one is struck by the relative complexity of the eukaryotes. In a non-di-

viding eukaryotic cell the nucleus exists as a separate compartment surrounded and

limited by the nuclear envelope. Another and generally larger compartment is rep-

resented by the cytoplasm, and finally there is the cell membrane with its multiple

enfolding and differentiations. Each of these three main components or compart-

ments of the cell (nucleus, plasma membrane and cytoplasm) contain several sub-

components or subcompartments.

PLASMA MEMBRANE.Structure. The structure that separates the cell contents from the external envi-

ronment is the plasma membrane. This is two-layered film (6 to 10 nm thick) made

of molecules of fats pressed between two sets of protein molecules, and is perfo-

rated by small holes. Most cell membranes also contain variable amounts of glyco-

proteins and glycolipids. The plasma membrane can be revolved only with the

electron microscopy, which reveals numerous enfolding and differentiations as

well as the different types of junctions that establish connections with neighboring

cells.

This is three-dimension view of the membrane at the molecular level, in

which the “ fluid mosaic” model is reproduced by Singer and Nicolson in 1972.

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http://en.wikipedia.org/wiki/Symbiosis

http://en.wikipedia.org/wiki/Mitochondria


http://en.wikipedia.org/wiki/Chloroplasts

http://en.wikipedia.org/wiki/Proteobacteria

http://en.wikipedia.org/wiki/Cyanobacteria

http://en.wikipedia.org/wiki/Archaea

http://en.wikipedia.org/wiki/Endosymbiotic_theory

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http://en.wikipedia.org/wiki/Hydrogen_hypothesis


http://en.wikipedia.org/wiki/Symbiosis



http://en.wikipedia.org/wiki/Chloroplasts

http://en.wikipedia.org/wiki/Proteobacteria

http://en.wikipedia.org/wiki/Cyanobacteria

http://en.wikipedia.org/wiki/Archaea

http://en.wikipedia.org/wiki/Endosymbiotic_theory








They observe, that all plasma membranes are composed chiefly of proteins and

lipids, not so much carbocchadrates (in human red cell – 52% of proteins, 40% -

lipids, 8% - carbocchadrates). Lipids are cholesterol, but most of lipids are phos-

phoglycerides. The “head” of such molecules become ionized under pH conditions

commonly found in cell, but “tails” end usually remain uncharged. The polar and

non-polar regions of these molecules react quit differently where placed in water.The polar “head” tend to form hydrogen bonds with water molecules. Consequent-

ly, the charged regions of phosphoglycerides are said to be hydrophilic (“water-

loving”), the uncharged

“tails” are said to be hy-

drophobic (“water-

hating”). The polar

“heads” are in the contact

with intra- and extracellu-

lar aqueous fluids, and thenon-polar “tails” are di-

rected toward the center of

the bilayer, isolated from

water molecules. There are

proteins peripheral and integral , depending on how deeply they penetrate into the

lipid bilayers. Hence, the membrane is highly asymmetrical. The molecular asym-

metry of plasma membrane is further emphasized be the oligosaccharide chain of

glycoproteins and glycolipids that protrude only at the surface of the membrane

(fig. 2).

Properties and f unctions of plasma membrane.

1. Plasma membrane is selectively permeable.

Some substances pass across plasma membranes readily, others move across

slowly only under certain conditions; and still others normally cannot enter cells at

all.

2. Absorption of materials (endocytosis).

Endocytosis and exocytosis are active processes involving the bulk transport

of materials through membranes, either into cells (endocytosis) or out of cells (exo-

cytosis). Endocytosis occurs by an extension of the cell surface membrane to form a

vesicle vacuole. It is two types:

a) Phagocytosis (“cell eating”) – material taken up is in solid form. Cells spe-

cializing in the process are called phagocytes and are said to be phagocytic; for ex-

ample, some blood cells. The sac formed during uptake is called a phagocytic vac-

uole.

b) Pinocytosis (“cell drinking”) – material taken up is in the liquid form (a so-

lution, colloid or fine suspension). Vesicles formed are often extremely small, in

which case the process is known as micropinocytosis and the vesicles as mi-

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Fig. 2. Structure of plasma membrane.



cropinocytotic. Pinocytosis is particularly associated with amoeboid protozoans

and many other, often amoeboid cells, such as leucocytes, embryo cells, liver cells

and certain kidney cells involved in fluid exchange. It can also occur in plant cells.

