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Science MagazineScience MagazineScience MagazineScience Magazine

Interesting

experiments and

Chemistry Jokes

available!

What are yellow

explosive—the

TNTs?

The HOT topic—

Nuclear Crisis in

Japan

Learn more

about Hormones

Cooperated with Biology Society

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Preface

Thank you for supporting the Science Magazine published

in the 1st term of the academic year. Knowing that students

are pursuing knowledge of Science, we - members of the

Science Society and Biology Society work hard to publish

the 2nd Science Magazine in the second half of the

academic year.

In an attempt to provide you with more amazing science

information, the Science Society and the Biology Society

worked on the 2nd term magazine together. To provide

all-round science knowledge to you, we give details about

light, nuclear crisis in Japan, the yellow explosive in

Chemistry and the hormone in biology. Last but not least,

we have prepared an interesting topic which you are going

to love it. You are sure to have a lot of fun in the world of

chemistry. Do not hesitate! Let’s enjoy the Science

Magazine and discover the world around us!

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Content

Physics

1. How fast can light travel? P.4-5

Chemistry

1. The Japan Earthquake and Nuclear Crisis P.6-10

2. Having fun in Chemistry P.11-13

3. Yellow explosive- TNT P.14-17

Biology

1. Hormones in Organisms P.18-34

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HOW FAST CAN LIGHT TRAVEL?HOW FAST CAN LIGHT TRAVEL?HOW FAST CAN LIGHT TRAVEL?HOW FAST CAN LIGHT TRAVEL?

We sometimes describe fast-moving objects moving as fast as light,

but actually how fast is light? 10,000 ms�� ? 1,000,000 ms-1?

10,000,000 ms-1? Or actually infinity? This question has puzzled

numerous scientists for centuries. In the 19th century Hippolyte

Fizeau developed a method to determine the speed of light based on

time-of-flight measurements on Earth and reported a value of

315,000 kms-1. His method was improved upon by Léon Foucault who

obtained a value of 298,000 kms-1 in 1862. How could they measure

the speed of light? Let’s discover!

Diagram of the Foucault apparatus

A method of measuring the speed of light is to measure the time

needed for light to travel to a mirror at a known distance and back.

This is the working principle behind the Foucault apparatus

developed by Hippolyte Fizeau and Léon Foucault.

The setup as used by Fizeau consists of a beam of light directed at a

mirror 8 kilometres (5 miles) away. On the way from the source to the

mirror, the beam passes through a rotating cogwheel. At a certain rate

of rotation, the beam passes through one gap on the way out and

another on the way back, but at slightly higher or lower rates, the

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beam strikes a tooth and does not pass through the wheel. Knowing

the distance between the wheel and the mirror, the number of teeth

on the wheel, and the rate of rotation, the speed of light can be

calculated.

The method of Foucault replaces the cogwheel

by a rotating mirror. Because the mirror keeps rotating while the light

travels to the distant mirror and back, the light is reflected from the

rotating mirror at a different angle on its way out than it is on its way

back. From this difference in angle, the known speed of rotation and

the distance to the distant mirror the speed of light may be

calculated.

Nowadays, using oscilloscope with time resolutions of less than one

nanosecond, the speed of light can be directly measured by timing the

delay of a light pulse from a laser or an LED reflected from a mirror.

This method is less precise (with errors of the order of 1%) than

other modern techniques, but it is sometimes used as a laboratory

experiment in college physics classes.

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The Japan Earthquake and Nuclear Crisis

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History of Nuclear Power in Japan

In 1954, Japan budgeted 230

million yen for nuclear energy,

marking the beginning of the

program. The first nuclear

reactor in Japan was built by

the UK's General Electric

Company. In the 1970s the

first Light Water Reactors

were built in co-operation

with American companies.

These plants were bought

from U.S. vendors such as General Electric or Westinghouse with

contractual work done by Japanese companies, who would later get a

license themselves to build similar plant designs. Developments in

nuclear power since that time has seen contributions from Japanese

companies and research institutes on the same level as the other big

users of nuclear power.

Since 1973, nuclear

energy has been a

national strategic

priority in Japan, as

the nation is heavily

dependent on

imported fuel, with

fuel imports

accounting for 61%

of energy production.

In 2008, after the

opening of 7 brand new nuclear reactors in Japan (3 on Honshu, and

1 each on Hokkaido, Kyushu, Shikoku, and Tanegashima) Japan

became the third largest nuclear power user in the world with 55

nuclear reactors. These provide 34.5% of Japan's electricity.

