Volume 17Number 1September 2006

Impact Earth

GCSE Science Review

1 Impact EarthDavid Sang

4 Your futureFood technology

6 Testing new medicinesJane Taylor

8 AlchemyJohn Tucker

11 Improve your gradeEvaluating websites

12 A life in scienceTBL@WWW

14 BiofuelsNigel Collins

17 Blood pressureJane Taylor

20 Places to visitMedical museums in London

22 The human heart

Free book for every subscriber!A single subscription to CATALYST, Volume 17, 2006/2007 is available to individualsat £16.95 per annum. Bulk orders of three or more subscriptions are available at thegreatly reduced rate of £8.95 per subscription, provided all copies can be mailed tothe same addressee for internal distribution. CATALYST is published four timesthrough the school year, in September, November, February and April. Orders can beplaced at any time during the year, and the issues already published will be suppliedautomatically. Only orders for complete volumes can be accepted.Every subscriber will also receive a copy of Philip Allan Updates’ GCSE ScienceEssential Word Dictionary (worth £5.99) FREE with the November issue. This offerapplies only to UK subscribers.Overseas rates are available on request.

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Contents

The front cover shows anasteroid approaching Earth(Detlev van Ravenswaay/SPL).

Welcome to issue 1!As the new school year starts some of you will be heading

into year 11, the last group to follow the old-style GCSEscience courses; those of you in year 10 will be embarking ona new type of course.

The editors of CATALYST have always sought out interestingstories linked with the science courses to include in themagazine, and help you gain good grades. We also regularlylook at other matters, such as how the science you do at schoollinks into scientific research and the lives of scientists.

We address topical issues in science and often have sectionsabout science in the news. For example, in the April 2006 issuewe covered a story on possible changes in ocean currents, firstaired in the science journal Nature in December 2005. By theApril issue we had secured a group of three related articlesdescribing this research and linking it to your GCSE sciencecourses, as well as suggesting suitable websites for you to findout more.

Nigel Collins

Volume 17 Number 1 September 2006

Editorial teamNigel CollinsKing Charles I School, Kidderminster

David MooreSt Edward’s, Oxford

David SangAuthor and editor

Jane TaylorSutton Coldfield GrammarSchool for Girls

Advisory panelEric AlboneClifton Scientific Trust

Tessa CarrickFounder Editor, CATALYST

David ChaundyFounder Editor, CATALYST

Charlotte CuretonBiotechnology and BiologicalSciences Research Council

Peter FinegoldThe Wellcome Trust

Peter JonesScience Features, BBC

Sarah LeonardScience Museum

Ted ListerRoyal Society of ChemistryFounder Editor, CATALYST

Ken MannionSheffield Hallam University

Andrew MorrisonParticle Physics and AstronomyResearch Council

Jill NelsonBritish Association

Silvia NewtonCheshunt School and Association for ScienceEducation

John RhymerBishop’s Wood EnvironmentalEducation Centre

Nigel ThomasScience EnhancementProgramme

The total mass of all theasteroids is only about3% of the mass of theMoon. The two largest(Ceres and Vesta)account for half of thetotal mass.

1September 2006

Impact Earth

David Sang

GCSE key wordsAsteroidComet

Risk

Figure 1 Orbit of2004 FH

Left: Jupiter providesus with someprotection. Its stronggravity hoovers upmany NEOs, such asComet Shoemaker-Levy 9, which wasobserved as it collidedwith the giant planeton 18 July 1994. Thisartist’s impressionshows that the cometwas pulled apart byJupiter’s gravitybefore impact

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/SPL

On 18 March 2004, asteroid 2004 FH passedbetween the Earth and the Moon. At itsclosest, it was within 43 000 km of the Earth

(that’s just 3.4 Earth diameters). The asteroid was 30 m across, big enough to do serious damage if itreached the Earth’s surface. However, that wasunlikely, for two reasons:• Its orbit did not bring it close enough for theEarth’s gravity to pull it down.• Friction with the atmosphere would have caused itto burn up before it reached the ground.

Small asteroids come as close as this every year ortwo. The unusual thing about the fly-past of 2004 FHwas that astronomers saw it coming and couldobserve it as it went by (Figure 1).

Rocks from spaceAstronomers keep an eye out for any object in space whose orbit may bring it within 50 million kmof the Earth’s orbit. Such space rocks are known asnear-Earth objects (NEOs). There are two types:• Asteroids: rocky lumps, mostly in orbit betweenMars and Jupiter.• Comets: frozen balls of dust and ice whichapproach the Sun from orbits far out in the solarsystem.

The way in which the solar system formed explainswhy these two types of object exist. A swirling cloud ofdust and gas collapsed under the pull of its own

Astronomers say that, one day, a giant rockfrom space will collide with the Earth andcause mass devastation. This could lead to theextinction of many species, including humans.Is there anything we can do to prepare forsuch an impact?

Earth

Moon

2004 FH

gravity. The Sun (mainly hydrogen) formed at thecentre. The planets formed from dust and gas circu-lating round the Sun. The closest planets (Mercury,Venus, Earth and Mars) are rocky, because theirtemperatures are too high for gases to condense. Theouter ‘gas giant’ planets, particularly Jupiter andSaturn, are made of frozen gases.

Another rocky planet tried to form between Marsand Jupiter. However, the gravitational pull of massiveJupiter prevented it from becoming a planet, and sothe asteroid belt was created. Comets formed furtherout in the icy depths of space.

Occasionally, asteroids jostle one another, and onemay be pushed out of the belt so that it plummetsfurther in towards the Sun. If its orbit crosses that ofthe Earth, it may become an NEO (Figure 2).

It has happened beforeThe Earth has been hit by NEOs before (see Box 1).We know this because impact craters can be seen in anumber of places. Among the most famous is MeteorCrater in Arizona. Over 1 km wide and hundreds ofmetres deep, it has been dated to 49 000 years ago. Itis estimated that the cause of this crater was a lumpof iron and nickel about 40 m across, moving atabout 25 km/s. That’s a lot of kinetic energy,equivalent to 20 million tonnes of TNT!