3. Excretion of materials (exocytosis)

Exocytosis is the reverse process of endocytosis by which materials are re-

moved from cells, such as solid, undigested remains from food vacuoles or reverse pinocytosis in secretion.

4 .Transport of materials (diffusion, active transport, facilitated transport)

5. Locomotory function.

Many cell types are capable of locomotion, forming the locomotion structure-

flagella (protozoa) and cilia (protozoa).

6. Cell form.

NUCLEUS.

Structure. The nucleus is the most important component ("little organ")

of aneukaryotic cell. It contains four main structural elements: double-membranous nu-

clear envelope, nucleolus, nucleoplasm (karyoplasms) and chromatin (fig. 3).

Fig. 3. Structure of nucleus.

The nucleus is bounded by the "double membrane" the so called "nuclear en-

velope". These two tightly attached membranes are of the same basic structure asthe familiar lipid-protein bilayer. Scattered throughout the double membrane nu-

clear envelop are "Nuclear Pores", these are holes or passages through which

large molecules can pass.

There are two major types of material within the nucleus.

1) The "nucleoplasm": the jelly-like matrix within which all other materials

within the nucleus "float".

2) 'Chromatin": this material is easily stained (Hence the name.)

It is composed of DNA and its associated protein histone which form the long

strands called "chromosomes".

13

Nucleoplasm

Nucleolus

Chromatin

Nuclear

envelope



Also found within the nucleus are dark staining parts called "nuceoli" (little

nucleus) which are rich in the other type of nucleic acid RNA (Ribonuelic acid).

The nucteoli have the task of assembling (synthesizing) a special type of RNZ used

to create the ribosomes rRNA (Ribosomal RNA).

Functions:1. To keep the hereditary material and regulates the transmission of it in gen-

erations.

2. To regulate the all metabolic processes in the cell.

3. To synthesize the ribosomes.

CYTOPLASM.

Structure. The protoplasm of a cell laying the plasma membrane but outside

the nucleus is known as cytoplasm. The cytoplasm appears as a structureless fluid

mass. It includes the cell organelles, cytosol and cell inclusions.Functions. It takes in raw materials and energy through its membranes which

serve as conducting channels, and manufactures proteins and enzymes of various

kinds. It is concerned with taking in food and changing it into living parts of a cell.

It forms substances needed by the cell or for export outside the cell into other cells.

The cytoplasm also extracts chemical energy from sugar and fats and transfers it to

the special energy-rich molecules (ATP) which circulate in the cell.

3.3. Eukaryotic organelles.

There are two groups of eukaryotic organelles, such as membranous and non-membranous.

Membranous:

1. Single membranous organelle:

- endoplasmic reticulum;

- Golgy body;

- lysosomes;

- microbodies (peroxisomes);

- vacuoles (in plant cells).

2. Double membranous organelles:- mitochondria;

- plastids.

Non-membranous organelles:

- ribosomes;

- centrosome;

- microtubules;

- microfilaments.

14



Membranous eukaryotic organelles.

Single membranous organelles:

Endoplasmic reticulum.

Structure. The complex of membranes which can form a significant part of thetotal volume of the cytoplasm in certain types of cells is called endoplasmic re-

ticulum (ER).

ER is a single-membrane organelle, visible only in the electron microscopy.

The electron micrograph, it is a maze of parallel internal membranes that encircle

the nucleus and extend into many regions of the cytoplasm of cell.

The membranes of the ER form the framework or the cytoskeleton of the cy-

toplasm. These membranes usually consist of a series of tightly packed and flat-

tened sack-like structures, that form interconnected compartments within the cyto-

plasm. The internal space formed by the membrane sheets is called the ER lumen.In most cells the ER lumen forms a single internal compartment. Evidence also

suggested that the ER membrane is continuous with the outer membrane of the cell

nucleus, so that the compartment formed between the two nuclear membranes is

connected to the ER lumen. The membranes of other organelles are not directly

connected to the ER and appear to form distinct and separate compartments within

the cytoplasm. Between the spaces of the membranes, the cytoplasm has a cyto-

plasmic matrix or ground substance, containing complex enzymes, synthetic prod-

ucts and storage materials. Enzymes catalyze many different types of chemical re-

actions. In some cases, the membranes serve a framework for systems of enzymes

that carry out sequential biochemical reactions. Other ER enzymes are located

within the ER (fig. 4).

