TABLE OF CONTENTS
INTRODUCTION – What is Science?
PART 1 –BIOLOGY
Text 1. What is biology?
Branches of biology
Grammar – Part 1
Word Formation
Prefixes
Suffixes
Text 2. The Human Body
The skeleton
The muscular system
The nervous system
The cardiovascular system
The respiratory system
The digestive system
The integumentary system
The senses
Grammar – Part 2
Order of the affirmative sentence
Punctuation
Text 3. Cells, DNA and Biotechnology
Cells
DNA
Principles of biotechnology
Text 4. Bacteria and Viruses
The lymphatic and immunity system
Metabolism
Infectious diseases and diseases of metabolism
Text 5. Tools of the biologist
Grammar – Part 3
Countable, uncountable and mass nouns
Text 6. Botany Basics
External plant parts
Internal plant parts
Plant life cycles
Plant hormones and growth regulators
Other Readings
Text 7. Bring on the T cells
Text 8. The Killer mutant just got meaner
Text 9. Diseases: what to do
Text 10. Skin so fixed
Text 11. The market for human tissues in the biotechnology age
1
Introduction
What is Science?
Since 1991, the person shown on the £20 note has been the scientist Michael Faraday. He was born
in 1791 and was the son of a blacksmith. He began work as a bookbinder covering books but when he
was 22, he attended the lectures of the great scientist Sir Humphrey Davy.
He was so fascinated by these lectures, that he wrote detailed notes of them. Later, he wrote up the
notes and bound them into books; then he presented the books to Davy. The Royal Institution needed a
laboratory assistant. The young Michael Faraday showed all the care ad thoroughness they were
looking for.
He gave the same care and attention to the observations of a candle. He carefully studied how a candle
burned and he wrote a whole book on what he observed. He also gave lectures on these observations.
What Faraday did was to look carefully at something that everybody else took for granted. He made
careful observations.
Making observations is a vital step towards being a good scientist. Your observations can lead you to
make a guess. You may guess at what you think is happening.
Another name for a guess based on information is a hypothesis. You can test your hypothesis. Your
test can be called an investigation or an experiment. Often your observation will lead you to make a
prediction. A prediction is more than a guess; it’s your statement based on close and careful
observations.
For example, in 1834 Mary Somerville made a prediction. She made careful observations and
calculations on the ways that planets moved. They convinced her that there was another undiscovered
planet beyond the planet Uranus and it was true. Some years later an astronomer at the Berlin
Observatory discovered Neptune.
A scientific method requires some skills that you have to follow:
1.
You predict
2.
You plan and design an experiment
3.
You observe and measure
4.
You interpret and infer. To infer is to draw conclusions.
5.
You evaluate in order to determine that a theory is correct.
6.
You must recognize and control all the possible variables, if you are going to design a fair
test
Parts of an experiment
Variables:
Hypothesis:
Constants:
Control:
Trials:
characteristics in an experiment that change or could be changed.
Independent variable: variable you change on purpose; also called manipulated
variable
Dependent variable: variable that responds to a change in the independent variable;
also called responding variable
educated guess about how changing the independent variable will
affect the dependent variable
characteristics in an experiment that are kept unchanged in all trials.
standard for comparison in an experiment
number of times an experiment is repeated for each level, or value,
of the independent variable. The more trials, the more reliable your results.
Exercise. Complete the following statements.
1.
Looking at something carefully is ________________.
2.
A guess based on information is ___________________.
3.
A test of your hypothesis can be called an experiment or ___________________.
4.
Parts of an experiment that remain unchanged are called _________________.
5.
_______________ ________________ are the ones you change on purpose.
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Text 1.
What Is Biology?
Biology is the science of living things - plants and animals. Sometimes it is easy to tell a living thing
from a non-living thing. The biologist (a scientist who studies living things) knows that a bird and a
tree are alive. He also knows that a rock and a piece of metal are not alive. But there may be close
resemblances between some living things and some non-living things.
For example, the virus that causes a disease of tobacco plants may be just a large molecule. Yet this
virus can reproduce its own kind, which no non-living thing can do.
Living things also can do many other things that non-living things cannot do. They take in food and
nourish themselves. they eliminate waste products. They respond to heat, cold, light, darkness, and
other stimulation. Many living things cannot move about as they choose. Some can even replace worn
out parts of themselves. They do this by a process called “regeneration”.
The outstanding characteristic of living things is that they can make life. A plant takes water and gases
from the air and joins them with mineral solutions that it absorbs through its roots. From this mixture
it makes the living substance of itself. An animal eats plants and other animals and turns this food into
living animal material. All life on earth is produced by other existing life.
Living things are made up of tiny units called cells. Many simple plants and animals, and all bacteria,
consist only of one cell. Many biologists consider bacteria as plants, but some classify them as neither
plants nor animals.
All the living parts of cells contain large molecules called “proteins”. There are thousands of kinds of
proteins in each cell. The proteins form jellies of varying stiffness. This mixture of living jellies was
once thought to be a simple substance that biologists called protoplasm.
Almost all living things that can be seen with the unaided eye are composed of thousands, or even
millions, of cells. Groups of similar cells form tissues. Tissues group together to form organs. Organs
include the brain and heart of an animal, and the roots of a plant. A group of organs that work together
is called a system. In animals, some organs form a circulatory system that circulate the blood. Other
systems take care of such functions as breathing, reproduction, or moving about. In plants, the
vascular system, a network of branching tube-like cells, circulates water from the roots to the other
parts of the plant. The whole plant or animal, made up of cells, tissues, organs, and systems, is called
an organism.
The World Book Encyclopedia
Exercise. Complete the following sentences.
1. Regeneration is a process ______________________________________.
2. _____________________________ is the outstanding characteristic of living things.
3. From the mixture _______________________ a plant ______________________.
4. Cells are ______________________________ .
5. Many biologists ______________________________ some ___________________.
6. Proteins are ________________________________ .
7. Protoplasm is _______________________________.
Branches of biology
Biology is an extensive science encompassing many life science disciplines that can be divided into
distinct areas: match the area to its definition.
a. Energetics
1. studies plants and plant life cycles.
b. Zoology
2. studies animals and their life histories.
c. Botany
3. deals with the way living things function.
d. Paleontology
4. is the science of classification.
e. Embryology
5. explains the roles of elements, compounds and ions in the
fundamental biochemical processes of cells.
f. Ecology
6. explains the vital energy transformations that take place in living
cells.
g.Physiology
7. is the study of structure. It is divided into anatomy (the study of gross
structure), histology (the study of microscopic structure), cytology
(the study of cells).
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h. Molecular biology
i. Taxonomy
j. Evolution
k. Genetics
l. Morphology
8. studies embryo development in plants and animals.
9. explains heredity and variation in living things.
10. determines the possible origins and relationships of living things and
analyzes the changes that occur in species.
11. studies ancient life through examination of fossil records.
12. studies the relationships of plants and animals to one another and to
their physical environment.
Grammar – Part 1
Word Formation
Compound words
Compound words are very common in scientific language. They can be adjectives or nouns. They
come from the combination of various elements.
Possible combinations are:
a. adjective/adverb + past participle
short-sighted
well-dressed
b. number + noun
second-hand
first-rate
c. number + noun +adjective
18-year-old
6-foot-tall
d. noun + noun
bus station
teacup
Compound words can be written:
a. with a hyphen
self-control
b. separately, as 2 words
television set
c. as one single word
toothbrush
There are no strict rules although usually:
a. compound adjectives are written with a hyphen
home-made
well-done
b. compound nouns can be written as 2 words when
exercise book
tomato soup
the first word has the function of identifying the
school bag
spring balance
second one, which does not change its original
meaning
c. compound nouns are written as one word when
postman
boyfriend
the “new word” has its own specific meaning
headache
seafood
Match the words in the two columns creating new words
1. evening
a. book
2. math
b. classes
3. telephone
c. room
4. car
d. sick
5. house
e. teacher
6. bed
f. holiday
7. home
g. park
8. summer
h. box
9. note
i. work
Prefixes:
Negative or opposite:
aan- de- dis-
il-
im-
in-
ir-
non-
un-
_____ adultered ____aerobic _____agree _____approval _____believable _____ efficient
_____exhaustible _____legal _____measurable _____polluted _____ regular _____ motivate
Too much, above:
over-
hyper-
overcooked
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hyperactive
Too little, below: under- hypo- subVery small: microVery large: mega-
underweight
microscope
megabyte
Over a long distance: tele-
hyposomnia
subway
In favor of: pro- pro-peace
Against:
anti-, contraanti-semetic contradict
telescope
Before: pre- foreAfter: post-
pre-read foresee
post-date
Again: reWrongly: mis-
rebuild
misunderstand
Half: semi- semi-detached
Two: bibilingual
Exercise. Create new words by adding prefixes to the following bases.