Such craters on Earth are rare. However, theMoon’s surface is covered in craters. The difference isthat here on Earth, craters are eroded by wind andwater. In addition, the movement of tectonic plateshas resurfaced the Earth over millions of years, hidingthe evidence of ancient impacts. But the Earth’sstronger gravity means that it must have been hit witha greater frequency than the Moon.

NEO scaresThe effect of an NEO impact depends on its size (seeTable 1). It is only within the last two decades thatastronomers have established programmes to trackNEOs. You may have heard about potential hazards inthe media. The usual pattern is something like this:• Astronomers announce that they have spotted anNEO whose track might bring it into collision withthe Earth.

2 Catalyst

Figure 2 NEO orbitfor 2002 MN

EarthVenus

MercuryMars

2002 MN

l Visit http://neo.jpl.nasa.gov/neo todownload a multimediapresentation on NEOs.

l You can download amovie showing orbits ofknown NEOs at http://szyzyg.arm.ac.uk/~spm/neo_map.html

This artist’s impression shows an asteroidheading for Earth. A spacecraft is aboutto collide with it, deflecting it from itshazardous path. No one knows if thiswould work; it might simply smash theasteroid into many fragments whichwould then collide with Earth

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• After a few weeks, the NEO’s orbit has beendetermined more accurately; astronomers announcethat it is very unlikely to strike Earth.• The media declare that this was a scare story putabout by astronomers, perhaps to justify theirresearch programmes.

Such media criticism is a bit unfair. Like all observa-tions of moving objects, first measurements have alarge degree of uncertainty. As an NEO moves acrossthe sky, its track can be determined with greaterprecision. Should astronomers keep quiet when theyfirst become aware of a possible impact?

The hazard associated with an NEO is representedby its position on the Torino scale (see Box 2).

Deflecting NEOsDr Alan Harris is a UK scientist based at the GermanAerospace Centre in Berlin. He is chairman of aproject called NEOMAP (NEO Mission Advisory

Panel), which has been looking at what we might do ifwe detect an NEO heading our way. He describes theproblem we face:

If you think about the chain of events betweendetecting a hazardous object and doing somethingabout it, there is one area in which we have noexperience at all and that is in directly interacting withan asteroid, trying to alter its orbit.

Various methods of deflecting an asteroid havebeen proposed, but we do not know enough aboutasteroids to decide what would be best. The DonQuijote mission has been proposed to the EuropeanSpace Agency (ESA) to rendezvous with an asteroidand find out more. Dr Harris thinks this is important:

Don Quijote has the potential to teach us a great deal,not only about the internal structure of an NEO, butalso about how to mechanically interact with it. DonQuijote could provide a vital missing link in the chainfrom threat identification to threat mitigation.

Don Quijote will consist of two spacecraft. The firstwill make preliminary observations of the target aster-oid; the second will impact with it, so that the first canmeasure the effect on the asteroid’s orbit. ESA willmake a final decision on the target asteroid in 2007.

David Sang writes textbooks and is an editor of CATALYST.

3September 2006

Box 1 Did a comet kill off thedinosaurs?In 1980, Luis and Walter Alvarez published a papersuggesting that the extinction of the dinosaurscould be traced back to an asteroid impact 65 million years ago. Palaeontologists hadestablished that dinosaurs and many other speciesbecame extinct at that time, but the cause wasunknown. The father-and-son team examined rocksat the boundary between two geological zones, theCretaceous and Tertiary. They found a thin layer,called the K/T boundary, containing two elements— iridium and osmium — which are rare on Earthbut common in asteroids. They deduced that anasteroid about 10 km across had collided with theEarth; it evaporated, so that its material was spreadaround the Earth.

The impact must have produced a mass of dustwhich darkened the skies, causing freezingtemperatures for several years, and this resulted inmass extinction. Fortunately for us, some mammalspecies survived.

Ten years after the Alvarez paper, a giant crater on Mexico’s Yucatán peninsula was identified from observations by a space shuttle. Mostscientists now accept this theory of dinosaurextinction, although some believe that otherfactors, including volcanic activity, may have been involved.

Box 2 The Torino scaleThe Torino scale runs from 0 (minimal chance of impact) up to 10 (globalcatastrophe likely).

Figure 3 shows how the rating of an NEO depends on its energy and itsprobability of colliding with Earth. Kinetic energy is given in megatonnes ofTNT equivalent (1 MT = 4 × 1015 J approximately).

Box 3 Taking chancesYou are more likely to die as a result of a near-Earthobject impact than in an air crash — true or false?It’s probably true. Air crashes are rare events, andcause only 1 in 30 000 deaths. (Road accidentscause about 1 in 100 deaths.) NEO impacts areeven rarer, but the death toll could be vast, soscientists estimate that the chance of an individualdying is about 1 in 10 000.

Table 1 The effect of NEO impacts

Diameter of NEO Effect of impact< 50 m Disintegrates in atmosphere

< 500 m Local damage around impact site> 1 km Worldwide effects

> 10 km Mass extinctions

108

(5 km)Global10

8

9

76

2

1

0

3

4

5Regional

Local

No consequence

(1 km)

(100 m)

(20 m)

10–8 10–6 10–4 10–2 >0.99

105

100

1

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etic

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T)Collision probability

A near-Earth objectwhich strikes the Earthis more likely to land inthe sea than on solidground, simply because70% of the Earth’ssurface is ocean.

l Spaceguard UK is theBritish arm of aworldwide network ofastronomers concernedwith the hazards posedby NEOs. Go to www.spaceguarduk.com/sguk.htm to find out more.

Figure 3 Torino scale

E very part of this chain offers exciting prospectsfor a career, from food research and developingnew products, to packaging design or pro-

duction engineering. There is also plenty of room forentrepreneurs in the food industry so you could set upyour own food company — supermarkets, restaurantsand cafés are always demanding new and innovativefood and drink products.

Be what you want to be…New product developmentThis is the ‘lifeblood’ of the industry. Product devel-opment is a team-based activity involving develop-mental chefs, food scientists, nutritionists, marketingpeople to conduct consumer research, technologiststo design the production lines, and packagingdesigners.

Quality managementQuality managers monitor the quality and safety of food ingredients and food products while theyare made and transported. They include laboratorystaff, microbiologists, hygiene managers and qualitycontrollers.