Fig. 4. Rough and smoth ER.

The two surfaces of the membrane contain different sets of enzymes and rep-

resent of the cell with different synthetic capabilities. The two distinct regions of

the ER can be seen in electron micrographs. Although these regions have different

15

Rough ER Smoth ER



functions, their membranes are connected and their internal spaces are continuous.

Rough ER has ribosomes attached to it and consequently appears rough in electron

micrographs. One membrane face (the cytosolic side) is studied with dark particles,

the ribosomes, whereas the other membrane face (the lumen side) appears to be

bare. Smooth ER is more tubular in nature and does not have ribosomes bound to

it, so its outer membrane surfaces have a smooth appearance.Functions of the Smooth ER

1. Synthesis and transport of lipids, carbocchadrates and steroids;

2. Smooth ER serves important function by localizing of detoxifying en-

zymes that breakdown chemicals such as carcinogens (cancer – causing

molecules) and convert them to water-soluble products that can be ex-

creted from the body.

Functions of the Rough ER.

1. Synthesis and transport of proteins.

Golgi body

The Golgi body is a single

membranous organelle, is a differ-

entiated portion of the endomem-

brane system of cytoplasm. Firstly,

it was described by an Italian sci-

entist Camillo Golgi in 1898 as

reticular structure in the cytoplasm

of nerve cells. This membranous

component is spatially and tempo-

rally related to the endoplasmic

reticulum on one side and, by way

of secretory vesicles, may fuse

with specific portions of the plasma membrane. Usually, The Golgi body is placed

near the nucleus. It is found in both animal and plant cells.

The Golgi complex in the living cell was difficult to observe with the light

microscope, and this led to many controversies regarding its true nature. The use of

electron microscopy provided a distinct image of this organelle, and its structurecould be studied in detail.

Structure. The Golgi complex is morphologically very similar in both plant

and animal cells. It consists of dictyosome units formed by stacks of 1) flattened

disk-shaped single membrane-bound sacs called cisternae or saccules ; 2) clusters

of tubules and vesicles and 3) lager vacuoles filled with an amorphous or granular

content. The Golgi cisternae are arranged in parallel and are separated by a space

20 to 30 nm, which may contain rod-like elements or fibers. Each dictyosome is a

polarized structure having a proximal or forming face, generally convex and closer

to the nucleus or the ER and distal or maturing face of concave shape that encloses

16

Fig. 5. Golgi body structure.



a region containing large secretory vesicles. At the forming face are vesicles and

tubules that converge, forming a fenestrated plate. The cisternae lack ribosomes

and are surrounded by a zone in which organelles are excluded. However, some

free ribosomes may be at the periphery of the Golgi body (fig. 5).

Functions.

1) The glycosidation of lipids and proteins to produce glycolipids and glycoproteins. The secretory pathway: ER – Golgi complex – secretory granule.

2) The cell secretion of enzymes which help in transferring metabolic and

synthetic products;

3) The formation of primary lysosomes.

Lysosomes.

Lysosomes are single membrane cytoplasmic organelles, that contain numer-

ous (about 50) hydrolytic enzymes and in which the main functions are intracellu-

lar and extracellular digestion. They were first discovered by a Belgian BiochemistChristian De Duve in 1949 and named in 1955. Lysosomes have been found both

in animal and plant cells and in Protozoan. In bacteria there are no lysosomes, but

the so-called periplasmatic space, found between the plasma membrane and the

cell wall, may play role similar to that of the lysosomes.

Structure. Lysosomes are separated as a fraction that is intermediate between

mitochondria and microsomes. The lysosomes are stable in the living cell. The ly-

sosomal enzymes are enclosed within a membrane (accounting for their latency)

and generally act at acid pH.