1. _____ possible
2. _____ happy
3. _____ national
4. _____ paid
5. _____ play
6. _____ arrange
7. _____ fabricated
8. _____ sleep
9. _____moral
Suffixes
-ive, -able,-ic/ical, -atic, -y, -al, -ar, -some, -ly
sugary
circular
transforms nouns into adjectives:
lovable
expensive
-ful:
with, full of
hopeful
careful
-less:
without
hopeless
careless
-ish:
negative quality, nationality
childish
Danish
driver
dentist
accountant
employee
productivity
happiness
-er, -ist, -ee, -ian, ant, -ent : indicates what people do
-ity , -ness, -ship: transforms adjectives into nouns
librarian
leadership
-ly:
transforms adjectives into adverbs
quickly
happily
movement
adaption
repetition
adoption
decision
arrival behaviour
-ment, -ation, -tion, -ion, -sion, -our:
transforms verbs into nouns
Exercise. Turn the following nouns into adjectives by adding a suffix.
1. success ______
2. sulphur _____
3. supplement _____
4. system _____
5. virus _____
6. technology _____
7. water _____
8. trouble _____
9. wealth ____
10. world _____
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Text 2.
THE HUMAN BODY
The Skeleton
The skeleton is the framework of the human anatomy, supporting the body and protecting its internal
organs. Two hundred and six bones compose the skeleton, about half of which are in the hands and
feet. Most of the bones are connected to other bones at flexible joints, which lend the framework a
high degree of flexibility. Only one bone, the hyoid, is not directly connected to another bone in such
an articulation. It anchors the tongue and is attached to the styloid processes of the skull by ligament.
The skeletons of male and female bodies are essentially the same, with the only noteworthy exceptions
being that female bones are usually lighter and thinner than male bones, and the female pelvis is
shallower and wider than the male's.
This latter difference makes childbirth
easier.
Exercise. Match the names with the main
bones of the human body.
Shinbone
Humerus
Clavicle
Mandible
Skull
Ribs
Breastbone
Spine
Metacarpus
Tarsus
Fibula
Radius
Carpus
Thighbone
Shoulder blade
Metatarsus
Phalanges
Kneecap
Ulna
Pelvic Arch
The Muscular system
The human body contains more than 650
individual muscles anchored to the
skeleton, which provide pulling power so
that you can move around.
These
muscles constitute about 40% of your
total body weight. The muscle's points
of attachment to bones or other muscles
are designated as origin or insertion. The point of origin is the point of attachment to the bone to
which the muscle is anchored. The point of insertion is the point of attachment to the bone the muscle
moves. Generally, the muscles are attached by tough fibrous structures called tendons. These
attachments bridge one or more joints and the result of muscle contraction is movement of these joints.
The body is moved primarily by muscle groups, not by individual muscles. These groups of muscles
power all actions ranging from the threading of a needle to the lifting of heavy weights.
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The Nervous System
The nervous system of the human anatomy is responsible for sending, receiving, and processing nerve
impulses. All of the body's muscles and organs rely upon these nerve impulses to function. Three
systems work together to carry out the mission of the nervous system: the central, the peripheral, and
the autonomic nervous systems. The central nervous system is responsible for issuing nerve impulses
and analyzing sensory data, and includes the brain and spinal cord. The peripheral nervous system is
responsible for carrying nerve impulses to and from the body's many structures, and includes the many
craniospinal nerves which branch off of the brain and spinal cord. The autonomic nervous system is
composed of the sympathetic and parasympathetic systems and is responsible for regulating and
coordinating the functions of vital structures in the body.
Of all of these components, the brain is the primary component of the nervous system. It is protected
by the skull and is immersed in the cerebrospinal fluid which helps to absorb external shocks. The
brain is divided into three main areas, the forebrain also called the cerebrum, the mid-brain which
contains cells used in eye movements and the hindbrain which is called the cerebellum. The cerebrum
corresponds to various functions such as interpretations of signals from the senses(sensory) or the
commands sent to voluntarily move muscles(motor). Speech and memory are examples. Voluntary
actions involve thought using the forebrain. The consequent movement is controlled by the
cerebellum. The brain is also divided into two hemispheres, the right and the left. The right side
controls the more creative of our activities while the left side is usually dominant and controls logic
and speech.
The Cardiovascular System
At the centre of the cardiovascular system is the heart which acts as a pump. It is enclosed in a
membrane or sack called the pericardium. The heart has two chambers on each side, the upper atrium
and the lower ventricle. These chambers of contract and relax approximately 70 times a minute to
make the blood flow around the body. In order to stop blood flowing in the opposite direction there are
a series of valves. The bicuspid valve prevents back flow into the left atrium ( whereas the tricuspid
valve prevents back flow into the right atrium. The blood flows away from the left ventricle via the
aorta to the arteries reaching all tissues of the body including bones. Arteries branch into smaller
arterioles which connect to a network of fine capillaries. The deoxygenated blood is carried back to
the heart via the veins to the vena cava from where it enters the right side of the heart. The pulmonary
vein carries the blood to the left side.
Blood
A fresh blood supply is essential to all tissues of the body including bones and its interruption may
cause permanent damage to certain parts of the body such as the brain. Blood consists of plasma, a
watery fluid in which the various particles flow. In this fluid there are dissolved salts, fats, sugars,
proteins and hormones. There are billions of red blood cells called erythrocytes, white blood cells
called leucocytes and phagocytes plus fragments of cells called platelets. Oxygen combines with
haemoglobin in red blood cells to give it its red colour. Oxygenated blood in the arteries is thus a rich
red colour whereas the blood in the veins is bluer.
Red blood cells have an inherited chemical identity that is the basis for blood groups. There are four
main blood groups: A, B, AB. and 0. The identifying protein on the surface of certain types of red
blood cells is called antigen. There are three alleles determining the presence or absence of these
antigens. Allele A which causes antigen A to be formed, allele B which causes antigen B to be formed,
allele O which causes no antigen to be formed. A and B are co-dominant with each other; O is
recessive to both.
Blood plasma may contain special sorts of antibodies called agglutinogens because they cause foreign
blood to coagulate or agglutinate. In blood transfusions, care has to be taken to ensure that blood from
the donor is compatible with that of the recipient so that coagulation will not occur. Note that blood
group AB is a universal recipient, while group O is a universal donor.
When some part of body tissue is damaged, a clot of blood is formed to stop bleeding. The damaged
area releases chemicals which attract platelets. These stick together to form a fibrin web, thus clotting
the blood. When the clot dries, it forms a scab which protects the healing wound.
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The Respiratory System
Oxygen is vitally necessary for our survival. We inhale air through the nostrils of the nose and through
the mouth. The fine hairs in the nose help to filter dirt and dust preventing them from entering the
lungs. From the nose it passes through the pharynx at the back of the mouth, along the throat, to the
larynx. The larynx prevents food from entering the trachea or windpipe leading to the lungs but it also
contains the vocal chords, even though it is not an organ specialized for speech. Many animals with a
larger larynx than man are mute and even when the larynx is removed, patients can learn to speak by
dilating the upper part of the esophagus. The child's larynx shows no difference between the sexes but
during adolescence the female larynx grows very little, whereas the male larynx becomes much more
enlarged, especially the part called the thyroid cartilage which forms the laryngeal prominence or
Adam's apple.
Below the larynx is the trachea, a flexible tube about 10 cm long and 2.5 cm wide. It is strengthened
by between sixteen to twenty tracheal cartilages often called rings but shaped like horse-shoes, open at
the back. It descends with a slight inclination to the right and divides into two main branches, the right
and left main bronchi which then divide into a web of small bronchioles in the lungs.
The right and left lungs are two conical sponge-like air-sacs. They are supported below by the
diaphragm. A thin membrane called the pleura covers the lungs. It is smooth and moist and reduces
friction during breathing. Air enters the minute spaces in the lungs called alveoli where the oxygen is
absorbed by the blood and carbon dioxide is released to be breathed out. When inhaling (breathing in)
the diaphragm and intercostal muscles contract lifting the ribs upwards and outwards so that air enters
the enlarged space of the lungs. When exhaling (breathing out), the diaphragm and ribs relax, pressure
on the lungs increases and air is forced out.
The Digestive System
The digestive system is responsible for processing food, breaking it down into usable proteins,
carbohydrates, minerals, fats, and other substances, and introducing these into the bloodstream so that
they can be used by the body. The digestive, or alimentary, tract begins at the mouth, where the teeth
and tongue begin the breakdown of food, aided by saliva secreted by the salivary glands. The chewed
food, combined with saliva, is swallowed, carrying it in peristaltic (contractile) waves down the
esophagus to the stomach. In the stomach, the food combines with hydrochloric acid which further
assists in breaking it down. When the food is thoroughly digested, the fluid remaining, called chyme,
is passed through the pylorus sphincter to the small intestine and large intestines. Within the long,
convoluted intestinal canals, the nutrients are absorbed from the chyme into the bloodstream, leaving
the unusable residue. This residue passes through the colon (where most of the water is absorbed into
the bloodstream) and into the rectum where it is stored prior to excretion. This solid waste, called
feces, is compacted together and, upon excretion, passes through the anal canal and the anus. Along
the way through the digestive tract, the pancreas, spleen, liver, and gallbladder secrete enzymes which
aid in the digestive process.