Environmental healthEnvironmental health officers (EHOs) are employedby local councils to inspect food factories, shops,restaurants and catering outlets to ensure that foodstandards and hygiene are maintained. Local councilsusually recruit trainee EHOs with A-levels. Look upenvironmental health on your local council website.

BuyingSupermarket chains employ buyers to visit foodproducers as part of their quality control. Buyers haveexperience in a particular area of food technology andwork closely with food producers to develop newproducts and new food ranges. Some buyers get totravel, perhaps visiting salmon producers in Canadaor spice manufacturers in the Far East.

NutritionNutritionists are usually graduates with a wideknowledge of healthy eating and diet-related issues,such as obesity, heart disease and coeliac disease.Many are employed by health authorities, clinics and

4 Catalyst

Your future Food technology

The food and drink industries are part of achain linking farming and growing through tofood processing, manufacture and finally tothe sale of food in supermarkets andrestaurants. Dr Ken Spears tells us aboutsome of the many career areas in foodtechnology.

Box 1 Did you know?l The food and drink industry buys two-thirds ofall fresh produce grown in the UK.l As well as shops, there are over 30 000 UKbusinesses involved in food and drink.l The food and drink industry employs over650 000 people in the UK; 200 000 extra employeeswill be needed by 2012 to fill vacancies.l The food and drink production industry has anannual turnover of £69 billion — 6% of the UKeconomy.l Young people can expect starting salaries of£15–£18K, and graduates can expect to start on£20–£25K. Senior food scientists can earn £65K or more.

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There are some 30 000businesses in the UKinvolved in food anddrink, not includingshops andsupermarkets.

government agencies, but companies also employtheir own nutritionists to give advice on healthy foodproduction and to their customers.

Food researchGovernment research agencies carry out research to ensure good nutrition and food safety, and as part of a European team monitoring food quality.Careers in food research require scientific knowledgeand skills at all levels, including laboratory assistantsand technical officers. The research agencies havelibraries and so also need librarians and informationresearchers.

QualificationsThe above examples should convince you that there is more to a career in food than putting cherries onthe top of cakes. So how do you start your career?Your GCSEs and A-levels provide the basis for a rangeof higher qualif ications, skills and work-basedlearning. An interest and enthusiasm for science andpractical technology are useful.

National Vocational Qualifications (NVQs)Some areas of the industry require NVQs. You canstudy for these while you are at work, but you also needto spend some time in a college of further education.

National DiplomaYou can complete a National Diploma by part-time orfull-time study. This can be combined with work-based learning and is intended for people interested inmanagement. National Diplomas may be acceptedfor entry to degree programmes.

DegreesThese involve full-time study at a university. Someuniversities offer ‘sandwich’ courses where you spenda year on an industrial placement with an employer,like Cath Harris did (see Box 2.)

Dr Ken Spears is a food technologist who has industryexperience. He has taught food technology in schools and atSouth Bank University.

Marks and Spencerreformulates each of itsthousands of differentfood products every3 years.

5September 2006

Box 2 A case studyThe Institute of Food Science and Technology(IFST) is the professional body of food scientistsand technologists. Its website (www.ifst.org) hasa section on careers and training where you canfind out what people like Cath Harris do.

Cath studied food quality, product develop-ment and nutrition at the University of Plymouth.After her degree she became a senior purchaser.Her job includes product quality, pricing,delivery deadlines and maintaining goodsupplier relationships.

I find it challenging to experiment with foodgroups and flavours. To make them blend well intaste and texture is very satisfying but the resultcan be hideous if you get it wrong! My interest inexperimentation is related to product

development within the food industry and isprobably the most proactive and exciting part ofthe sector.

It is essential to understand the bacteria in foodsubstances and the effects they can have in foodpreparation, final serving and the shelf life of afinished product. My interest was stimulated bythe microbiological part of my degree course.

During my work placement I joined my currentcompany as a member of the quality assuranceteam. The company creates fine frozen seafoodand vegetable-based products for the foodserviceindustry. I worked within the factoryenvironment and learnt about production andpeople management, and gained a vast amountof technical knowledge.

Left: Researcherdeveloping food withhigh mineral, vitaminand protein content

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Box 3 Useful websitesImprove Ltd is the Sector Skills Council for themodern food and drink industries:www.improveltd.co.ukThe Grocer magazine website has a careerssupplement: www.careersinfoodanddrink.co.ukThe trade journal Food Manufacture also has auseful website: www.foodmanufacture.co.ukOther useful websites include:l Food and Drink Federation: www.fdf.org.ukl The British Retail Consortium (BRC):www.brc.org.ukl Meat and Livestock Commission:www.mlc.org.ukl The Biscuit Cake Chocolate and ConfectioneryAlliance (BCCCA): www.bccca.org.uk

Cath Harris

GCSE key wordsTesting medicines

Diseases happen when things go wrong in thebody. Once scientists begin to understand theproblem they can search for medicines that

will help sufferers. They investigate any potentialmedicine to show how effective it is and to find out ifit is likely to have any harmful or unpleasant sideeffects.

Laboratory testsThe effects on cells of a potential new drug are inves-tigated using tissue cultures of human or animal cells.Some tissue cultures use fresh tissue samples, butmost come from well-established laboratory cellstrains. The cell cultures receive various doses of thetest substance and its effects are monitored. If asubstance harms abnormal cells, such as culturedcancer cells, or stops viruses infecting cells, it could beuseful. At the same time, scientists check that the drugdoes not affect normal cells.

Computer modellingScientists use what we know about the complex interactions of the human body’s biochemistry tomake computer models of body systems. New drugsare tested in these systems to see how they affect thenatural variations of body chemistry in the humanpopulation.

These systems can show unanticipated side effectsand interactions between the new substance beingtested and other drugs that people might be taking, as

Animals benefit fromtesting involving otheranimals in thedevelopment ofveterinary medicines.

6 Catalyst

Jane Taylor

Testing new medicinesNew medicines cannot be prescribed untilthey have been tested to see if they are safe forpeople to take. This article outlines theprocesses involved, from laboratory tests toclinical trials.