Lysosomes show considerable polymorphism. The primary lysosomes (stor-

age granules) are dense particles of about 0,4 nm surrounded by a single mem-

brane. The enzymatic content is synthesized by the ribosomes and accumulated in

the ER. From there the enzymes penetrate into the Golgi region and surrounded by

a single membrane, lysosomes are formed. The secondary lysosomes (digestive

vacuoles) result from the association of primary lysosomes with vacuoles contain-

ing phagocytized or pinocytized material. These called heterophagosomes. Residu-

al bodies are formed if the digestion is incomplete. They contain undigested mate-

rial. These structures may be eliminated, but in most cases they remain in the cell

as pigment inclusions and may be related to the aging process. The autophagic

vacuole or cytolysosome is a special case in which parts of the cell are digested.This normal process is stimulated during starvation and by the pancreatic hormone

glucagons.

Lysosomal enzymes are synthesized in the ER and then packaged at the gerl

region of the Golgi complex to form the primary lysosomes. The mechanism of

lysosome formation is yet unknown.

Functions.

1) Digestion of food or various materials taken by phagocytosis or pinocyto-

sis;

17



2) Digestion of parts of the cell and foreign particles by a process called auto-

phagy.

3) Breakdown of extracellular material by the release of enzymes into the sur-

rounding medium;

4) Autolysis of cell.

Microbodies.

Peroxisomes are the organelles rich in peroxidase, catalase, D-amino-acid oxi-

dase, and urate oxidase. They are abundant in the liver, kidney and in many cell

types of animals and plants. They have 0,6- 0,7 nm granules with a single mem-

brane and a dense matrix. The peroxisome is related to the production and decom-

position of H2O2 and to the β-oxidation of fatty acids and play a role in ther-

mogenesis.

In plants, peroxisomes carry out the process of photorespiration, which in-

volves the cooperation of chloroplasts and peroxisomes.Glyoxysomes are special plant organelles involved in the metabolism of stored

lipids (fat metabolism).

Double membranous organelles.

Energy transformation in cells takes place with the intervention of two main

transducing systems (systems that produce energy transformations) represented by

mitochondria and chloroplasts.

Mitochondria.

Mitochondria (GR., mito-, thread+chondrion, granule), are granular or fila-

mentous organelles present in the cytoplasm of all eukaryotic cells (protozoa, ani-

mal and plant cells). They provide an energy-transducing system by which the

chemical energy contained in foods tuffs is converted by oxidative phosphorylation

into high-energy phosphate bonds (ATP).

First observed at the end of the 19th century and described as “bioblasts” by

Altman (1886), these structures were called “mitochondria” by Benda (1897 ). Alt-

man predicted the relationship between mitochondria and cellular oxidation, and

Warburg (1913) observed that respiratory enzymes were associated with cyto-

plasmic particles. In general, they are rod-shaped, with diameter of about 0,5 nm

and variable length that may range up to 7 nm. Mitochondria are, in general, uni-formly distributed throughout the cytoplasm, but there are many exceptions to this

rule. In some cases, they accumulate preferentially around the nucleus or in the pe-

ripheral cytoplasm, during mitosis; mitochondria are concentrated near the spindle.

The distribution of mitochondria within the cytoplasm should be considered in re-

lation to their function as energy suppliers. Their orientation in the cell may be in-

fluenced by the organization of the cytoplasmic matrix and vacuolar system.

The number of mitochondria is also various in different cells (there are 1000

to 1600 mitochondria in a liver cell; 300000 in some oocytes). Green plants con-

tain fewer mitochondria than animal cells.

18



Structure. A mitochondrion consists of two membranes and two compart-

ments. An outer limiting membrane surrounds the mitochondrion. Within this

membrane, and separated from in by a space of about 6 to 8 nm, is an inner mem-

brane that projects into the mitochondrial cavity complex enfolding called mito-

chondrial cristae or crests. This is generally homogeneous, but it may contain a fil-

amentous material or small highly dense granules. The mitochondrial crests are in-complete septa or ridges that do not interrupt the continuity of the inner chamber.

The shape and disposition of these crests vary in different cells and their number is

related to the oxidative activity of the mitochondrion. The outer membrane is

smooth and the inner membrane shows, on its inner surface, particles linked to the

membrane, which contain a

special ATP-ase. Within the

mitochondrial matrix are small

ribosomes and a circular DNA,

different types of RNAs. Thematrix is gel-like and contains

a high concentration of soluble

proteins and smaller molecules.