The Integumentary System
Skin
Skin, hair and nails protect the body. The outer layer of skin is called the epidermis of which the most
external is dead tissue. This is waterproof and helps to keep out disease. It is, however, sensitive to
touch, heat, cold and pain.
The deeper layers are grouped together under the name of the dermis. Sebaceous glands, sudoriferous
or sweat glands, hair follicles and nail beds are rooted in the epidermis. Sebaceous glands excrete a
fatty substance called sebum which greases the body. Their distribution varies from part of the body to
another. They are more heavily concentrated in the scalp, face and chin, while their absence from the
palms of the hands and the sole of the feet may cause the skin to become too soft after long
immersions in water.
Nails
Nails act as a shield for the tips of the fingers and toes. Keratin is the hard, fibrous protein which
forms the nails and is produced at their base.
8
Hair
Hair helps to keep the body warm and protects most areas of the skin. There are about 100,000 hair
follicles on the head. When it is cold, small muscles push the hairs of the body upright thus helping to
trap air and increase insulation.
The Senses
Hearing
The ear is divided into the inner ear, the middle ear and the outer ear. The inner ear collects the
vibrations arriving from the outer ear and hair-like cells which sense these vibrations, transform them
into electrical impulses which travel along nerves to the brain.
Sight
The sense of sight is one of the most important. Light passes through the cornea and enters the eye
through the hole at the centre of the iris or diaphragm. It then passes through the lens behind to be
projected as an upside-down image on the retina. Here the light stimulates the light sensitive cells
called rods and cones. The rods are very sensitive to movement and even to a very dim light but
perceive only black and white. The cones are less sensitive to light but perceive colour. These signals
are then transmitted via the optic nerve to the brain.
Taste
The tongue is a muscular structure which besides moving food around in the mouth contains taste
buds. They are to be found on small nodules called papillae on the surface of the tongue. They are
grouped into four areas which detect four basic tastes: sour, sweet, salty and bitter.
The taste buds of the tongue work together with the sense of smell to recognise the taste of food and
drink.
Smell
The nose detects smells from substances which have emitted molecules into the air. These molecules
dissolve in the mucus generated in the nose and a system of nerve endings similar to small hairs
transmit signals to the brain. There only we get the smell.
Touch
As a sense organ which responds to touch the skin is the body’s largest organ, having a surface area of
as much as 2 square metres. Although the outer layer of the epidermis is made of dead tissue, it is
sensitive to various stimuli, such as touch, heat, cold and pain.
Exercise. Say if the following sentences are true or false, then correct the false ones making them true.
1. _____ Muscles constitute about 50% of our total body weight.
2. _____ Our body moves primarily by individual muscles.
3. _____ The brain is the primary component of the nervous system.
4. _____ The brain may be divided into three main areas.
5. _____ Ventricles stop blood from flowing in the opposite direction.
6. _____ Blood is redder in the veins than in the arteries because it is oxygenated.
7. _____ Without a larynx, a person cannot speak.
8. _____ The lungs are conical sponge-like air sacs.
9. _____ The respiratory system is responsible for processing food.
10. _____ We have no sweat glands on our scalp or face.
11. _____ Our most important sense is touch.
12. _____ We need cones in order to perceive color.
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Grammar – Part 2
Sentence Order
The affirmative sentence
SVOMPT = subject + verb +object + way/means (modo/mezzo) +place + time
The boy rode his bike quickly along the road at night.
Exceptions:
the object can be separated from the verb if it is very long
Verbs of movement are followed by their destination (I went to Milan by train)
Time and sometimes place can be placed at the beginning
(Outside, the crowd was screaming)
When there is more than one expression of place or time, the one that specifies more
comes first (Let’s meet at six o’clock on Friday )
The negative sentence
Subject + auxiliary + negation + verb
Jimmy does not go to school on Saturdays.
The interrogative sentence
Auxiliary or modal + subject + verb
Can you help me with my luggage?
The interrogative-negative sentence
Auxiliary or modal + subject + negation + verb
Don’t you live in Pavia?
Question words…. Always come first
When it is the subject: Who came yesterday?
When it is object:
Who did you see yesterday?
Which students failed?
Which book do you want?
Questions with hope, believe, suppose, think, imagine, expect, guess, to be afraid:
Is he going to come soon?
I hope so
( spero di si)
I think so
(penso di si)
I suppose so (suppongo di si)
I am afraid so ( ho paura di si, temo di si)
Negatives have two possible constructions
I suppose not
I don’t suppose so
I think not (little used) I don’t think so.
I believe not.
I don’t believe so.
With hope and to be afraid only
I hope not
I’m afraid not.
Exercise. Put the words in the right order to form a sentence.
1. Tea / do / very much / I / like / not.
2. Spends / most of the year / at the seaside / she.
3. The job offers / every day / Jane / in the newspaper / look at / does?
4. In London / late / Charles / arrived / last night.
5. Went / we / skiing / last month / twice.
6. His degree / got / Robert / at Essex University / in 1984 / in Business.
Double object
When a verb (like send and give) has two objects, there are two possibilities:
The indirect object precedes the direct one – Give me the book!
The direct object precedes the indirect one – Give the book to me
When the direct object precedes, the indirect object needs the preposition to.
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If the objects are both pronouns, the direct object always precedes the indirect one.
( not … give me it…. But give it to me)
Exercise. Change the order of the direct and indirect objects in the sentences below.
1. Will you please show me that book?
2. Why don’t you tell the truth to Lisa?
3. Please take this report to Charles.
4. Remember to give me the car keys.
5. Don’t promise the moon to me.
Punctuation marks
A sentence can end with one of these marks:
Full stop (period) .
question mark ?
exclamation mark !
Two sentences can be divided by a:
semi-colon ;
2 separate sentences that are linked in meaning
colon :
before a list or an explanation
comma ,
between items in a list; to show a pause in a long sentence ; when you
want to add extra information.
hyphen to join two words together; to show that a word has been divided and continues on the next line.
dash which is informal and is used instead of a colon or a semi-colon
“quotation marks” to show the words are spoken; to show that someone else originally
wrote the words
apostrophe’
for missing letters; for possessions
capital letters
the first letter of a sentence; for countries, nationalities, languages,
religions, names of people, events, organizations, trademarks, days,
months, titles; for titles of books, films, etc.; for abbreviations.
Exercise. Put the correct punctuation in the paragraphs below.
1. tribes have lived in the rainforests of south america for over 10000 years people like these have the
oldest cultures on earth but now they are in serious danger when columbus sailed to the americas 500
years ago between six million and nine million people lived in the amazon rainforest today that
number is less than 200000 since 1900 87 tribes have disappeared completely why because outsiders
shot them poisoned them and gave them diseases
2. according to an arabic legend one day a caravan travelling along the route to bagdad met the plague
the head of the caravan was surprised to see her there so he asked her why are you running to bagdad
the plague looked him firmly in the eye for awhile then answered to take five thousand lives when the
califs were returning to their home town a month later they met the plague again this time the great
calif told her you lied to us you said you were taking five thousand lives and yet i saw at least fifty
thousand victims in bagdad i never tell a lie the plague answered five thousand lives i took and not one
more it was fear who killed the others
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Text 3.
Cells, DNA and Biotechnology
Cells
Cells were discovered by the help of the microscope in the 17th century but it wasn’t until the 19th
century that it was realized that they were the building blocks of all plant and animal life. The cell is
the smallest unit of living matter which can have and independent existence. It is the simplest of
organisms and may consist of one cell only (e.g. amoeba). It measures between 10 and 100 microns.
Cells are usually generated by dividing themselves, but sometimes, as in the case of sexual
reproduction, by fusion. There are two main types of cell: bacteria cells which have no nucleus and
few inner structures or animal and plant cells which have a nucleus and are more complex.
Parts of a cell
The nucleus, at the center of the
cell, contains the DNA.
Cytoplasm is a gelatinous substance
consisting of approximately 70%
water where food is stored and the
chemical reactions of the cell’s
metabolism take place.
Protoplasm is the contents of the
cell, i.e. the nucleus and cytoplasm.
The Golgi body stores and packages
substances made by the cell and
transports them to the cell’s surface.
The cell membrane surrounds the protoplasm and controls the flow of substances entering or leaving
the cell.
The cell wall is an external layer covering the membrane. It makes the plant cell keep its shape.
Vacuoles are spaces containing liquid (sap in plants). Large in plants but very small or non existent in
animal cells. The cell wall in plants is reinforced with a thick layer of cellulose and inside the cell
there are chloroplasts which hold the chlorophyll.