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How to Prevent Nuclear Crisis in Japan

Following an earthquake, tsunami,

and the failure of cooling systems at

the Fukushima I Nuclear Power Plant

on March 11, 2011, a nuclear

emergency was declared. This was the

first time a nuclear emergency had

been declared in Japan, and 140,000

residents within 20 km of the plant

were evacuated. The amount of

radiation released is unclear, and the

crisis is still ongoing.

With the loss of power at reactors, and with its valves and pumps

damaged by the tsunami, the fuel rods in the reactors are still under

high temperature. Because of the high temperature, the radiation is

given out from the fuel rods. In order to avoid the spreading of

radiation, the emergency workers were pumping in seawater to cool

down the fuel rods. At the same time, they mixed the water with an

element Boron.

Boron is the chemical element with atomic number 5 and the

chemical symbol B. Because of its high neutron cross-section,

boron-10 is often used to control fission in nuclear reactors as a

neutron-capturing substance. In this crisis, Boron is used to disrupt

the nuclear chain reactions in the reactors, and then the fuel rods can

be cooled down.

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Can Apply Iodine Solution onto the body surface

prevent or treat radiation-related injuries?

When there is an

accident involving

damage to the nuclear

reactor causing

leakage, radioactive

materials in the

reactor core may be

released into the

atmosphere. The

radioactive caesium

(Cs-137) and

radioactive iodine

(I-131) are the most

abundant radionuclides that may be released into the atmosphere

during the accident. Recently, many people buy iodine solution to

prevent the radiation-related injury.

131I decays with a half-life of 8.02 days with beta and gamma

emissions. This nuclide of iodine atom has 78 neutrons in nucleus;

the stable nuclide 127I has 74 neutrons. On decaying, 131I transforms

into 131Xe:

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Iodine in food is absorbed by the body and preferentially

concentrated in the thyroid where it is needed for the functioning of

that gland. When 131I is present in high levels in the environment

from radioactive fallout, it can be absorbed through contaminated

food, and will also accumulate in the thyroid. As it decays, it may

cause damage to the thyroid. The primary risk from exposure to high

levels of 131I is the chance occurrence of radiogenic thyroid cancer in

later life.

There is no scientific evidence that eating salt or applying iodine

onto the body surface can prevent or treat radiation-related injury.

Applying iodine solution onto body surface may cause skin irritation.

More information on Japan nuclear crisis:

http://www.bbc.co.uk/news/world-asia-pacific-13017282

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

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Having Fun in Chemistry

It seems that it’s a bit boring when we study chemistry. However,

beyond the textbook, Chemistry is full of fun and interesting! Let’s get

into the Fun Chemistry World!

MAGIC: Get Away PEPPER!!

It may be the easiest magic in the world. You can find all the ‘magic’

tools you need at home.

• black pepper

• water

• detergent (dishwashing liquid)

• plate or bowl

Steps:

1. Fill the plate or bowl with water until it is

FULL.

2. Spread some pepper on the water.

3. Dip your finger into the centre of the water, there will be not

much effects.

4. Put a drop of detergent on your finger and dip it into the centre

of the water. The pepper will move away from your finger!

Notes:

If you are doing this trick, you may first

prepare a clean finger (for step 3) and a

finger with detergent (for step 4). It makes

your trick more realistic!

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Principle behind the GREAT trick:

Normally, there is a surface tension

on the water surface and the tension

makes the water bugles up a bit. The

tension ‘holds’ the water in the plate.

When you add detergent into the

water, the tension becomes lower

than usual and hence the water wants

to spread out. As the water flattens on

the plate, the pepper then floats up

and moves (carried by water) to the

edge of the plate as if by magic.

Hey magicians! Show this magic to your friends in lunchtime!

Chemistry Jokes

Don’t think chemists are just boring guys! They have a great sense of

humor!

Do you have a chemistry joke or riddle or are you looking for one?

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Helium

Helium walks into a bar and orders a beer, the bartender says, "Sorry,

we don't serve noble gases here." He doesn't react.

Chemical formula of water

Teacher: What is the chemical formula of water?

Pupil: HIJKLMNO (H2O , ‘H to O’)

What solution is it?

How do you call a tooth suspended in a litre of water?