Right: The short lifeand plentifulreproduction of miceallow scientists tomonitor impacts onlife span and the nextgeneration To

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New medicines mightreplace a defectiveenzyme product, changea biochemical reaction,help substances tomove in or out of cells,kill some cells orencourage other cells togrow.

well as with substances such as alcohol and coffee.Undesirable interactions can be ‘designed out’ by manipulating the structure of the new drugmolecule. Computer modelling can even producedetailed information that cannot be generated byexisting experiments.

Testing on animalsOnce a new drug’s potential for working on diseasedtissues has been tested on cells it is time to see if itworks in a whole organism. Laboratory cell cultureshave a carefully controlled environment with constantsupplies of nutrients. This is different from the envi-ronment in a human body with its varying levels ofnutrients, wastes, hormones and other importantbiochemicals.

Animal tests tell scientists if a drug affects organsother than the target diseased tissue, what theeffective dose and harmful doses are, and if there arelikely to be side effects. Data are collected on howthe new drug is absorbed, spread round the body,changed or broken down by the body’s enzymesystems and excreted, as well as how toxic it is.

Two species of animals, including one which is not arodent, must be used for such tests. Mice are oftenused. Some strains of laboratory animals suffer someof the same diseases as humans so some new drugscan be tested for their effects on the actual disease,rather than on healthy animals.

Clinical trialsOnce a drug is shown to be safe and to work in tissuecultures and animals it has to undergo clinical trialson humans. The physiology of other mammals is verysimilar to our own, but there are important differ-ences. It is only when the drug is in the whole humansystem that scientists can see its true effects. Somecomplications are seen for the first time when realpeople use the drug. Some drugs are given to healthyvolunteers first, but they are usually tried on patients.

In more economically developed countries there areethical guidelines about which patients can be askedto take an experimental drug, and they must agree tobeing treated with it. The drug’s use should becarefully monitored and any side effects recorded. Thedrug must have a good record in clinical trials if it is togain a licence for use.

Blind and double blind trialsSometimes we really want our experiments to workand unconsciously interpret our results to f it ourexpectations. If scientists expect a new drug to relievesymptoms they will tend to view what it does in afavourable light.

Data gathered from trials must be assessed objec-tively so potential new drugs are tested using doubleblind trials. The doctors who are administering a drugunder trial do not know if the medicine they are givingcontains the new drug, the usual medicine or aharmless substitute (a placebo). Doctors assessingthe patients’ symptoms after the course of treatmentdo not know what medicine the patients received.Who had what medicine is only revealed when the fullresults are analysed.

Jane Taylor teaches biology and is an editor of CATALYST.

l Use the internet toinvestigate the latestposition on the buildingof the new researchlaboratory at OxfordUniversity.

7September 2006

Box 1 Useful websitesl Log on to www.abpi-careers.org.uk to exploremore about the processes involved in developingand testing new medicines, as well as about thescientists involved.l You can find out about a number of differentclinical trials by logging on to www.bctu.bham.ac.ukand clicking on ‘Current trials’.

People may reportfewer symptoms, or lesspain, after they havebeen taking what theythought was a medicine,even if it did not containany active ingredients.This is known as theplacebo effect.

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Drugs must be tried out onreal patients before scientistscan be sure they work safely

Alchemy

One of the aims of the alchemists was todiscover and use the magical Philosopher’sStone, which was supposed to change

worthless metals into gold. The alchemists thoughtthat this was possible because they believed that everysubstance was a combination of the four elements:earth, air, fire and water.

GoldGold was a key material in alchemy. Its coloursuggested the Sun, and its complete resistance tocorrosion marked it out as something special. Goldwas the only metal that could not be dissolved awayby ordinary acids. It even resisted concentrated nitricacid. Thus, acids could be used to distinguish betweenreal gold and a mere yellow alloy such as brass.

Gold also had symbolic significance as the metal ofkings, princes and emperors because it representedtheir nobility — their supposed immunity from thebaser concerns of the common people. Alchemiststhought that turning the base metal lead into thenoble metal gold was simply a matter of dissolvingaway the unwanted qualities and nourishing the ‘seed’of gold. Like all metals, gold was thought to besomehow born from Mother Earth. This process wasbelieved to be like the normal plant cycle of life anddeath followed by regeneration.

The ideas behind alchemyThe complex ideas underlying alchemy were a mixtureof detailed practical knowledge and ancient religiousand mystical beliefs, as well as the thoughts of Greekphilosophers.

The planets played an important part in this, andmany substances, especially metals, had astrologicallinks (see Table 1). Unsurprisingly, the Sun repre-sented gold, and the Moon silver. According toalchemical theory these two metals also representedcomplementary opposite ‘masculine’ and ‘feminine’characteristics, like the ‘Yang’ and ‘Yin’ of Taoism,which are linked to day and night, Sun and Moon andso on.

8 Catalyst

GCSE key wordsDistillation

Scientific methodAcids

Corrosion

Alchemy is the study of eternal life, salvation,and the answers to the ultimate questionsabout life, the universe and everything. Itf lourished for more than 1500 years until, inthe late 1600s, the beginnings of modern,scientific chemistry edged it aside. But whatwas alchemy and who were the alchemists?

John Tucker

Box 1 Henning BrandtHenning Brandt was a German alchemist of themid-seventeenth century. Brandt discoveredphosphorus accidentally, about 100 years beforeJoseph Wright’s famous picture of him waspainted. It seems that he had an idea that gold andthe yellow colour of urine were connected in somemysterious way.

While heating the solid residues he had got fromevaporating several buckets of stale urine withpowdered charcoal he found that phosphorus,glowing and burning, distilled from the flask. Hebelieved that he was on the threshold of discoveringthe Philosopher’s Stone. He wasn’t, of course, andeventually he sold the recipe, which he had keptsecret for some years, to cover his debts.

We still use theexpression ‘the acidtest’ to mean anespecially critical test ofgenuineness.

‘The Alchymist, In Search of thePhilosopher’s Stone, Discovers Phosphorus,and prays for the successful Conclusion ofhis operation, as was the custom of theAncient Chymical Astrologers’.This famouspainting by Joseph Wright of Derby, from1771, almost certainly portrays HenningBrandt, a German alchemist of the mid-seventeenth century

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Practical chemistsAlchemists were the chemists of their time. They usedthe same methods of extraction and purification asyou will have encountered in the laboratory: filtration,distillation and crystallisation, for example. Like you,they heated and mixed substances to see what wouldhappen. They used acids and alkalis, dissolved thingsin water, and ground solids up into powders to makethem react more efficiently. Their pieces of apparatusmay look rather odd, but the alembic (see Figure 1),for example, was basically for distillation.