Key functions of cells
Digestion: chemical decomposition of food, etc. by enzymes.
Secretion: release of substances synthesized by the cell or of waste products.
Transport: movement in and out of substances through the cell membranes.
Absorption: use of digested substances creating the materials needed for cell life.
Reaction to Stimuli: controlled response activated by other cells or the environment.
Reproduction or Mutation: division into two cells with the new cell having inherited the genetic
characteristics of the original one.
Energy Transformation: in plants photosynthesis, i.e. the absorption of light energy to transform
carbon dioxide into organic matter in the presence of chlorophyll.
Movement: ability of the cell to change its position in relation to other cells.
Synthesis: production of substances such as proteins, lipids, carbohydrates controlled by enzymes.
DNA
DNA stands for deoxyribonucleic acid. DNA is found in chromosomes. It is one of the most important
kinds of molecules found in living things. DNA contains instructions which decide which proteins a
cell will make. This determines the whole chemistry of the cell.
DNA molecules are made up of two long chains of smaller molecules, called nucleotides. So DNA is a
polynucleotide. The two chains of nucleotides wind round one another in a helix. The shape of a DNA
molecule is a double helix.
There are four different kinds of nucleotides (also called bases) in a DNA molecule. The are Adenine),
Thymine, Cytosine and Guanine (usually abbreviated A, T, C, and G, respectively). The nucleotides
can be arranged in any order along one of the DNA strands. The order of the nucleotides determines
the kinds of proteins which the cell will make.
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Proteins are chains of amino acids. There are about 20 kinds of amino acids. The sequence of these
different amino acids in a protein chain determines what kind of protein it is. Keratin, for example, has
a completely different sequence of amino acids from hemoglobin.
Your cells make thousands of different proteins. They make them by stringing amino acids together in
particular orders. The instructions for doing this come from your DNA molecules. A part of a DNA
molecule which gives instructions for making one kind of protein is called a gene.
DNA does this by carrying the instructions in the form of a code, called the genetic code. The code is
a “three-letter” code. The letters are the nucleotides on one of the DNA strands in the double helix. A
row of three nucleotides is a “code-word”, which stands for a particular amino acid.
Although the DNA of all organisms uses these same bases, differences in the sequence of bases
account for differences between species and even between individuals of the same species. Differences
in base sequence account for all the genetic differences between living things. The DNA of identical
twins is identical, but the DNA of fraternal twins differs as much as that of brothers and sisters.
It is the presence or absence of a specific protein that gives an organism a particular trait. As DNA is
passed from one generation to the next, so are specific genes, allowing us to “inherit” traits from our
parents. Throughout the history of life on Earth, genes have carried information from one generation
to the next. Genes are the fundamental drivers of evolution. Over millions of years, the evolution of
complex organisms - plants, animals, and humans - was achieved through the transfer, deletion, and
mutation of genes. Without genetic variability, evolution could not occur, and the world would be
devoid of most, if not all, life. In a sense, every organism on Earth is the product of genetic
engineering by nature. Each of us is in fact the product of a genetic-engineering experiment performed
by our ancestors. The same is true for other animals, plants and microbes. These natural mechanisms
for genetic change allow an organism to gain new traits, and they drive evolution. Biotechnology, both
traditional and modern, simply takes advantage of these natural genetic phenomena to produce useful
organisms and products from these organisms.
Principles of Biotechnology
Biotechnology defined
Biotechnology can be broadly defined as “using living organisms or their products for commercial
purposes”. As such, biotechnology has been practised by human society since the beginning of
recorded history in such activities as baking bread, brewing alcoholic beverages, or breeding food
crops or domestic animals.
A narrower and more specific definition of biotechnology is “the commercial application of living
organisms or their products, which involves the deliberate manipulation of their DNA molecules”.
This definition implies a set of laboratory techniques developed within the last 20 years.
Principles of Biotechnology
Except for the sequence and number of letters in each gene, the DNA from any organism is chemically
and physically the same. One of the greatest scientific discoveries of biotechnology is that DNA from
any organism will function if it is transferred into any other organism.
Using Biotechnology to Modify Plants and Animals
Sexual reproduction can occur only between individuals of the same species. A Holstein cow can be
mated with a Hereford bull because the two animals are different breeds of the same species, cattle.
But trying to mate a cow with a horse, a different species of animal, would not be successful. What's
new today is that scientists have been able to identify the specific DNA genes for many desirable traits
and transfer only those genes, usually carried on a plasmid or virus, into another organism. This
process is called genetic engineering and the transfer of DNA is accomplished using either direct
injection or Agrobacterium electroporation, or particle gun transformation techniques. It provides a
method to transfer DNA between any living cells (plant, animal, insect., bacterial, etc.) Virtually any
desirable trait found in nature can, in principle, be transferred into any chosen organism. An organism
modified by genetic engineering is called transgenic.
Products of Genetic Engineering
Genetic engineering is being used in the production of pharmaceuticals, gene therapy, and the
development of transgenic plants and animals..
Pharmaceuticals. Human drugs such as insulin for diabetics, growth hormone for individuals with
pituitary dwarfism, and tissue plasminogen activator for heart attack victims, as well as animal drugs,
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are being produced by the fermentation of transgenic bacteria that have received the appropriate
human, cow, or pig gene..
Gene Therapy. The first clinical gene therapy is underway to correct an enzyme deficiency called
ADA in children. Bone marrow cells are removed, defective DNA in bone marrow cells is
supplemented with a copy of normal DNA, and the repaired cells are then returned to the patient's
body.
Transgenic Plants. Transgenic plants that. are more tolerant of herbicides, resistant to insect or viral
pests, or express modified versions of fruit or flowers have been grown and tested in outdoor test plots
since 1987. The genes for these traits have been delivered to the plants from other unrelated plants,
bacteria, or viruses by genetic engineering techniques.
Transgenic Animals. Presently, most transgenic animals are designed to assist researchers in the
diagnosis and treatment of human diseases.
Using Biotechnology in Diagnostic Applications
Since each living creature is unique, each has a unique DNA recipe. Individuals within any given
species, breed, or hybrid line can usually be identified by minor differences in their DNA sequencesas few as one difference in a million letters can be detected.
Using the techniques of DNA fingerprinting, scientists can diagnose viral, bacterial, or fungal
infections, distinguish between closely related individuals, or map the locations of specific genes
along the vast length of the DNA molecules in the cells.
Diagnosing Infectious Diseases and Genetic Disorders
Diagnosis of infectious diseases is a profound application of the new DNA technology.
Tuberculosis, AIDS, and many other infectious diseases, in addition to the inherited disorders like
cystic fibrosis or sickle cell anaemia, are diagnosed within hours by the PCR technique rather than
days or weeks by traditional methods. The greatly increased sensitivity and speed, as compared with
traditional methods, allow earlier intervention and treatment.
Identifying Organisms
By using RFLP technology, DNA fingerprints can be generated. Any individual organism can be
uniquely identified by its DNA fingerprint. Consequently, this fingerprint can be used to determine
family relationships in paternity litigation, match organ donors with recipients in transplant programs,
connect suspects with DNA evidence left at the scene of a crime (in the form of hair or body fluids), or
serve as a pedigree for seed or livestock breeds.
DNA profiling
DNA profiling is based on the discovery that the DNA of one person differs from that of another in
specific ways. The FBI analyses 13 places on a person's DNA to produce a DNA profile and find
whether it matches that of a known criminal. Here are the steps in the process.
Collection: blood, semen, saliva, skin or hair is labelled and shipped to a forensic lab. Only minute
amounts - a single hair root, for example - are required.
Isolation: the sample is mixed with detergent and enzymes, which break open the cells and let out their
DNA. The cell fragments are removed, and the remaining mixture is spun in a centrifuge tube. That
makes pure DNA settle to the bottom.
Amplification: the DNA, a double helix, is separated into two strands. Technicians add 26 short pieces
of DNA, called primers: sequences of the chemicals C, A, T and G that link to the beginning and end
of each of the 13 sites.
Replication: when a primer attaches to the beginning of one of the 13 sites, it acts like the "start"
button on a photocopying machine, turning on cellular machinery that makes million copies or more of
each site.
Identification: copies of the 13 sites, each about 100 to 600 chemical letters long, are separated by
size through gel electrophoresis. In this process a drop containing millions of DNA fragments is
placed at one end of a sheet of gel. Electric current pulls the fragments across the gel; the larger a
fragment, the slower it moves. The fragments, tagged with dye, show up as colored bands under
ultraviolet light.
Matching: the crime lab feeds the data on the length of the 13 markers into a database. The computer
searches for a match. The odds are trillions to one that the length of each of the 13 strands in one
person is identical to all the lengths in another.
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Exercise. Multiple choice. Choose the best word(s) to finish the sentences.