Answer:a 1 molar solution

Neutron

A neutron walks into a shop,

"I’d like a 'coke', he says.

The shop keeper serves up the coke.

"How much will that be?" Asked the neutron.

"For you?" Replied the shop keeper, "No charge!"

Why chemists are great

Why are chemists so great at solving problems?

Answer: Because they have all the solutions.

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The Yellow Explosive – TNT Trinitrotoluene (abbreviated as TNT), or more specifically, 2, 4, 6 -

trinitrotoluene, is a chemical compound with the formula C6H2

(NO2)3CH3. This yellow-coloured solid is sometimes used as a reagent

in chemical synthesis, but it is best known as a useful explosive

material with convenient handling properties. The explosive yield of

TNT is considered to be the standard measure of strength of bombs

and other explosives.

TNT was first prepared in 1863 by German

chemist Julius Wilbrand and originally used as

a yellow dye. Its potential as an explosive was

not appreciated for several years mainly

because it was so difficult to detonate and

because it was less powerful than alternatives.

TNT can be safely poured when liquid into

shell cases, and is so insensitive that in 1910, it

was exempted from the UK's Explosives Act

1875 and was not considered an explosive for

the purposes of manufacture and storage. The

German armed forces adopted it as a filling for

artillery shells in 1902. TNT-filled

armor-piercing shells would explode after they

had penetrated the armor of British capital

ships, whereas the British lyddite-filled shells

tended to explode upon striking armor, thus

expending much of their energy outside the

ship. The British started replacing lyddite with

TNT in 1907. TNT is still widely used by the United States military

and construction companies around the world. The majority of TNT

currently used by the US military is manufactured by Radford Army

Ammunition Plant near Radford, Virginia.

It is a common misconception that TNT and dynamite are the same,

or that dynamite contains TNT. In fact, whereas TNT is a specific

chemical compound, dynamite is an absorbent mixture soaked in

nitroglycerin (硝化甘油) that is compressed into a cylindrical shape

and wrapped in paper.

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Upon detonation, TNT decomposes as a mix of follows:

2 C7H5N3O6 → 3 N2 + 5 H2O + 7 CO + 7 C

2 C7H5N3O6 → 3 N2 + 5 H2 + 12 CO + 2 C

The reaction is exothermic but has high activation energy. Because of

the production of carbon, TNT explosions have a sooty appearance.

Because TNT has an excess of carbon, explosive mixtures with

oxygen-rich compounds can yield more energy per kilogram than

TNT alone. During the 20th century, amatol, a mixture of TNT with

ammonium nitrate was a widely used military explosive.

Detonation of TNT can be done using a high velocity initiator or by

efficient concussion.

For many years, TNT used to be the reference point for the Figure of

Insensitivity. TNT has a rating of exactly 100 on the F of I scale.

However, the reference has since been changed to a more sensitive

explosive called RDX (旋風炸藥/黑索金 or Hexogen) , which has an F

of I of 80.

TNT contains 4.7 megajoules per kilogram. The energy density of

TNT is used as a reference-point for many other types of explosives,

including nuclear weapons, the energy content of which is measured

in kilotons (~4.184 terajoules) or megatons (~4.184 petajoules) of

TNT equivalent.

For comparison, gunpowder contains 3 megajoules per kilogram,

dynamite contains 7.5 megajoules per kilogram, gasoline contains

47.2 megajoules per kilogram (though gasoline requires an oxidant,

so an optimized gasoline and O2 mixture contains 10.4 megajoules

per kilogram), and butter contains 30 megajoules per kilogram (but

not an explosive).

TNT is one of the most commonly used explosives for military and

industrial applications. It is valued because of its insensitivity to

shock and friction, which reduces the risk of accidental detonation.

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TNT melts at 80 °C (176 °F), far below the temperature at which it

will spontaneously detonate, allowing it to be poured as well as safely

combined with other explosives. TNT neither absorbs nor dissolves

in water, which allows it to be used effectively in wet environments.

Additionally, it is stable compared to other high explosives.

TNT is poisonous, and skin contact can cause skin irritation, causing

the skin to turn into a bright yellow-orange colour. During the First

World War, munitions workers who handled the chemical found that

their skin turned bright yellow, which resulted in their acquiring the

nickname "canary girls" or simply "canaries."

People exposed to TNT over a prolonged period tend to experience

anemia and abnormal liver functions. Blood and liver effects, spleen

enlargement and other harmful effects on the immune system have

also been found in animals that ingested or breathed trinitrotoluene.