Alchemists did thousands of experiments and thenrecorded their observations. However, the languagethey used was often deliberately obscure so it isdifficult for us to understand.

Their desire to get at the essence of things ledalchemists to distil plant and animal products. The

essences they produced might be oils, perfumes, orliquids with medicinal properties known as elixirs.One such liquid was alcohol, which was thought to bein some way a spirit. Hence the modern use of theword ‘spirits’ to indicate a drink with a high alcoholcontent, like whisky or brandy.

Alchemists invented furnaces for heating mixturesstrongly and melting metals, and the water bath, orbain-marie (named after a famous female alchemist,Mary the Jewess), for gentle heating over a longperiod. They invented pieces of apparatus which werethe forerunners of modern laboratory glassware, andthey discovered many useful chemicals, like the threemineral acids.

9September 2006

Table 1 Astrological symbols for metals

Substance Planet Symbol

Gold Sun

Copper Venus

Mercury Mercury

Iron Mars

Vapour condenseson cool surface

Liquid runs downinto this channel

Mixtureheatedhere

Distillate runsout here

Heat Figure 1 An alembic

Mercury, a liquid metal, was named‘hydrargyrum’, ‘water-silver’; hence thesymbol Hg.

Robert Boyle and IsaacNewton werealchemists as well asscientists.

Ben Jonson, acontemporary ofShakespeare, wrote hisplay The Alchemist in1610. Its plot involvedfake alchemists.

Key substancesdiscovered or refined bythe alchemists includeglass, the three mineralacids (hydrochloric,nitric and sulphuric),‘sal ammoniac’(ammonium chloride),alcohol, alum,phosphorus and alkalis.

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Left: Two earlysixteenth-centuryalchemists standingbehind alchemicalapparatus designed todistil liquids

Alchemy was not a scienceAlchemy was not a science with a rational set oftheories tested against the experimental evidence.Alchemists certainly had theories, but they tended totry to make the experimental facts f it them ratherthan the other way round. They made little progressbecause they stuck to a pre-existing set of theoreticalideas and were reluctant to communicate theirfindings publicly. These two failings, as we would seethem, were to them the whole point of alchemy.

Alchemical authoritiesAlchemy looked backward to the ideas of ‘author-ities’: learned men and women who, it was thought,had possessed a knowledge lost long ago. This couldonly be recovered by devotion to their ideas andattempts to rediscover their ‘secret’. Present-dayexpressions like, ‘The secret of successful revision is…’hark back to this attitude of mind. By ‘secret’ or ‘art’we mean a technique passed on by word of mouth, orperhaps by apprenticeship to a more experienced andwiser person.

Alchemical secretsAlchemists thought there was a bright and wonderfulsecret at the heart of alchemy. This secret was not tobe revealed to ordinary people who might not havethe strength of character or nobility to stop themfrom abusing that knowledge.

It is worth noting that in the twentieth centurymany of the scientists who worked on the Los Alamosproject were worried about the potential evil uses of atomic energy. Today, we are concerned aboutthe potential misuses of genetic engineering. Thedifference is that these are, more or less, openlydebated and that publication and peer review allowscientists to share knowledge and keep each other upto the mark. Thousands of alchemical experimentswere needlessly repeated time and again.

Alchemy and chemistryWas alchemy the beginning of chemistry? Opinionsvary, but although alchemy contributed nothing tothe all-important theoretical basis of modern science,it did produce or isolate a number of key substancesfor the first time. Alchemists also developed practicaltechniques which are still being used in the twenty-first century.

John Tucker teaches chemistry at St Edward’s, Oxford and is anexaminer.

10 Catalyst

Box 2 The lure of goldBeing an alchemist was expensive: there were allthose unusual pieces of glassware to be paid for aswell as rare, highly priced chemicals from theOrient. To be one, you needed either a wealthypatron or a private income. The famous painting byWilliam Fettes Douglas shows an old manexplaining the significance of a flask of gold-coloured liquid to a rich nobleman or merchant.

The lure of unlimited quantities of gold allowedconmen to swindle greedy people by a variety ofsimple tricks. One scam was to coat a small pieceof gold in black wax so that it resembled anordinary metal. During a long ritual, this blacklump was put into a crucible in the furnace, alongwith the last few drops of the all-important elixir.The wax would melt, of course, and burn away,leaving the ‘miraculous’ piece of gold. Suchcharlatans gave alchemy a bad name; although itdid not help matters that genuine alchemistssometimes resorted to similar frauds.

Box 3 Alchemy websitesLook up the following websites to find out moreabout alchemy:http://en.wikipedia.org/wiki/Alchemy www.levity.com/alchemy/index.htmlwww.pbs.org/wgbh/nova/newton/legacy.html

In Britain, it was notunusual for a clergymanto be a secret alchemist.Very likely he wouldhave inherited wealthand could subcontractcurates to do his parishduties, leaving him withplenty of time to pursuethe ‘Divine Art’, as itwas known.

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During the SecondWorld War, the topsecret Los Alamosproject built the USA’sfirst atomic bombs.

Above: ‘TheAlchemist’ by WilliamFettes Douglas

T extbooks and magazines, like CATALYST, arechecked by their authors, editors and technicalreviewers to ensure that they are accurate.

They explain when an ethical or controversial issue isbeing considered, rather than stating it as hard fact,and give you some of the differing points of view.

Some websites are also rigorously checked (wecheck the ones we recommend to you), but anyonecan set up a website. For example, a site you visit aftersearching for a scientific term on Google could bebased in a university or could be your next doorneighbour’s. You cannot assume that anything on it isaccurate or even halfway correct unless you havethoroughly checked its credentials. Here are somestrategies to adopt when looking at a website.