1. The contents of a cell is called __________________
a. nucleus
b. cytoplasm
c. protoplasm
d) all of the above
2. The absorption of light energy transforming CO2 into organic matter is called ____________
a. reaction to stimuli
b. digestion
c. energy synthesis
d. photosynthesis
3. DNA molecules are composed of 2 chains of smaller molecules called ______________
a. bases
b. chromosomes
c. proteins
d. polynucleotides
4. The part of DNA which gives instructions for making a protein is the ______________
a. genetic code
b. gene
c. amino acid
d. nucleotide
5. Evolution has been achieved through the transfer, deletion and ______________ of genes.
a. inheritance
b. absence
c. addition
d. mutation
6. Sexual reproduction may take place only between individuals of the same _____________
a. breed
b. species
c. family
d. none of the above.
7. An organism modified by Genetic Engineering is called ______________
a. mutant
b. clone
c. transgenic
d. transformed
8. Insulin is a drug used in the cure of
a. heart disease
b. diabetes
c. dwarfism
d. all of the above
9. Discovering that the DNA of one person differs in specific ways from that of another has been
the basis for
a. DNA fingerprinting b. DNA profiling
c. DNA matching
d. all of the above
10. The odds that the length of each of the 13 strand in one person is identical to all 13 lengths in
another are
a. thousands to one
b. millions to one
c. billions to one
d. trillions to one
Text 4.
Bacteria and Viruses
Bacteria are unicellular organisms. They normally reproduce themselves by binary fission. This can
happen as rapidly as three times an hour, which means that one bacterium can multiply to 16 million
in 24 hours. Bacteria have a large loop of DNA, called bacterial chromosome. Plasmids attached to
bacteria act like parasites but carry spare genetic information and can help the bacterium to resist
antibiotics and other threats. This is why bacteria have developed resistance to treatment.
Some bacteria, however, are useful to the human organism in combating harmful ones. For example,
lactic acid bacteria helps to defeat the spread of salmonella. Yoghurt is a dairy product made from
milk fermented by bacteria and is beneficial in maintaining the balance of useful bacteria in the
intestines.
A virus is an infective and disease-producing agent which is made up of a core of nucleic acid
enclosed in a protein covering. Viruses are not cells and can only reproduce by entering a living cell.
The human body combats viruses by producing an antiviral protein, interferon, which stops the spread
of the infection. Retroviruses have an RNA genome and can produce DNA from this RNA.
Drugs to fight viruses are difficult to develop because viruses use the genetic mechanism of host cells
which may be damaged by the same drug. Another problem is that some viruses gradually develop
resistance to the few antiviral drugs which have been proved safe to use. There is a difference in the
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way bacteria and viruses cause disease. Bacteria damage the organism's cells whereas viruses damage
the organism by producing other viruses.
The Lymphatic and Immunity System
The body defends itself against infection by producing cells and chemicals which combat germs. The
skin also acts as a barrier against unwanted bacteria.
The immune cells circulate the whole body but are more abundantly present in the lymphatic tissues.
Fluid from the blood passes into the tissues of the body and is then returned to the lymphatic system to
be filtered before returning once again to the bloodstream. Immune cells protect against invasion by
bacteria, viruses and other foreign bodies such as transplanted tissues and some poisons. They
recognise cells from the same body because of the personal characteristics of their membranes.
Foreign cells, including infected and cancerous ones, are destroyed.
There are four main types of immune cells. Neutrophils are about 60% of white blood cells. They can
surround and isolate invading organisms. This phenomenon is known as phagocytosis. Macrophagus
cells search for and destroy foreign bodies and waste. B lymphocyte cells make specific antibodies
ready to recognise and destroy specific invaders. T lymphocyte cells control antibody production by B
cells and eliminate infected cells.
Active immunization protects the body for long periods of time, often for life, by injecting vaccine
which copies the infection in a harmless form. This vaccine stimulates the production of antibodies.
Passive immunization is the injection of antibodies from the blood of donors who have recently
suffered from the disease. It gives only short term protection.
Metabolism
Metabolism is the term for all the chemical reactions which take place in the cells of living organisms.
All the energy used by living things depends on a cycle which derives from the sun’s energy, either
directly, as in the case of plants which absorb this energy and produce food by photosynthesis, or
indirectly, as in the case of animals that receive this energy consuming food originally derived from
plants.
There are two kinds of metabolism in the human body, catabolism and anabolism.
Catabolism is the breaking down of complex molecules of food into simpler ones to produce energy.
This energy heats the body and maintains the main functions such as muscular and nervous activity.
Anabolism is the essential process of building and replacing tissue cells which is a necessary and
continuous process. Without these constant processes of metabolism, a living thing would die.
The BMR or basal metabolic rate is the speed of metabolism of an organism in a state or rest. This rate
varies according to age, sex and weight. It is controlled by the hormone thyroxine which is produced
by the thyroid gland. The BMR can be tested. If it is high this may be caused by an over-active
thyroid gland. A person with a high BMR is usually over-active, thin, anxious and nervous. A person
with a low BMR is usually overweight, tired and slow in his movements. Drugs my be used to correct
these conditions. Barbiturates decrease the BMR while amphetamines increase it.
Infectious Diseases and Diseases of Metabolism
AIDS is caused by a retrovirus called human immunodeficiency virus (HIV). A retrovirus contains the
genetic material RNA instead of DNA like other viruses. The virus is transmitted in the body fluids,
mainly blood and sexual secretions. Having the virus does not mean that one is suffering from AIDS.
Only half of the people with the virus develop the disease within ten years. It causes death as the body
no longer has immunity against other diseases, so that even a minor illness can be fatal.
Chicken Pox is mainly suffered by children under ten. Symptoms include a high temperature and spots
which later become blisters.
Measles is an acute viral disease spread by the air. The symptoms are fever, catarrh and a red rash
which lasts about a week following two weeks of incubation.
Smallpox is a highly contagious viral disease which is often fatal. The symptoms include aching, fever,
vomiting, and skin eruptions which lead to scars. Vaccination, first developed by Edward Jenner in
about 1800 has helped to reduce the dangerous impact of the disease but in .countries where vaccines
are scarce it can still be a severe threat to life.
Scarlet fever or scarlatina is an acute infectious disease which mainly occurs in children. Symptoms
are a sore throat and a red rash spreading down the body. The affected skin later peels off.
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Mumps is a virus infection with fever and swelling of the parotid salivary glands, especially those
below the ears. It may be considered a mild form of meningitis when suffered by children but it may
be very severe in adults. There is an effective vaccine MMR usually given to children at the age of 18
months.
Whooping Cough is an acute infectious disease caused by the bacterium Bordella pertussis which is
carried by the air into the respiratory tract. It may cause a high temperature, loss of appetite, vomiting
and nose-bleeds but the main symptom is severe coughing with the characteristic 'whoop' or sound of a
rapid intake of breath.
Exercise. Which diseases have you had?
I’ve had it once
I’ve had it more
than once
I’ve been
vaccinated against
chicken-pox
cholera
common cold
diphtheria
flu
german measles/rubella
hepatitis
measles
mumps
polio
rabies
tetanus
tuberculosis
typhus
whooping cough
yellow fever
other
Text 5.
The Tools of the Biologist
The modern biologist requires the use of some very special tools and laboratory techniques that enable
him/her to perceive, measure and record data precisely.
Measurement is a basic requirement of all research. Modern instruments of measurement permit
astounding degrees of numerical precision. Biometrics is the science that combines mathematics and
statistics needed to deal with the facts and figures of biology. Computers aid the investigator's tasks by
accepting massive quantities of numerical data and making calculations at very high speed.
The laboratory or field scientist derives numerical data from using all kinds of measuring instruments
designed for remarkable precision. Weighing in micro quantities requires the use of an analytical
balance. The manometer measures the uptake of gases involved in cellular respiration and
photosynthesis. Spectrophotometers are able to measure differences in densities of fluids by colour
comparisons not discernible to the human eye. Radioactivity is located and measured by the Geiger
counter, a machine structured to feed pulses of electricity into an electronic counter. Scintillation
counters measure light flashes imperceptible to the eye while ultraviolet rays are used to measure very
thin objects.