There is evidence that TNT adversely affects male fertility, and TNT is

listed as a possible human carcinogen. Consumption of TNT produces

red urine through the presence of breakdown products and not blood

as sometimes believed.

Some military testing grounds are contaminated with TNT.

Wastewater from munitions programs including contamination of

surface and subsurface waters may be coloured pink because of the

presence of TNT. Such contamination, called "pink water", may be

difficult and expensive to remedy.

TNT is prone to exudation of dinitrotoluenes (DNT) and other

isomers of trinitrotoluene. Even small quantities of such impurities

can cause such effect. The effect shows especially in projectiles

containing TNT and stored at higher temperatures, e.g. during

summer. Exudation of impurities leads to formation of pores and

cracks (which in turn cause increased shock sensitivity). Migration of

the exudates liquid into the fuse screw thread can form fire channels,

increasing the risk of accidental detonations; fuse malfunction can

result from the liquids migrating into its mechanism.

Industrially, TNT is synthesized in a three-step process. First,

toluene is nitrated with a mixture of sulfuric and nitric acid to

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produce mono-nitrotoluene or MNT. The MNT is separated and then

renitrated to dinitrotoluene or DNT. In the final step, the DNT is

nitrated to trinitrotoluene or TNT using an anhydrous mixture of

nitric acid and oleum. Nitric acid is consumed by the manufacturing

process, but the diluted sulphuric acid can be reconcentrated and

reused. Subsequent to nitration, TNT is stabilized by a process called

sulphitation, where the crude TNT is treated with aqueous sodium

sulfite solution in order to remove less stable isomers of TNT and

other undesired reaction products. The rinse water from sulphitation

is known as red water and is a significant pollutant and waste

product of TNT manufacture.

Control of nitrogen oxides in feed nitric acid is very important

because free nitrogen dioxide can result in oxidation of the methyl

group of toluene. This reaction is highly exothermic and carries with

it the risk of runaway reaction and explosion.

In the laboratory, 2, 4, 6-trinitrotoluene is produced by a two step

process. A nitrating mixture of concentrated nitric and sulphuric

acids is used to nitrate toluene to a mixture of mono- and

di-nitrotoluene isomers, with cooling to maintain careful temperature

control. The nitrated toluenes are separated, washed with dilute

sodium bicarbonate to remove oxides of nitrogen, and then carefully

nitrated with a mixture of fuming nitric acid and sulphuric acid.

Towards the end of the nitration, the mixture is heated on a steam

bath. The trinitrotoluene is separated, washed with a dilute solution

of sodium sulphite and then recrystallized from alcohol.

Detonation of the 500-ton TNT explosive

charge as part of Operation Sailor Hat in

1965. The white blast-wave is visible on the

water surface and a shock condensation

cloud is visible overhead

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Hormones Do you know why eating chocolate can make you less stressful and happier? Do you

know why a plant can grow towards sunlight? Do you know why you would tremble

and your heart beats faster when you are keyed up? If you don’t, you should take a

look at these articles concerning hormones. Living organisms’ daily lives are closely

related to hormones. A small act made by a person, the coordination of your body,

your emotion or even your health are also coordinated or controlled by hormones. Not

only in animals, are hormones also present in plants and fruits. Different types of

hormones have different functions. As we could see, hormones are greatly related to

our daily lives!

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A hormone is a chemical released by a cell or a gland in one part of the body that sends

out messages affecting cells in other parts of the organism. Only a small amount of

hormone is required to alter cell metabolism. In essence, it is a chemical messenger that

transports a signal from one cell to another. All multicellular organisms produce

hormones; plant hormones are also called phytohormones. Hormones in animals are

often transported in the blood.

-Hormones transported in blood

Cells respond to a hormone when they express a specific receptor for that hormone. The

hormone binds to the receptor protein,

resulting in the activation of a signal transduction mechanism that ultimately leads to

cell type-specific responses.

Endocrine hormone molecules are secreted directly into the bloodstream, whereas

exocrine hormones are secreted directly into a duct, and, from the duct, they flow either

into the bloodstream or from cell to cell by diffusion in a process known as paracrine

signalling.

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-Exocrine hormones are secreted directly into a duct

Recently it has been found that a variety of exogenous modern chemical compounds

have hormone-like effects on both humans and wildlife. Their interference with the

synthesis, secretion, transport, binding, action, or elimination of natural hormones in

the body are responsible of homeostasis, reproduction, development, and behavior

changes in the same way as the endogenous produced hormones.