Thus, mitochondria may syn-

thesize the proteins, lipids.

They are semiautonomous or-

ganelles (fig. 6).

Functions. Mitochondria are the “power house” of a cell, they bring about the

chemical reactions which take place in tissue respiration and they also break down

fats, proteins and carbocchadrates into smaller particles and transfer their chemical

energy into complex energy-rich molecules of adenosine triphosphate (ATP).

Plastids.

Eukaryotic plant cells have specialized organelles – the plastids – which are

double-membranous and contain pigments and may synthesis and accumulate vari-

ous substances.

In 1883 Schimper first used the term “plastid” for special cytoplasmic or-

ganelles present in eukaryotic plant cells. There are three types of plastids: chloro-

plasts, chromoplasts and leucoplasts. Leucoplasts are colorless plastids are found inembryonic and germ cells, also found in meristemic cells and in those regions of

the plant not receiving light. True leucoplasts are found in fully differentiated cells

and never become green. The leucoplasts have also been characterized by the ab-

sence of thylakoids and ribosomes. They are three types: amyloplats produce

starch, proteinoplasts accumulate protein, elaioplasts produce fats and essential

oils.

Chromoplasts are colored plastids that contain less chlorophyll than the

chloroplasts, but more carotenoid pigments, such as lycopene. Some plastids may

store starch and protein at the same time. Yellow or orange chromoplasts occur in

19

Fig. 6. Mitochondria structure.



petals, fruits and roots of certain higher plants. The most important and most com-

mon plastids are the chloroplasts. They are characterized by the presence of pig-

ments such as chlorophyll and carotenoids and by their fundamental role in photo-

synthesis. Chloroplasts are localized mainly in the cells of the leaves of higher

plants and in algae. Their shape, size, number and distribution vary in different

cells but are fairly constant for a given tissue. In higher plants they are discoid. Thesize and number are genetically controlled. Chloroplasts multiply by division, they

are semiautonomous organelles.

Leukoplasts and chromoplasts have the similar structure as chloroplasts.

Structure. Under light microscope, many chloroplasts show small granules,

called grana. There are three main components: the envelope, stroma and thyla-

koids. The envelope is made of a double limiting membrane (outer and inner). The

inner membrane of mature chloroplast is not in continuity with the thylakoids. The

stroma is a gel-fluid phase that contains 50% of the chloroplast proteins. It has ri-

bosomes and DNA. The thylakoids consist of flattened vesicles arranged as a me-mbranous network. The outer surface of

the thylakoid is in contact with the stroma,

and its inner surface encloses an intra thy-

lakoid space. Thylakoids may be stacked

like a pile of coins, forming the grana or

they may be unstacked (stroma

thylakoids), forming a system of anasto-

mosing tubules that are joined to the grana

thylakoids. In thylakoids, chlorophyll,

carotenoid molecules and a reaction center

are assembled forming two photosystems,

which are important for photosynthesis.

Function of chloroplasts: Photosynthesis.

Non - membranous eukaryotic organelles.

Ribosomes.

The ribosome is a non-membranous organelle, spherical particle and is composed of a large and a small subunit. Ribosomes were first observed by Palade in

the electron microscope as dense particles or granules. Ribosomes are found in all

cells and provide a scaffold for the ordered interaction of all molecules involved in

protein synthesis.

Structure. Eukaryotic ribosomes sediment in sucrose gradients with a sedi-

mentation coefficient of 80S (values of the sedimentation coefficients are not addi-

tive because they depend on factors such as the shape of the particles), prokaryotic

ribosomes are smaller and sediment at 70S. Ribosomes are also found in the mito-

chondria and chloroplasts of eukaryotic cells. During protein synthesis several ri-

20

Fig. 7. Chloroplast structure.



bosomes become attached to one m-RNA molecule, forming a polyribosome or

polysome. The major constituents of ribosomes are r-RNA and proteins present in

approximately equal amounts. R-RNA may provide some of the catalytic activities

required for protein synthesis.

Function. Protein synthesis.

Microtubules.