Discovery in biology involves the ability to take apart the substances of cells so that the secrets of their
biochemical processes can be exposed. The technique of chromatography permits the biologist to
separate very small quantities of a substance into its component parts. Electrophoresis is a technique
17
that uses electrical charges to separate the amino acids in proteins. A biologist studying cell processes
wishes to isolate the organelles, or parts within the cell unit. When tissue and loosening fluid are
placed into a test-tube-like device and spun in a centrifuge, the membrane enclosing the cells will split
open. Based on weight differences, the organelles of each cell fall to the bottom of the tube at each
successive spin of the centrifuge. A number of techniques and instruments have helped scientists to
see things better. X-ray diffraction is a procedure by which X-rays sent through a crystal reveal the
pattern of molecules and atoms contained in the crystal. This technique was used to determine the
structure of the hereditary material DNA. All sorts of microscopes have extended the investigators'
field of vision. The best light microscope is capable of magnifying objects 2,000 times. The phase
contrast microscope makes transparent specimen visible, while the dark-field or the ultra-microscope
gives vivid clarity to fragile and transparent organisms. The ultraviolet microscope is used for
photographing living bacteria and naturally fluorescent substances. The electron microscope is capable
of magnifying objects more than 200,000 times. Using electrons instead of light and magnets in place
of lenses, the electron microscope has revolutionized the study of the cell. The scanning microscope
has improved upon the resolution of fine detail made possible by electron microscopy.
This is only a small sampling of the kinds of tools and techniques available to the modem biologist.
There are incubators for temperature control, refrigerators for keeping things cool, auto analysers for
separating and classifying the elements in the blood, automatic mixers and stirrers and shakers, pH
meters, autoclaves for sterilizing, timers and machines that measure time to the fraction of a second.
Exercise. Complete the following statements.
1. The _____________ balance weighs micro quantities of substances.
2. The ______________ measures the uptake of gases in cellular respiration and photosynthesis.
3. Spectrometers ________________________________________________________.
4. ________________________ permits to separate very small quantities of a substance into its
component parts.
5. _______________________ separates the amino acids in proteins.
6. Scintillation counters __________________________________________________.
7. A centrifuge _________________________________________________________.
8. _________________ reveals the pattern of molecules and atoms in a crystal.
Grammar – Part 3
Countable, Uncountable and Mass Nouns
Countable nouns: any noun you can count: ex. Apple, tree, dog etc.
Uncountable nouns: (like Italian)
a. substances ex. Gold, bread, butter, cheese, sand
b. abstract nouns ex. Weather, violence, courage, justice
c. nouns ending in –ing ex. Handwriting, parking, camping (activities not places)
carpark campsite
d. to make them countable we use: a bar of, a piece of, a slice of, a loaf of, a spoon of, a
tube of , a jar of, a can of, a pinch of, a grain of, a cup of, etc.
e. sometimes we can use I’d like two coffees and a beer (sottointeso cups or glasses)
f. nouns that are countable in Italian but not in English: advice, business, damage,
furniture, hair, information, luggage/baggage, money, news, work
/homework/housework (countable job), permission (countable permit), progress,
research, equipment, laughter (laugh). To talk about one we say a piece of, a type of,
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an item of ,etc. 1) never use a/an 2) never plural 3) use some, any, no, a lot, lots of,
not much, little + verb in singular form
Mass nouns: people, police, and cattle are always plural:
audience, crowd, family, government, orchestra, staff, team are usually singular but can be plural – it
depends on whether we consider the group as a whole or the individuals
Attention:
1. some nouns have both singular and plural forms with a difference in meaning; e.g. pain,
damage, saving, hair, property, work, and business
2. some nouns have a plural form (with s) but take a singular verb; e.g. mathematics, economics,
gymnastics, linguistics
3. some nouns have the same singular and plural forms (with s or without s) and so they can take
singular or plural verbs accordingly; e.g. crossroads, series, species, means, headquarters,
aircraft, sheep, salmon, deer
4. some nouns are plural and require a plural verb but they cannot take a number; e.g.
belongings, arms, earnings, goods, outskirts.
Exercise - is or are?
1. This orchestra _____ the biggest in the world.
2. The police _______ always in search of criminals.
3. My trousers _____ a bit large.
4. These species of insects _______ rare.
5. This news _______ good.
6. How much luggage _________ there?
Text 6.
Botany Basics
Plants are essential to life on Earth. Either directly or indirectly, they are the primary food source for
humans and other animals. Additionally, they provide fuel, replenish the earth’s oxygen supply,
prevent soil erosion, slow down wind movement, cool the atmosphere, provide wildlife habitat, supply
medicinal compounds and beautify our surroundings.
Many plants are familiar to us, and we can identify and appreciate them based on their external
structures. However, their internal structures and functions often are overlooked. Understanding how
plants grow and develop help us capitalize on their usefulness.
Photosynthesis
One of the major differences between plants and animals is the plants’ ability to manufacture their
own food. This process is called photosynthesis, which literally means “to put together with light”. To
produce food, a plant requires energy from the sun, carbon dioxide from the air and water from the
soil. During photosynthesis, it splits carbon dioxide into carbon and oxygen, adds water, and forms
carbohydrates (starches and sugars). Oxygen is a by-product.
The formula for photosynthesis can be written as follows:
Carbon dioxide + Water + Sunlight = Sugar + Oxygen
or
CO2 + 6 H2O + Energy => C6H12O6 + 6 O2
After producing carbohydrates, a plant either uses them as energy, stores them, or builds them into
complex energy compounds such as oils and proteins. All of these food products are called
photosynthates. The plant uses them when light is limited, or transports them to its roots or developing
fruits.
19
Photosynthesis occurs only in the mesophyll layers of plant leaves and, in some instances, in
mesophyll cells in the stem. Mesophyll cells are sandwiched between the leaf’s upper and lower
epidermis and contain numerous chloroplasts, where photosynthesis takes place. Chloroplasts are
incredibly small. One square millimetre, about the size of a period on a page, would contain 400,000
chloroplasts.
Chlorophyll, the pigment that makes leaves green, is found in the chloroplasts. It is responsible for
trapping light energy from the sun. Often chloroplasts are arranged perpendicular to incoming sun rays
so they can absorb maximum sunlight. If any of the ingredients for photosynthesis – light, water, and
carbon dioxide - is lacking, photosynthesis stops. If any factor is absent for a long period of time, a
plant will die.
External plant parts
External plant structures such as leaves, stems, roots,
flowers, fruits, and seeds are known as plant organs. Each
organ is an organized group of tissues that works together
to perform a specific function. These structures can be
divided into two groups: sexual reproduction and
vegetative.
Sexual reproduction parts produce seed; they include
flower buds, flowers, fruit and seeds.
Vegetative parts include roots stems, shoot buds and
leaves; they are not directly involved in sexual
reproduction. Vegetative parts often are used in asexual
forms of reproduction such as cuttings, budding, or
grafting.
Internal plant parts
Cells are the basic structural and physiological units of
plants. Most plant reactions (cell division, photosynthesis,
respiration, etc) occur at the cellular level. Plant tissues,
such as meristems (growing points), xylem (waterconducting tissue), phloem (photosynthate-conducting
tissue), are large, organized groups of similar cells that
work together to perform a specific function.
A unique feature of plant cells is that they are readily totipotent. In other words, almost all plant cells
retain all of the genetic information (encoded in DNA) necessary to develop into a complex plant. This
characteristic is the main reason that vegetative (asexual) reproduction works. For example, the cells
of a small leaf cutting from an African violet have all the genetic information necessary to generate a
root system, stems, more leaves, and ultimately, flowers.
Specialized groups of cells called meristems are a plant’s growing points. Meristems are the site of
rapid, almost continuous cell division. These cells either continue to divide or begin to differentiate
into other tissues and organs. How they divide, and whether they ultimately become a tissue or an
organ, is controlled by a complex array of internal plant hormones but also can be influenced by
environmental conditions. In many cases, you can manipulate meristems to make a plant do something
you want, such as change its growth pattern, flower, alter its branching habit, or produce vegetative
growth.
Exercise. Answer the following questions.
1. How are plants important to us?
2. What is photosynthesis?
3. What does a plant do with the sugars and starches it produces?
4. What are photosynthates?
5. Where does photosynthesis take place?
6. What is chlorophyll and why is it important to plants?
20
7. What two groups can the external plant parts be divided into? What parts are in each group?
8. What do we mean when we say a plant is totipotent? Why is it important?
9. What are meristems? Why do we manipulate them?
Plant Life Cycles
Based on its life cycle, a plant is classified as an annual, a biennial, or a perennial.
An annual, such as a zinnia, completes its life cycle in one year. Annuals are said to grow from seed to
seed in one year or growing season. During this period, they grow, mature, bloom, produce seeds and
die. There are both winter and summer annual weeds, and understanding a weed’s life cycle is
important in controlling it. Summer annuals complete their life cycle during spring and summer; most
winter annuals complete their growing season during fall and winter.
A biennial requires all or part of two years to complete its life cycle. During the first season, it roduces
vegetative structures (leaves) and food storage organs. The plant overwinters and then produces
flowers, fruit, and seeds during its second season. Swiss chard, carrots, beets, and parsley are example
of biennials.
Sometimes biennials go from seed germination to seed production in only one growing season. This
situation occurs when extreme environmental conditions, such as drought or temperature variation,
cause the plant to pass rapidly through the equivalent of two growing seasons. This phenomenon is
referred to as bolting. Sometimes bolting occurs when biennial plant starts are exposed to a cold spell
before being planted in the garden.