Hormone cells are typically of a specialized cell type, residing within a particular

endocrine gland, such as thyroid gland, ovaries, and testes. Hormones exit their cell of

origin via exocytosis or another means of membrane transport. Cellular recipients of a

particular hormonal signal may be one of several cell types that reside within a number

of different tissues, as is the case for insulin, which triggers a diverse range of systemic

physiological effects. Different tissue types may also respond differently to the same

hormonal signal. Because of this, hormonal signalling is elaborate and hard to dissect.

-Exocytosis and endocytosis

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Physiology of hormones

In physiology, the endocrine system is a system of glands, each of which secretes a

type of hormone directly into the bloodstream to regulate the body. The endocrine

system is in contrast to exocrine system, which secretes its chemicals using ducts. It

derives from the Greek words endo (Greek ένδο) meaning inside, within, and crinis

(Greek κρινής) for secrete. The endocrine system is an information signal system like

the nervous system, yet its effects and mechanism are classifiably different. The

endocrine systems effects are slow to initiate and prolonged in their response, lasting

for hours to weeks. Hormones are substances (chemical mediators) released from

endocrine tissue into the bloodstream where they travel to target tissue and generate a

response. Hormones regulate various human functions, including metabolism, growth

and development, tissue function, and mood. The field of study dealing with the

endocrine system and its disorders is endocrinology, a branch of internal medicine.

Most cells are capable of producing one or more molecules, which act as signalling

molecules to other cells, altering their growth, function, or metabolism. The classical

hormones produced by cells in the endocrine glands are cellular products, specialized to

serve as regulators at the overall organism level. However, they may also exert their

effects solely within the tissue in which they are produced and originally released.

Hormone secretion can be stimulated and inhibited by other hormones, plasma

concentrations of ions or nutrients, binding globulins, neurons and mental activity, and

environmental changes.

-Negative feedback mechanism

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The rate of hormone biosynthesis and secretion is often regulated by a homeostatic

negative feedback control mechanism. Such a mechanism depends on factors that

influence the metabolism and excretion of hormones. Thus, higher hormone

concentration alone cannot trigger the negative feedback mechanism. Negative

feedback must be triggered by overproduction of an "effect" of the hormone.

To release active hormones quickly into the circulation, hormone biosynthetic cells

may produce and store biologically inactive hormones in the form of pre- or

prohormones. These can then be quickly converted into their active hormone form in

response to a particular stimulus.

Functions of hormones

1. Stimulation or inhibition of growth.

2. Mood swings.

3. Induction or suppression of apoptosis (programmed cell death).

4. Activation or inhibition of the immune system.

5. Regulation of metabolism.

6. Preparation of the body for mating, fighting, fleeing, and other activities.

7. Preparation of the body for a new phase of life: puberty, parenting, and menopause.

8. Control of the reproductive cycle.

9. Hunger cravings.

10. Regulate the production and release of other hormones.

11. Control the internal environment of the body through homeostasis.

Endocrine organs and secreted hormones

-Endocrine glands in the human head, neck and the hormones secreted

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-Endocrine glands of alimentary system and the hormones secreted

-Endocrine glands of reproductive system and the hormones secreted

-Hormones for calcium regulation -Hormones for other metabolic activities

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Chemical classes of hormones

Vertebrate hormones fall into three chemical classes:

Peptide hormones consist of chains of amino acids. Examples of small peptide

hormones are TRH and vasopressin.

-Thyrotropin-releasing hormone’s chemical structure

Peptides composed of scores or hundreds of amino acids are referred to as proteins.

Examples of protein hormones include insulin and growth hormone.

-Insulin model

More complex protein hormones bear carbohydrate side-chains and are called

glycoprotein hormones. Luteinizing hormone, follicle-stimulating hormone and

thyroid-stimulating hormone are glycoprotein hormones. There's also another type of

hydrophilic hormones. They are called non-peptide hormones. Although they don't

have peptide connections, they are assimilated as peptide hormones.

Lipid and phospholipid-derived hormones derive from lipids such as linoleic acid,

arachidonic acid and phospholipids. The main classes are the steroid hormones that

derive from cholesterol and the eicosanoids. Examples of steroid hormones are

testosterone and cortisol.