Structure. Microtubules are found in all eukaryotic cells – either free in the

cytoplasm or forming part of centrioles, cilia and flagella. They are tubules 25 nm

in diameter, several micrometers long, and with a wall 6 nm thick with 13 subunits.

the stability of different microtubules varies. Cytoplasmic and spindle micro-

tubules are rather labile, whereas those of cilia and flagella are more resistant to

various treatments. The main component is a protein called tubulin. The assembly

of tubulin in the formation of microtubules is a specifically oriented and pro-

grammed process. Centrioles, basal bodies, and centromeres are sites of orientationfor this assembly (fig. 8).

Functions.

1. They are related to the primitive forms of cell mobility.

2. They play a mechanical function and the shape of the cell and cell proc-

esses is dependent on microtubules (cell differentiation).

3. The polarity and directional gliding of cultured cells depend on micro-

tubules.

4. Associated with transport of molecules, granules and vesicles within the

cell.

5. They play a role in the contraction of the spindle and movement of chro-

mosomes and centrioles.

6. They form the cilia and flagella.

7. They play a role in sensory transduction.

Microfilaments.

Structure. The microfilaments ranging between 5 and 7 nm in width represent

the active or motile part of thecytoskeleton. The contractile

protein actin and myosin, well

as tropomyosin and other pro-

teins found in muscle, are

present in microfilaments (fig.

8).

Function: They play the major

role in cyclosis and amoeboid

motion.

21

Fig. 8. Cytoskeleton.



Centrosome (cell center, centrosphere).

Lying near the nucleus is a small clear area of cytoplasm free from granules, it

is known as centrosomes. The centrosome is extanuclear and firmly attached to the

nuclear envelope. The centrosome’s position often determines the polarity of the

cell, with the cell axis passing through it and the nucleus. The centrosome containsa minute dot-like centriole, at the end of interphase, two pairs of centrioles exist.

The centriole as microtubular organelle has a triplet organization (nine triplets of

microtubules). The centrosome is typically only for animal cell, in plant cells are

absent (fig. 9).

Functions:

1. They play a role in forming the spindle

during nuclear division.

2. They play a role in intracellular trans-

port.3. They play a role in cytoskeleton forma-

tion.

CHAPTER 4: CHEMICAL COMPOSITION OF CELL.Living things get their energy from the sun directly or indirectly but they get

their living matter from the earth. Organisms are maid from the same materials

that make up the rest of the world. The living matter (substance), first studied andnamed "sarcode" by Dujardin in 1841, is called protoplasm. This is the physical

and biological basis of life and carries on the characteristic life activities of an or-

ganism. The sarcode was renamed protoplasm by a Czech Physiologist Purkinje

in 1842.

Although protoplasm is made up of several elements, yet it is not a com-

pound but a mixture of a number of chemical compounds. Its exact chemical anal-

ysis has not been made.

4.1. Chemical elements.

Protoplasm contains more than 80 elements from 106 of periodical system of

D. I. Mendeleyev which are found when the protoplasm of a variety of living

things is analyzed. Among these only 12 elements are universally present of which

carbon (C), oxygen (O), hydrogen (H) and nitrogen (N) are the most important.

Calcium (Ca), sodium (Na), potassium (K), sulphur (S), phosphorus (P), iron (Fe),

magnesium (Mg) and chlorine (Cl) are less common.

Earl Freidan in 1972 found four more elements present in the living matter.

These are fluorine (F), silicon (Si), tin (Sn) and vanadium (Va). Carbon (C), hy-

drogen (H), oxygen (O) and nitrogen (N) make up about 95% of protoplasm in

which there is about 62% oxygen, 20% carbon, 10% hydrogen and 3% nitrogen.

22

Fig. 9. Centrosome structure.



The other elements are about 5%, they occur in fractions of less than 1%, but the

small quantity of an element may be vital: iron in red blood corpuscles, phosphorus

in nerve and reproductive cells.

4.2. Chemical compounds.

Elements do not exist as such but are combined to form organic and inor-ganic compounds and water. Protoplasm contains hundreds of different kinds of

organic constituents in the form of proteins, lipids, carbohydrates and nucleic ac-

ids. Organic compounds form the organic basis of living matter, they constitute

about 30-40% of protoplasm. The inorganic compounds are water, gases and inor-

ganic salts which comprise about 60-70% of protoplasm.