Perennial plants live more than two years and are grouped into two categories: herbaceous perennials
and woody perennials.
Herbaceous perennials have soft, non-woody stems that generally die back to the ground each winter.
New stems grow from the plant’s crown each spring. Trees and shrubs, on the other hand, have woody
stems that withstand cold winter temperatures. They are referred to as woody perennials.
Plant hormones and growth regulators
Plant hormones and growth regulators are chemical that affect flowering; aging; root growth;
distortion and killing of leaves, stems, and other parts; prevention or promotion of stem elongation;
color enhancement of fruit; prevention of leafing and/or leaf fall; and many other conditions. Very
small concentrations of these substance produce major growth changes.
Hormones are produced naturally by plants, while growth regulators are applied to plants by humans.
Plant growth regulators may be synthetic compounds that mimic naturally occurring plant hormones,
or they may be natural hormones that were extracted from plant tissue
Applied concentrations of these substances usually are measured in parts per million (ppm) or in some
cases parts per billion (ppb). These growth-regulating substances most often are applied as a spray to
foliage or as a liquid drench to soil around a plant’s base. Generally, their effects are short-lived, and
they may need to be reapplied in order to achieve the desired effect.
There are 5 groups of plant-growth-regulating compounds: auxin, gibberellin (GA), cytokinin,
ethylene, and abscisic acid (ABA). For the most part, each group contains both naturally occurring
hormones and synthetic substances.
Auxin causes several responses in plants:
 Bending toward a light source (phototropism)
 Downward root growth in response to gravity (geotropism)
 Promotion of apical dominance (the apical bud suppresses growth of buds below it on the
stem)
 Flower formation
 Fruit set and growth
Auxin is the active ingredient in most rooting compounds in which cuttings are dipped during
vegetative propagation.
Gibberellins stimulate cell division and elongation, break seed dormancy, and speed germination. The
seeds of some species are difficult to germinate; you can soak them in a GA solution to get them
started.
21
Unlike other hormones, cytokinins are found in both plants and animals. They stimulate cell division
and are often included in the sterile media used for growing plants from tissue culture. If a medium’s
mix of growth-regulating compound is high in cytokinins and low in auxin, the tissue culture explant
(small plant part) will produce numerous shoots. On the other hand, if the mix has a high ration of
auxin to cytokinin, the explant will produce more roots. Cytokinins also are used to delay aging and
death (senescence).
Ethylene is unique in that it is found only in the gaseous form. It induces ripening, causes leaves to
droop (epinasty) and drop (abscission), and promotes senescence. Plants often increase ethylene
production in response to stress, and ethylene is often found in high concentrations within cells at the
end of a plant’s life. The increased ethylene in leaf tissue in the fall is part of the reason leaves fall off
trees. Ethylene is also used to ripen fruit (e.g. green bananas).
Abscisic acid is a general plant-growth inhibitor. It induces dormancy and prevents seeds from
germinating; causes abscission of leaves, fruits, and flowers; causes stomata (tiny openings in the
epidermis that allow H2O, O2 and CO2 to pass into and out of a plant) to close. High concentrations of
ABA in guard cells during periods of drought stress probably play a role in stomatal closure.
Exercise. Decide if the following statements are true or false and then correct the false ones.
1. _____ An annual completes its life cycle in two years.
2. _____ Understanding the life cycle of a weed helps us keep it under control.
3. _____ Bolting happens when biennials are forced to go through two growing seasons in one.
4. _____ Perennials can be divided into three groups; herbaceous, trees and shrubs.
5. _____ Plant hormones can produce major changes using minor quantities.
6. _____ Hormones are applied to plants by humans while growth regulators are produced
naturally by the plant.
7. _____ Usually, growth regulators need to be applied only once to achieve the desired effect.
8. _____ Gibberellins are often used to on seeds that are difficult to sprout.
9. _____ Auxins differ from the other hormones in that they are also found in animals, not only
in plants.
10. _____ Ethylene, which is only present in a liquid form, is used to ripen fruit.
Other Readings
Text 7.
Bring on the T Cells
A highly experimental treatment has dramatically shrunk deadly skin cancers in several patients, all by
knocking out natural immune cells to make way for an army of tumoral-attacking cells.
Only 13 people have had the treatment so far and it hasn’t worked for all of them. But it is already
attracting attention as a potential approach against infectious diseases such as AIDS as well as cancer.
The treatment takes advantage of a subset of T cells, a major part of our immune system, which can
recognise proteins that are common in tumour cells. These T cells provide a natural protection against
cancer. But if a tumour is too aggressive the body can't make enough of them to cope.
In the past scientists have tried multiplying a patient's own in anticancer T cells in the lab and then
injecting them back in. But the cells decreased in just a few days.
Steven Rosenberg's team at the National Cancer Institute in Maryland have now conquered this
problem, using hints from mouse experiments. Before putting the T cells back into patients, the team
depleted the normal reservoir of immune cells through chemotherapy, making room for the new T
cells.
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The tumours shrank in 6 of 13 patients with metastatic melanoma, an aggressive form of skin cancer.
"The first patient, treated in September 2000, is still disease-free", says Rosenberg. The anti-cancer T
cells stuck so well that, in two patients, they peaked at more than 90 per cent of their total T-cell
count.
"That's remarkable", says Rosenberg. They usually only make up about 1 per cent.
Other patients weren't as lucky - the new T cells didn't take and their cancers didn't shrink. Rosenberg
is now trying to figure out why. Some users developed side effects such as loss of skin pigment or
inflammation in the eye. "For tumours like melanoma, where the autoimmune reaction is usually not
life threatening, that seems like a good trade off", says Gregory Plautz of the Cleveland Clinic of
Ohio.
Sylvia Pagan Westphal in «New Scientist», October 17, 2002
Exercise. Answer the following questions.
1. What are T cells?
2. How can they be a natural protection against cancer?
3. What experiment was carried out in Maryland?
4. What were the results of the experiment?
5. Were there any side effects?
Text 8.
The Killer Mutant Just Got Meaner
Make sure you don’t bring a nasty souvenir back from your tropical holiday. Thailand, South
America and Africa are exciting destinations, but they are also places where malaria is endemic. In
1998, 1,110 people in England and Wales came down with the disease after holidays in tropical
countries.
An increase in international trade and travel, resistance to traditional anti-malaria drugs and a shortage
of new ideas for tackling the problem have meant that malaria is actually a bigger public health
problem than AIDS.
Global warming could make the situation worse, as the mosquitoes which carry the disease would
come to thrive in more areas.
Malaria occurs in more than 100 tropical and sub-tropical countries, threatening the health and
livelihood of around 40% of the world’s population.
There are an estimated 300 to 500 million cases a year and around 2 million deaths, mainly among the
young. Malaria is caused by a protozoan(single-celled) parasite of the Plasmodium species, carried to
its human host by Anopheles mosquitoes. These also carry other diseases, such as dengue fever.
Four Plasmodium species are known to cause malaria, of which P.falciparum is responsible for the
most cases, the severest symptoms and up to 95% of deaths.
Complex Interaction
A mosquito is simply a small two-winged fly, weighing around 2 milligrams. It travels at
approximately 2.5 km/h and its range can extend up to 160 km. Where it differs from the
comparatively innocent housefly is in the way it acts as a vector, transferring parasites to a human
host.
The interaction between mosquito, parasite and human is complex, although unravelling the details
has given researchers new ideas for how to prevent malaria by interrupting the process.
The female mosquito sees a human as a source of protein to produce its eggs. She has mouthparts
adapted to suck human blood, and she even introduces an anti-coagulant which stops the blood from
clotting so the transfer to the mosquito is unimpeded.
Meanwhile, parasite spores are transferred from the mosquito’s saliva to the bloodstream in a form
known as sporozoites. The sporozoites then travel to the liver, where they multiply and form another
kind of spore, called merozoites.
These enter the bloodstream and penetrate red cells, where they devour haemoglobin. The blood cell
then disintegrates, and the merozoites infect other host cells.
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While this happens, the host develops symptoms that include fever, shivering, headache, joint pains,
vomiting, convulsions and possibly coma. Severe anaemia and infection of the brain may be fatal. It is
thought that the sudden chills so characteristic of the disease happen when the merozoites burst out of
the red blood cells.
Remedies
There are several ways of tackling the malaria problem. The first, and most obvious, is to kill off the
mosquito carriers. Traditionally, this has been done by spraying DDT, although over the years we have
come to realise that this pesticide is toxic to wildlife and the environment. The global ban on DDT by
227 is viewed with concern by experts, because poor countries cannot afford other control measures,
as the more advanced nations have failed to put resources into developing alternatives.
However, other pesticides do seem to give good results against malaria. Pyrethrum, a naturally
occurring insecticide derived from chrysanthemums, can cut child mortality if applied consistently to
bednets and curtains. Biological control is another possible way of supplementing, or even replacing,
chemical insecticides. For instance, Microsporidia, another protozoan parasite from Thailand,
produces spores in the female mosquito which infect her eggs, killing them before they can mature.