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-Testosterone’s chemical structure

Sterol hormones such as calcitriol are a homologous system. The adrenal cortex and

the gonads are primary sources of steroid hormones. Examples of eicosanoids are the

widely studied prostaglandins.

-Monoamine’s chemical structure

Monoamines derived from aromatic amino acids like phenylalanine, tyrosine,

tryptophan by the action of aromatic amino acid decarboxylase enzymes. Examples of

monoamines are thyroxine and adrenaline.

Diseases of abnormal hormonal functioning

Diseases of the endocrine system are common, including conditions such as diabetes

mellitus, thyroid disease, and obesity. Endocrine disease is characterized by

deregulated hormone release (a productive pituitary adenoma), inappropriate response

to signalling (hypothyroidism), lack of a gland (diabetes mellitus type 1, diminished

erythropoiesis in chronic renal failure), or structural enlargement in a critical site such

as the thyroid (toxic multinodular goitre). Hypo-function of endocrine glands can occur

as a result of loss of reserve, hypo-secretion, agenesis, atrophy, or active destruction.

Hyper-function can occur as a result of hyper-secretion, loss of suppression,

hyperplastic or neoplastic change, or hyper-stimulation.

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-Hyperthyroidism

As the thyroid, and hormones have been implicated in signalling distant tissues to

proliferate, for example, the estrogen receptor has been shown to be involved in certain

breast cancers. Endocrine, paracrine, and autocrine signalling have all been implicated

in proliferation, one of the required steps of oncogenesis.

-Diabetes -Obesity

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Animal Hormones

Androgen

Androgen, also called testoid, is usually a steroid hormone presented in males’ testes

of animals. It controls and stimulates the development as well as the maintenance of

male characteristic in vertebrates by binding to the androgen receptors. The activity of

male sex organs and the development of male secondary sex characteristics (body hair,

deep voice) are also included in androgen’s functions. The most well-known androgen

is testosterone, which can be found in mammals, birds, reptiles and other vertebrates.

Human androgens have a wide range of functions from birth to death. These steroids

are essential to life and function as we have come to understand it. They are also

abused extensively because of their virilizing effect and other body image enhancing

properties. They have been banned in competitive sports but continue to be used

widely.

Androgens inhibit fat deposition. Most of us are aware that males have less fat tissue

than females. This is due to the fact that androgens inhibit the ability of fat cells to

store lipids. This occurs because androgens block the transduction pathway which

normally supports adipocyte function in mammals.

Androgens increase muscle mass. Generally males have greater

amounts of muscle tissues than females due to higher amount of

androgens present. Androgens are known to promote the

enlargement of skeletal muscle cells by acting in a coordinated

manner to enhance muscle functions by acting on many

different types of cells.

Athletes who abuse androgens gain muscle mass over a short

period of time. One must be alert to mood changes in such

clients as hormone levels rise and fall in unpredictable patterns.

Androgens act on the brain too. Circulating androgens affect human behaviour.

Higher levels of androgens are associated with more aggression, energy levels and

drive to achieve goals. This happens because androgens influence human neurons by

making them more sensitive to steroid hormones. Many studies show that androgen

levels are directly proportional to human aggression.

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Insensitivity to androgens is fairly rare but does occur. Androgen resistance

syndrome is a disorder due to a mutation of gene encoding. It is called androgen

resistance. This results in under verilization or infertility in XY persons of either sex.

Insensitivity to androgens can also result in several types of intersex conditions.

Oxytocin

Oxytocin is a hormone that humans naturally create in the body, that also functions as

a neurotransmitter in the hypothalamus located deep in the brain, which regulates

specific physiological functions like body temperature, hunger, thirst, as well as fight

or flight emotions like fear and trust.

It is released naturally particularly in females who are in labour during child birth,

and it plays an important part in breastfeeding. It is also released in both males and

females during sexual activity and orgasm. The hormone is also released naturally

during hugging and pleasant physical touching between individuals, and the bonding

of a mother and her new born baby.

Oxytocin is best known for roles in female reproduction: 1) it is released in large

amounts after distension of the cervix and uterus during labour, and 2) after

stimulation of the nipples, facilitating birth and breastfeeding. Recent studies have

begun to investigate oxytocin's role in various behaviours, including orgasm, social

recognition, pair bonding, anxiety, and maternal behaviours. Therefore, it is often

referred to as the ‘love hormone’. It is known to directly affect human communication

through the eyes, which is an integral part of emotional interaction between

individuals.