(1) Visit the home page• When was it created and last updated? Sciencechanges fast.• Whose site is it? Are they experts? Are they biased?Are they a pressure group, a business or do they havea vested interest? Pressure groups may only presentone side of an argument or sensationalise theirviewpoint. On the other hand, such sites can be usefulfor exploring controversial issues, such as those raisedby animal experimentation.• Do the links work? If not, the site is old and is notbeing maintained.• Is it at the right level? You want more accuracy onnutrients, for example, than a health food supplierneeds but not a university course. Some companywebsites can be informative, but most are too general.If they can’t spell the terms correctly they are not foryou.

(2) Look at the web addressWebsites that you can trust include libraries andwebsites ending:• ac.uk — a UK university or government-fundedresearch organisation• edu.au — an Australian university• edu — a US university• org — a website ending with this is a reputableorganisation and should be factually correct

For example, the web address of The Royal Societyis www.royalsoc.ac.uk and the British Trust forOrnithology is www.bto.org. Many of these sites havelinks to other reputable sites that you can follow.

A great resourceIn summary, the internet is awonderful resource, but alwayslook critically at anything that yousummon up on screen.

Box 2 Exam board websitesThe internet provides access to examination boardwebsites (see below), where you can find thespecifications for your course, past examinationpapers and mark schemes. These examinationboard sites may offer useful support materials withcoursework. You can also read examiners’ reports,which include what people tended to get wrong inrecent examinations — check that you know andunderstand these things!l England: www.aqa.org.uk, www.edexcel.org.uk,www.ocr.org.ukl Wales: www.wjec.co.ukl Scotland: www.sqa.org.ukl Northern Ireland: www.ccea.org.uk

Box 3 Science in the newsThe internet provides an extraordinary window intothe wider world of science and offers an excellentway to gain access to a wide range of topicalinformation and breaking science news. This couldcome in especially handy for those of you doing thenew GCSE science courses.

You could:l download the latest images from the satelliteorbiting Venus (www.esa.int/esaMI/Venus_Express)l download and listen to lectures delivered recentlyby famous scientists (www.royalsoc.ac.uk)l catch up on the latest information about bird flufrom the World Health Organization(www.who.int)

Box 1 LinksIt is worth looking at whether othersites have made links to the site you havefound. You can check this out in Google by entering‘link:webaddress’ in the search box. If the linked sitesare reliable ones, it is unlikely that they will makelinks with sites with poor credentials.

11September 2006

Evaluating websites

www.quick.org.uk/menu.htm is an excellentwebsite offeringcomprehensive adviceon how to evaluatewebsites.

Improveyour grade

The internet can be useful for all sorts of reasons during yourGCSE science course, but should be used with caution.

Read ‘A life in science’on pages 12–13 to findout about the origins ofthe World Wide Web.

In the late 1980s Tim Berners-Lee was working atCERN, a large, international particle physics lab inGeneva where thousands of scientists and techni-

cians work collaboratively. As in many branches ofscience, experiments in particle physics generate largeamounts of data in very short spaces of time, andthese have to be stored and analysed on computers.Tim devised the Web to allow his colleagues to accessdata at the click of a mouse, but he could also see theadvantages of such a system for people in manydifferent walks of life.

The internet already existed when Tim invented theWeb (see Box 1). Tim realised the need for standard

approaches for identifying resources on the Web, andfor sending information from one computer toanother (see Box 2).

Early daysTim Berners-Lee grew up in southwest London. Hisparents were involved in developing early computers.He wasn’t sporty; he preferred toy trains, and later theelectronic systems that control them. He went toOxford University to study physics. He and a friendwere banned from the university computer after theywere caught hacking.

After graduating with a BSc degree, he worked inindustry before moving to CERN in 1984. There, hedevised computer systems for controlling experiments

12 Catalyst

A life in science

TBL @ WWWToday, most readers of CATALYST have easyaccess to the World Wide Web. Ten years ago,that was not the case. Tim Berners-Lee, aBritish scientist, came up with the idea of theWeb in the late 1980s and set up the firstserver for it in December 1990.

Box 1 The internet and the WebThe internet existed before the World Wide Web —they are two different things. The internet is the system which allows two computers tocommunicate when they may be on opposite sidesof the world. The Web is a system for locating andtransferring information (text, data, images etc.)over the internet. E-mail is an example of anothersystem for transferring information over theinternet.

Box 2 WWW essentialsWhat does it take to make a web linking computerusers around the world?Hypertext Uses links to allow the user to jumparound within a document, or from one documentto another. (You can create links in a documentusing a word-processing program such asMicrosoft Word.)HTML Hypertext mark-up language — the codeused to send the words, pictures, sounds etc. whichmake up a page of hypertext.Resource identifiers The addresses which tell thesystem where to find the pages you are looking for.Clients and servers Your computer is a client; itsends out requests to the network of servercomputers via your internet service provider, andthey send back the pages you require (Figure 1).

The UK is one of theworld’s top tencountries for internetusage. In January 2006,there were an estimated37 800 000 internetusers in the UK, 63% ofthe population.

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and handling data. This led him to see the need forthe Web. He came up with the idea of giving every‘document’ a universal document identifier (UDI). A document might be text, data, an image orwhatever. Today, these identif iers are known asuniversal resource identif iers (URI); they are thefilenames that start www. and end .html, .pdf, .docand so on.

Today and tomorrowTim is now professor of computing at bothSouthampton University and MIT in Boston. He isalso director of the World Wide Web Consortium, anorganisation guiding the development of the Web.

Perhaps the most impressive aspect of Tim’s inven-tiveness was that he could see the great use the Webwould come to have for millions and even billions ofpeople. He chose not to patent his idea, so that it isfreely available for all to use.

The Web is often criticised because it allows peopleto download violent or obscene images, or evenbomb-making recipes. What does Tim say to this?

People also say how their lives have been saved becausethey found out about the disease they had on the Web,and figured out how to cure it.

I think the main thing to remember is that any reallypowerful thing can be used for good or evil. Dynamitecan be used to build tunnels or to make missiles.Engines can be put in ambulances or tanks. Nuclearpower can be used for bombs or for electrical power.

The Web is a tool for communicating. With the Web,you can find out what other people mean. You canfind out where they are coming from. Let’s use theWeb to help people understand each other.

David Sang writes textbooks and is an editor of CATALYST.