This breaks the reproductive cycle and so weakens the mosquito population. Tests of this type are
already under way in Florida and Argentina. Various genetic engineering projects are under way too,
in which the genes from natural insecticides are transferred to bacteria that can infect mosquitoes.
Moreover, better mosquito repellents are being developed, but unfortunately it is not clear yet why
some people get a lot of bites and others none. The answer must lie in the different chemicals
produced by the skin, and the skin really produces hundreds of chemicals. Plenty of mosquito
repellents already exist but there is a need for more effective ones.
Another line of resistance against malaria is drugs, which are used to prevent and to treat the disease.
The first successful anti-malaria drug was quinine, derived from the bark of the Peruvian chichona tree
in the 17th century. Quinine is still used, along with several other drugs, such as chloroquine,
proguanil, mefloquine. They work clearing the malaria parasites from the bloodstream. The problem is
that P.falciparum has evolved resistance to some of these drugs in many areas of the world.
The emergence of resistance underlines the need for better drugs. However, since those who need new
drugs cannot afford the higher cost, the pharmaceutical industry has invested little in this area. Just one
new anti-malaria drug, artemether, has emerged in the past few years.
A particular problem has also arisen with the use of some anti-malaria drugs: serious neuropsychiatric
side effects such as anxiety, depression, nightmares, hallucinations, and even psychosis.
Vaccines
Vaccines may offer the best way to tackle malaria, and several more vaccines are under development.
Meanwhile, researchers are trying to crack the genome of the parasite, which is likely to provide new
ideas for both drug and vaccine development.
Exercise. Answer the following questions.
1. Where is malaria found in the world today?
2. What is the cause of malaria?
3. What are the symptoms of the disease? Can it be fatal?
4. How is the disease treated? Can it be prevented?
5. How can the problem of malaria be resolved?
6. Why isn’t there more research in anti-malaria drugs?
Text 9.
Diseases: What to Do
GLUE EAR (CHRONIC 0TITIS MEDIA)
Symptoms: a feeling of "fullness" in the ear; the patient appears to be slightly deaf in one or both ears.
Glue ear is the non-medical term for a build-up of fluid in the middle ear due to swelling and blockage
in the Eustachian tube. Chronic otitis media, as it is also known, is painless but should be taken
seriously as it may cause deafness.
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What to do: if you suspect that you or your child cannot hear properly, consult your doctor. If it is
mild, he will probably prescribe antibiotics and medication to reduce the swelling. In more severe
cases he will refer you to an ENT specialist.
ECZEMA
Symptoms: patches of red, dry, itchy skin on the face, hands, creases of the limbs. Itchiness may affect
sleep. Eczema tends to run in families. It can be triggered by certain food, pet fur, washing powders,
and also stress. Most children grow out of eczema but may develop other related allergic conditions
such as asthma or hay fever later.
What to do: consult your doctor if you suspect eczema, particularly if there is a family history of
eczema, asthma or hay fever. He may prescribe moisturising creams to reduce the symptoms and in
severe cases a weak steroid cream maybe advised. He will also suggest emollient creams for the bath,
which help to keep the skin smooth and moisturised. Food exclusion diets are generally needed only if
you have severe eczema or a history of intolerance in which case it is important to see a dietician.
LARYNGITIS
Symptoms: hoarseness or loss of voice, pain and discomfort in the throat, dry cough, temperature.
Inflammation of the larynx (voice box) is usually caused by a viral infection. although an allergy may
also be to blame.
What to do: take paracetamol for the temperature and plenty of fluids.. A damp atmosphere will help:
place a bowl of water over a warm radiator in your room. If the hoarseness lasts more than a few days,
consult your doctor.
JAUNDICE
Symptoms: yellowing of the skin and whites of the eyes. Older children may also have flu-like
symptoms, a headache, nausea and vomiting. Jaundice often affects babies soon after birth,
particularly if born prematurely, because of liver immaturity. In older children jaundice is rare, but can
be caused by hepatitis (inflammation of the liver) which occurs most commonly in response to a viral
infection. Certain types of anaemia and malformation or blockage of the bile duct can also lead to
jaundice.
What to do: consult your doctor. Neonatal jaundice usually clears within a few days without treatment
although phototherapy (treatment with light which helps to breakdown pigments which have
accumulated in the blood due to liver immaturity) may be needed. Very rarely, jaundice may be a sign
of liver disease.
For older children and adults with any of these symptoms, consult your doctor immediately.
Admission to hospital may be necessary.
(from an article by Jane Collins, in The Times, March 6, 2001)
Exercise. Say if the following sentences are true (t) or false(f) and then correct the false ones making
them true.
1. _____ With chronic otitis, a person can feel completely deaf in one or both ears.
2. _____ A person with chronic otitis could become deaf even if he doesn’t feel any pain.
3. _____ Eczema causes itchiness.
4. _____ Eczema is often hereditary.
5. _____ Strong steroid creams are often prescribed for eczema sufferers.
6. _____ Laryngitis may cause cough and a fever.
7. _____ A damp room can make laryngitis worse.
8. _____ Jaundice very rarely affects babies right after birth.
Text 10.
Skin So Fixed
A topical lotion with DNA-repair enzymes cuts down skin carcinomas
Every year about 1.3 Americans are diagnosed with basal or squamous cell carcinoma, the two most
common forms of skin cancer. The sun’s ultraviolet light is the chief culprit in causing genetic
25
mutations in skin cells. Researchers now say they have a skin lotion that can enter cells and fix their
damaged DNA before they have a chance to develop into fullblown cancer cells.
The principle is simple: the lotion contains liposomes, little oily vesicles, filled with a viral DNArepair enzyme called “T4 endonuclease V”. the liposomes penetrate the epidermis and enter the cells.
Once released inside, the enzymes are small enough to make their way into the nucleus, which
contains the DNA. Here they bind very tightly to the most common DNA mutations caused by
sunlight – so called “cyclobutane pyrimidine dimers”, in which two DNA bases are fused. By partially
cutting off the dimmers and breaking the DNA strand next to them, the enzymes initiate a repair
process that other cellular enzymes complete. The viral endonuclease is not the only repair protein
that has been tested in a lotion. For example a dermatologist at the University of Dusseldorf published
a study last year using a fascinating DNA-repair enzyme from cyanobacteria. It directly reverts UVinduced dimers back to normal, using the energy of visible light. Applied in liposomes, the enzyme
decreased the number of dimers in human skin by about 40%.
Protein therapy is nothing new – insulin and human growth hormone have been used for years – but
applying proteins externally to the skin is. Delivering biologically active protein through skin might
also become a way to treat other inherited skin diseases caused by enzyme deficiencies.
Exercise. Answer the following questions.
1. What does sunlight provoke?
2. What are the most common forms of skin cancer?
3. What is the latest therapy now in use and how is it different from those in the past?
4. What are some other protein therapies already in use today?
Text 11.
The Market for Human Tissue in the Biotechnology Age
It seems that scientists have been struggling forever to make a mechanical heart that really works, or a
trouble-free hearing aid. Or a prosthetic hand that's half-as good as the real thing. From wooden legs to
silicone breasts, the history of human corporeal re-engineering has largely been one of clumsiness and
frustration, despite relentless innovation.
But what if we could take a tip from nature and grow the things we cannot build ? Imagine little slabs
of cardiac muscle cultivated in a dish, ready to be sewn over your aging heart.
Homegrown blood vessels that naturally bypass clogged arteries. Medicines that work perfectly
because they are made by your own cells.
The dream of harnessing biology's regenerative powers for curative, life-extending and even cosmetic
purposes has begun to become a reality, write Lori Andrews and Dorothy Nelkin in Body Bazaar: The
Market for Human Tissue in the Biotechnology Age. But, the authors warn, this new and promising
era has a dark side. People's tissues, cells and genes are increasingly being perceived as natural
resources to be harvested and transformed into value- added commodities. And the economy that has
evolved around this burgeoning industry threatens to wreak ethical havoc. Consider the case of John
Moore, who in the 1980s was being treated by a Los Angeles specialist for hairy-cell leukemia.
Unbeknownst to Moore, his doctor had discovered in the businessman's spleen cells a natural
compound that appeared to have great therapeutic potential. When Moore learned that his doctor had
taken out a patent on his cells and had sold the commercial rights to a biotechnology company for
millions of dollars, he sued for property theft. But the California Supreme Court decided that Moore
did not have a property interest in his body parts. Thus, the stage was set for what the biotechnology
industry now sees as a crucial right of access to human tissues and what critics like Andrews and
Nelkin see as an invitation to wholesale bio-colonialism and human exploitation.
Oral Exercise. Give some reasons for and against using biotechnology to improve our lives.
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