29

Oxytocin is responsible for the increase in levels of

trust between people, which increases social

bonding and may be a viable antidote for depression,

social phobias and shyness. It also plays a part in the

social recognition of facial expressions, some think by

altering the firing of the amygdala, which is the part of

the brain that is primarily responsible for stimulating

emotion.

Oxytocin also stimulates contractions of the smooth muscle tissue in the wall of the

uterus during childbirth. Prior to the late stages of pregnancy, the uterus is relatively

insensitive to oxytocin. As the time of delivery approaches, the muscles become

sensitive to increased secretion of oxytocin. After delivery, oxytocin stimulates the

ejection of milk from the mammary glands. The suckling of an infant stimulates the

nerve cells in the brain to release oxytocin. Once oxytocin is secreted into the

circulatory system, special cells contract and release milk into collecting chambers

from which the milk is released. This reflex is known as the milk let-down reflex.

Thyroxine

The thyroid hormones are tyrosine-based hormones produced by the thyroid

gland primarily responsible for regulation of metabolism. An important component in

the synthesis of thyroid hormones is iodine.

Most of the thyroid hormone circulating in the blood is bound to transport proteins.

Only a very small fraction of the circulating hormone is free (unbound) and

biologically active, hence measuring concentrations of free thyroid hormones is of

great diagnostic value.

Thyroid hormones are lipophilic substances that are able to traverse cell

membranes even in a passive manner. However, at least 10 different active, energy

30

dependent and genetic

regulated iodothyronine

transporters have been identified in

humans. They guarantee that

intracellular levels of thyroid

hormones are higher than in blood

plasma or interstitial fluids.

The thyronines act on nearly every

cell in the body. They act to increase

the basal metabolic rate,

affect protein synthesis, help

regulate long bone growth (synergy

with growth hormone), neuronal

maturation and increase the body's

sensitivity to catecholamines. The

thyroid hormones are essential to

proper development and

differentiation of all cells of the

human body. These hormones also

regulate protein, fat,

and carbohydrate metabolism,

affecting how human cells use

energetic compounds. They also

stimulate vitamin metabolism.

Numerous physiological and

pathological stimuli influence

thyroid hormone synthesis.

Thyroid hormone leads to heat

generation in humans. However,

the thyronamines function via some unknown mechanism to inhibit neuronal activity;

this plays an important role in the hibernation cycles of mammals and

the molting behaviour of birds. One effect of administering the thyronamines is a

severe drop in body temperature.

31

Plant hormones

Plant hormones are signal molecules produced within the plant, and occur in

extremely low concentrations. Hormones regulate cellular processes in targeted cells

locally and when moved to other locations, in other locations of the plant. Plant

hormones also determine the formation of flowers, stems, leaves, the shedding of

leaves, and the development and ripening of fruit. Plants, unlike animals, lack glands

that produce and secrete hormones, instead each cell is capable of producing

hormones.

Here we will introduce three special plant hormones: ethylene, auxins and cytokinin.

Ethylene

-Ethylene

Ethylene (IUPAC name: ethene) is a gaseous organic compound with the formula

C2H4. It is the simplest alkene (older name: olefin from its oil-forming property).

Because it contains a carbon-carbon double bond, ethylene is classified as an

unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant

hormone.

Ethylene has very limited solubility in water and does not accumulate within the cell

but diffuses out of the cell and escapes out of the plant. Its effectiveness as a plant

hormone is dependent on its rate of production versus its rate of escaping into the

atmosphere. Ethylene is produced at a faster rate in rapidly growing and dividing cells,

especially in darkness.

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-Sunflower seedling, just three days after germination

New growth and newly germinated seedlings produce more ethylene than can escape

the plant, which leads to elevated amounts of ethylene, inhibiting leaf expansion. As the

new shoot is exposed to light, reactions by phytochrome in the plant's cells produce a

signal for ethylene production to decrease, allowing leaf expansion.

Ethylene affects cell growth and cell shape; when a growing shoot hits an obstacle

while underground, ethylene production greatly increases, preventing cell elongation

and causing the stem to swell. The resulting thicker stem can exert more pressure

against the object impeding its path to the surface. If the shoot does not reach the

surface and the ethylene stimulus becomes prolonged, it affects the stems natural

geotropic response, which is to grow upright, allowing it to grow around an object.