4.3. Characteristics of main structural components of protoplasm.

ORGANIC COMPOUNDS a) Proteins.

They are quite abundant and constitute the framework of protoplasm, they are

found only in protoplasm and nowhere else in nature. Proteins form about 16% of

protoplasm. Proteins are made up of 20 known amino acids which contain carbon

(C), hydrogen (H), oxygen (O), nitrogen (N), and traces of sulphur (S), phospho-

rus (P), magnesium (Mg) and iron (Fe). Protein molecules are very large contain-

ing thousands of atoms, they coagulate on heating. Proteins are broken down into

amino acids which serve as bricks for building up protoplasm. The cells constantly

make new proteins from amino acids. Common proteins are white of an egg (albu-men), myosin of meat, and hemoglobin of food.

b) Carbohydrates.

They constitute about 13% of protoplasm. They are made up of carbon (C),

hydrogen (H) and oxygen (O), in which hydrogen (H) and oxygen (O) are in the

same proportion as in a molecule of water (H2O). Common carbohydrates are

starch and sugar. When carbohydrates are broken down, they form glucose which

is a source of energy. In animals glucose is reserved for supplying energy when

needed. Plants can form several carbohydrates from CO2 and H2O in the presence

of sunlight (carbon assimilation).c) Lipids or Fats.

Fats and fat-like substances are called lipids. They are found in small quan-

tities, except in special cells where fats are abundant. They are formed of carbon

(C), hydrogen (H) and oxygen (O), but the amount of oxygen is small, they are of-

ten associated with phosphates and sulphates. Lipids are insoluble in water but are

soluble in organic solvents like benzene and petrol. Lipids are broken down into

fatty acids and glycerols, and they also supply some energy. They exist as stored

food material as lard and oil, they also form wax, pigment, bite acids and sex hor-

mones. Fats form the framework of bounding membranes of cells. Thus they

control the movements of substances in or out of protoplasm. Fats and carbohy-

23



drates can change into each other. Carbohydrates and fats do not coagulate on

heating.

d) Enzymes.

Enzymes are complex proteins, they are organic catalysts which bring about

chemical reactions with great rapidly, but they themselves remain unchanged. En-

zymes are destroyed on heating. The exact chemical nature of many enzymes is notknown, but they are like complex proteins. They are found only in the living pro-

toplasm and are present in very large numbers. A single cell may have over a thou-

sand different kinds of enzymes, some of which are secreted into the digestive tract

and in the blood stream. Enzymes used in the digestion of food are called hy-

drolytic enzymes. A number of enzymes bring about the release of chemical en-

ergy from the food; these are collectively known as respiratory enzymes. Every

single reaction in the protoplasm is not without the activity of some enzyme. Some

well-known enzymes are pepsin, lipase, amylase, trypsin, carbonic anhydrose, de-

hydrogenases and ribonuclease.e) Nucleic acids.

They are the fundamental substances of protoplasm, nucleus, nucleolus and

chromosomes. Nucleic acids are the most complex and the largest known organic

molecules. A nucleic acid is composed of smaller units called nucleotides. A nu-

cleotide itself is composed of sugar, phosphoric acid and some nitrogenous basis.

Two of the nucleic acids are very important : a) deoxyribonucleic acid (DNA in

short is a part of the nuclear material, and b) ribonucleic acid (RNA) is found

in the cytoplasm as well where it takes an active part in the synthesis of proteins.

f) Regulatory substances.

There are additional substances which direct the activities of cells or control

the functions of the animal. These regulatory substances are hormones, vitamins

and respiratory pigments. Hormones are secretions of ductless glands, they regu-

late metabolism and control growth. Vitamins are complex organic parts of food,

they are essential for normal growth, maintenance of health, and a full utilization

of food, their absence causes some disease. Respiratory pigments such as hemoglo-

bin, take up oxygen (O2) and remove carbon dioxide (CO2) from protoplasm during

respiration, some others oxidize glucose to produce energy.

INORGANIC COMPOUNDS a) Water.

Protoplasm contains varying quantities of water in different parts; there is

about 60-90% of water in the protoplasm of different animals. Specialized tissues

in a particular animal vary widely in water content. In man, for example, gray

matter of brain contains about 84%, liver and muscle-tissue - 73-76%, adipose

tissue - 10-30% and dentine of teeth - 10%. In a given animal species, the water

content is the highest in its embryo and decreases with age.