13September 2006

Internet(more servers)

Firewall/router

Clients

Server

Datareply

Requestdata

How many of the following wordscan you find in the grid? Words canrun in any direction. Which of thewords listed below is not in thegrid?

air alchemy

alcohol alembic

bainmarie earth

element elixir

fire gold

iron liquidity

mars mercury

moon philosopher

quintessence spirit

stone sun

touchstone transmutation

water

Answer on page 19.

Puzzle

D I V A N E L I X I R A N

Z L I O R C E L E M E N T

O A O I P N C I B M E L A

U M F G R E L O H O C L A

T O U C H S T O N E C H E

R E H P O S O L I H P I H

O H T R A E Q R E T A W A

N O I T A T U M S N A R T

S N G I B N Y E N O T S N

R U R B A I N M A R I E O

A S O Y R U C R E M O O R

M U L L I Q U I D I T Y I

Alchemical wordsearch

Figure 1 Client–server relationship

Tim Berners-Lee’shomepage(www.w3.org/People/Berners-Lee) includes alink to his blog.

Weaving the Web by TimBerners-Lee is hisaccount of the inventionof the Web.

P lants use water from the soil, carbon dioxidefrom the air, and mineral nutrients such asnitrate, sulphate and phosphate ions, also from

the soil, to make carbohydrates, proteins and lipids(fats). Photosynthesis is effectively a type of chemicalprocess called reduction. Plants release oxygen as partof this process; they also use hydrogen atoms fromthe water to make sugar.

The materials made by a plant form its biomass.Plant biomass is the immediate source of energy forall living things, not just animals but also the plantitself. Respiration releases the energy from carbohy-drates. This process is the converse of photosynthesisand can be thought of as an oxidation process. Itrequires oxygen and releases carbon dioxide gas tothe atmosphere; hydrogen atoms are also transferredback into the other by-product, water.

Combustion is also an oxidation process — torelease the energy from a fuel, oxygen is needed aswell as the fuel. Carbon dioxide and water are

produced. Combustion therefore has the samestarting materials and end-products as respiration:

organic matter + oxygen → carbon dioxide + water

Biofuel basicsWhen fossil fuels, such as oil, natural gas and coal, areburned, the carbon dioxide released has been out ofcirculation for a very long time, so any which isreleased in this way is in addition to that maintainedby normal carbon cycling (see Figure 1).

When fresh biomass, such as wood or the residue ofcrops, is burned, the carbon dioxide that is releasedwas in the atmosphere recently and is now returned toit. Other plants grown for harvesting as fuel thenutilise this carbon dioxide.

Some crops grow very quickly, producing a lot ofbiomass in a short time (Table 1), and a number ofcrops are grown deliberately for energy production,rather than to provide food. Table 2 lists someexamples.

14 Catalyst

BiofuelsNigel Collins

GCSE key wordsEnergyEthanol

FuelGlobal warming

Burning fossil fuels releases extra carbon dioxide into the atmosphere, which contributes toglobal warming. However, burning renewable biofuels is part of the normal carbon cycle anddoes not contribute to an increase in atmospheric carbon dioxide. This article looks at the waysin which the energy stored in biofuels can be released.

Using vegetable oil asfuel in diesel engines isnot a new idea. RudolfDiesel’s first engineswere built to run onpeanut oil in countrieswhich had nopetrochemicalsindustry.

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Biofuel for carsEach of the energy crops in Table 2 can be convertedto a liquid fuel that can be used to power vehicles. Themain way in which this is produced is by fermen-tation, followed by distillation, to produce ethanol.The crops contain sugar, either as individual sugarmolecules or in the polymers, starch or cellulose.Sugar and starch are used in most instances:• stage 1: starch/cellulose is broken down to sugar,involving the use of acid• stage 2: sugar → ethanol + carbon dioxide, usingyeast

15September 2006

FUEL

FUEL

Long ago

Carbondioxide+ water

Extracarbon dioxide

(+ water)

Normal carbon cycle

Carbon cycle involving fossil fuels

Present day

Global warming Photosynthesis

Fossil fuel + oxygen

Biofuel + oxygen

Biomass + oxygen

Combustion

Combustion

Respiration

Figure 1 The carbon cycle and fuels

Table 2 Energy crops

Energy crop Examples Fuel use Alternative uses

Cellulose/ Wood, straw Combust directly as Digest cellulose to sugar and use this to make lignin crops heating fuel ethanol, which can be blended with petrol

Starch crops Barley, wheat, maize and Use to produce ethanol, which Straw from cereals can be burnedrice seeds, potatoes can be blended with petrol

Sugar crops Sugar cane, sugar beet Use to produce ethanol, whichcan be blended with petrol

Whole plants Maize, Miscanthus, reed canary Combust directly as Convert to methanol or ethanol, which can begrass, coppiced willow, poplar heating fuel blended with petrol

Oil crops Sunflower, olive, palm, Combust directly as Add to transport fuel to make biodieseloilseed rape heating fuel

Table 1 Fast-growing biomass crops

Annual yield of dry matter

Type of plant (tonnes per hectare)

Wood produced by shortrotation coppicing of 10 willow or poplar

Giant grasses, such as Miscanthus, reed canary 60grass or switchgrass

Another way to make abiofuel is to use bacteriato decompose organicmaterials underanaerobic conditionsand release methane, aninflammable gas. Thisbiogas, produced bymicrobial respiration,can be used as a fuel topower the generation ofelectricity in sewageworks, for example.

Although many dieselcars can run onbiodiesel, some withparticular makes ofinjector pump cannot —so don’t try puttingbiodiesel in the familycar without thoroughresearch!

l Log on tohttp://bioenergy.ornl.gov/papers/miscanthus/miscanthus.html to findout more about a fast-growing biomass crop.

The ethanol can then be blended with petrol(usually between 5% and 22% ethanol). Brazil has over300 distilleries, and the fuel derived from sugar canethere is called gasohol. In the USA, Spain and France,maize and other cereal crops are used as the feed-stock. The organism involved in ethanol production isoften a variety of yeast; experiments are also beingconducted in Canada and Scandinavia with othermicrobes that can digest woody material, releasingsugar from lignin and cellulose.