Studies seem to indicate that ethylene affects stem diameter and height. When stems of

trees are subjected to wind, causing lateral stress, greater ethylene production occurs,

resulting in thicker tree trunks and branches.

Ethylene also affects fruit-ripening. Normally, when the seeds are mature, ethylene

production increases and builds-up within the fruit, resulting in a climacteric event just

before seed dispersal.

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Auxins

-Auxin

Auxins were the first class of growth regulators discovered. They are compounds that

positively influence cell enlargement, bud formation and root initiation in plant. They

also promote the production of other hormones and in conjunction with cytokinins, they

control the growth of stems, roots, and fruits, and convert stems into flowers. They

affect cell elongation by altering cell wall plasticity. Auxins decrease in light and

increase where it is dark. They stimulate cambium cells to divide and cause secondary

xylem to differentiate in stems. Auxins act to inhibit the growth of buds lower down the

stems (apical dominance), and also to promote lateral and adventitious root

development and growth. Auxins in seeds regulate specific protein synthesis, as they

develop within the flower after pollination, causing the flower to develop a fruit contain

the developing seeds.

-Lack of auxin can cause abnormal growth (right)

Auxins are toxic to plants in large concentrations. Auxins are commonly applied to

stimulate root growth when taking cuttings of plants. The most common auxin found in

plants is indoleacetic acid.

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Cytokinins

-Cytokinins

Cytokinins or CKs are a group of chemicals that influence cell division and shoot

formation. They were called kinins in the past when the first cytokinins were isolated

from yeast cells. They also help delay senescence or the aging of tissues, which are

responsible for mediating auxin transport throughout the plant, and affect intermodal

length and leaf growth. They have a highly synergistic effect in concert with auxins

and the ratios of these two groups of plant hormones affect most major growth periods

during a plant's lifetime. Cytokinins counter the apical dominance induced by auxins;

they are in conjunction with ethylene to promote abscission of leaves, flower parts

and fruits.

Potential Medical Applications of plant hormones

Plant stress hormones activate cellular responses, including cell death, to diverse stress

situations in plants. Researchers have found that some plant stress hormones share the

ability to adversely affect human cancer cells . For example, sodium salicylate has been

found to suppress proliferation of lymphoblastic leukemia, prostate, breast, and

melanoma human cancer cells. Jasmonic acid, a plant stress hormone that belongs to

the jasmonate family, induced death in lymphoblastic leukemia cells. Methyl jasmonate

has been found to induce cell death in a number of cancer cell lines.

-Sodium salicylate -Jasmonic acid

35

References:

http://scienceray.com/biology/human-biology/human-androgens-fu

nctions-uses-and-abuses/2/

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

http://www.answers.com/topic/what-are-the-functions-of-oxytocin

http://buyoxytocin.net/how-oxytocin-works

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

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

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

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

http://legacy.owensboro.kctcs.edu/gcaplan/anat2/notes/APIINotes1

%20how%20endocrine%20works.htm

http://classes.midlandstech.com/carterp/courses/bio210/chap01/c

hap01.html

http://www.bbc.com/

http://chemistry.about.com/od/chemistrymagic/a/peppertrick.htm

http://chemistry.about.com/u/ua/chemistryfunhumor/Chemistry-Jo

kes.htm

36

2010-2011 Committee

Science Society

Teacher advisors: Mr. Lui Kwok Keung

Mr. Yeung Tat Ming

Mr. Kong Kwok Hung

Chairman: 6B Shum Tsz Ho

5D Gast Felix

Vice-chairman: 6B Lam Wai Kit

Secretary: 6B Wu Wing Yan

Treasurer: 6B Chau Yu Chung

Publicist: 5D Yap Ling Fung

Contact: 5D Cheung Yi Ting

Committee: 6A Kwok Chi Kai 5D Chan Tsun Yui

6A Mok Kai Tung 5D Ho Chung Yan

5A Teng Chun Hang 5D Ng Yik Kwong

Biology Society

Teacher advisors: Miss Hui Man Chung

Chairman: 6B Lo Yee

Vice-chairman: 6B Lai Lok Yin

Committee: 6B Fan Sze Nok

6B Wan Tsz Yau

6B Chan Chun Ki

5A Cheung Chung Man

5A Sin Vivian

5A Teng Chun Hang

5D Yeung Tsz Yan

5D Chan Tsz Fung

5D Yap Ling Fung