An adult man needs about 3 liters and a cow about 100 liters per day. Water is a

natural solvent and it dissolves more substances than any other liquid, thus en-

24



abling chemical reactions to take place speedily. Water has a high surface tension

which gives the protoplasm a consistency. As free water, it acts as a medium of

dispersion of substances in the protoplasm. However, a large part of water is

bound to colloidal particles in the protoplasm, and this bound condition shows en-

tirely different properties from the free water. Bound water does not freeze into

ice. It is a dispensable in metabolism because enzymes act exclusively in the pres-ence of water. It has a high specific heat; consequently it affords protection against

sudden temperature changes in living organisms.

b) Inorganic salts.

Inorganic salts are chlorides, phosphates, carbonates, bicarbonates and sul-

phates of sodium (Na), potassium (K), calcium (Ca), magnesium (Mg) and iron

(Fe). They constitute 1-4% of protoplasm.

They regulate metabolism and maintain proteins in solution. Calcium and phos-

phorus are necessary for the skeleton; sulphur is found in protein compounds; so-dium and potassium are abundant in blood; magnesium is needed for bone forma-

tion; iron is a necessary part of blood, and chlorine is abundant in blood and

tissue fluids. Most of the inorganic salts are in solution, either free or combined

with organic compounds.

c) Gases.

These are carbon dioxide (CO2) and oxygen (O2), the latter is used by proto-

plasm during respiration and the resultant carbooxygen (CO2) is formed as a waste

product.

Content of chemicals in living and non-living substances.Elements Organization of human being, % Non-living things, %

O

C

H

N

P

K

Na

S

CaMg

Cl

Fe

Zn

Cu

I

F

62.0

21.0

10.0

1.5-3.0

1.0

0.23

0.08

0.16

2.00.03

0.1

0.01

0.0003

0.0002

0.0001

0.0001

49.0

0.35

1.0

0.004

0.12

2.3

2.4

0.1

3.22.3

0.2

3.8

0.005

0.002

0.0005

0.02

According to the dependence of percentage in living cells elements are di-vided into macro-, micro- and ultramicroelements.

25



Macroelements are contained in quantities, exceeding 0,1% (O, C, N, H, P,

S, Ca, Na, K, Cl).

Microelements are contained in organism in the concentration of 0,001-

0, 00001% (Cu, I, F, Br).

Ultramicroelements are contained in quantities less than 0,00001% (Au, Hg

and others).

4.4. Functions of compounds in living organisms.WATER. Biological role of water is determined by polarity of its molecules.

1. Water is solvent and medium for chemical reactions.

2. Water takes place in reactions of intracellular metabolism.

3. Owing to the large thermal capacity it is good thermoregulator.

4. Interacting with protein molecules it determines their chemical struc-

ture, colloidal condition of cytoplasm.

INORGANIC SALTS.1 1. They take part in bimolecular, determining their activity.

2. They support acid-alkaline balance.

3. They play building role.

PROTEINS .

1. Building function.

2. Enzymatic function (proteins-enzymes).

3. Transport function (hemoglobin, ATP-ase and so on).

4. Receptor function (rhodopsin).

5. Protective function (antibodies, interferons).6. Hormone function (insulin, somatotropin, thyrotropic hormone -

polypeptide; vasopressin - 9 amino acids, oxytocin - 9 amino acids; adrenocor-

ticotrop(h)in - 39 amino acids.

7. Motive function (myosin, tubulin and so on).

8. Storing function (egg albumen).

9. Toxins (snake poison - 60-74 amino acids).

10. Antibiotics (cyclosporine, actinimycin).

11. Energy function.

CARBOHYDRATES .

1. Structural function (keratin, ossein, cellulose of cell wall and so on).

2. Storing function (glycogen, starch).

3. Energy function.

LIPIDS.

1. Structural function (cell membranes and organelle membranes).

2. Hormone function (steroids).

3. Storing function (hypodermic fat tissue).

4. Energy function.

5. Vitamins (vit. D; carotenoids).

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Practice 1 Cellular Biology

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