The other plant product that can be used as a fuel is the oil produced by plants within their seeds orfruits. The seeds, such as those of sunflower, rape or palm, or fruits, such as the olive, are crushed torelease the oils. The oils can be used in two ways. They can be added directly to diesel fuel as asupplement or they can be converted to biodiesel(see Box 1).

Nigel Collins teaches biology and is an editor of CATALYST.

16 Catalyst

Box 1 Biodiesel: a case studyWas that a whiff of doughnuts when that car went past? Maybe the driverwas someone like Steve Dewar. Although Steve has an ordinary diesel-engined car it can also use biodiesel. Steve uses waste cooking oil from alocal café to make biodiesel. Chip shop and curry restaurant oils are notsuitable, but filtered doughnut frying oil is fine.

Waste cooking oil is normally sent to landfill sites or put down drains. Itwas used for pet food, but since there is a risk that it could contain animalproducts it can no longer be used for this. So, as well as helping his pocket,biodiesel also reduces the waste problem — something that Steve caresdeeply about.

Steve learned about biodiesel from a friend and researched how to make iton the internet. One big advantage of biodiesel in the past was that it costless than conventional diesel. It also has a higher cetane rating (a measure ofhow easily it ignites), produces cleaner emissions — no oxides of nitrogen,sulphur dioxide or particulates — and makes car engines run better.

The price advantage has almost disappeared because home biodieselmakers now have to pay more fuel tax on their oil — 47p per litre.Commercial companies which can prove their biodiesel meets Europeanstandards pay less fuel tax, but there aren’t many commercial producers yet.Biodiesel is popular in Germany and there is a growing band of backyardbiodiesel producers in the UK.

The science of making biodieselWaste cooking oil consists mainly of triglycerides. The process uses methanoland sodium hydroxide to split the triglyceride molecules into glycerol andfatty acids. The fatty acid products are the fuel element. Glycerol can becomposted, recycled and used to make other products.

Making biofuel

l Log on towww.greenfuels.co.ukand click on biodiesel.Look at both sections.You can download aPDF that describes theprocess of makingbiodiesel in detail.

A small-scalebiodiesel plant

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Ltd

Caustic soda inputfunnel (raw material)

Methanol hand pump

Methanol (raw material)

Catalyst premix tank Processor tank Wash tank

Tank heater band

Input oil (raw material)

Maintaining your blood pressure is animportant part of keeping your body inbalance. Blood is put under pressure when it

passes through your heart. The main function of theleft ventricle when it contracts is to pressurise bloodso that it is forced through the blood vessels whichserve the organs of your body (Figure 1). The tinycapillaries that distribute blood through your tissuesand organs have a very small diameter and so offer ahigh resistance to the flow of blood through them.Your heart needs to work hard to provide enoughpressure to push blood through the miles and miles ofcapillary beds.

Inside a capillary bed in an organ, blood pressure ispart of the mechanism that causes water to leave the blood and enter the tissues carrying nutrients,

Blood pressure Jane Taylor

Have you ever fainted? Fainting can be theresult of a sudden drop in your bloodpressure, which is often part of a shockreaction. Read on to find out more about howand why your blood pressure may vary.

17September 2006

GCSE key wordsHeart

CirculationBlood pressure

Valvesforcedopen

Aorta

Blood under highpressure (120 mmHg)

Contracting muscle pushes blood throughvalves into aorta

Closed valveprevents backflow

Atrium

Ventricle

Tendons stopvalves turninginside out

Figure 1 One half of aheart during ventricularcontraction

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Above: A capillary inthe liver. Its smalldiameter (note thesize of the red bloodcells) creates a highresistance to bloodflow

hormones and other useful substances (Figure 2). Bythe time blood has travelled to the end of a capillarybed it has lost much of its volume and pressure. Thepressure of fluid in the tissues is now higher thanblood pressure, so water can return to the blood fromthe tissues by osmosis.

Measuring blood pressureYour blood pressure is given as two f igures, forexample 120 over 80 mm of mercury (mmHg).Although we should use pascals to measure pressure(the reading above would be 16 over 10 kPa), thegeneral public is more familiar with the older units.

A doctor or nurse measures your blood pressureusing a sphygmomanometer. Usually a cuff iswrapped round your upper arm to measure thepressure in the main artery supplying your arm. Thisartery is one of the first branches from the aorta sothe pressure is high.

As the cuff is inflated the pressure of the air inside itpushes on the artery and stops blood flow through it.The air pressure is then reduced slowly. When the airpressure is low enough for blood pressure to forceblood through again the nurse can hear the bloodflow. The pressure can be read off the scale. This givesthe higher f igure (120 in the example above). Itrepresents the pressure of the blood as the leftventricle contracts to push blood out of the heart.This is the systolic pressure.

The lower figure (80 in the example above) is whenthe nurse can no longer hear the flow. It is the bloodpressure in the arteries while the heart is relaxed andfilling with blood. This is the diastolic pressure. Manyhospitals now use digital blood pressure meters whichare thought to be more accurate than a nurse’sjudgement of the flow.

Normal blood pressureHealthy people have blood pressures around thefigures given above (120/80 mmHg). If you need tohave your blood pressure taken you may be asked tosit quietly for a while beforehand because when youare active your blood pressure rises slightly. Duringactivity your body produces a hormone calledadrenaline that causes you to tense your muscles andincreases your heart rate. When you are relaxed your blood pressure drops slightly. Figures of140/90 mmHg or more indicate you could have aproblem with your blood pressure.

Blood pressure and the kidneysYour blood pressure is not just due to heart action.Several different mechanisms are involved, includingyour kidneys. The water content of the blood isregulated in your kidneys. If you expel a lot of water

18 Catalyst

Water and dissolvedsubstances leavethe blood through thethin capillary walls

If the blood pressure is too high,water cannot re-enter capillaries

Tissue fluid pressurerises relative to blood pressure, and with osmosiswater re-enters blood

Capillary walls are oneflattened cell thick

Low bloodpressure

High bloodpressure

Bloodflow

Tissue

Blood pressurefalls

Osmosis is animportant part of theexchange mechanism incapillary beds.

The amount of fluidthat can flow through apipe is proportional tothe radius4. A pipe cancarry only 1/16th of thevolume of a pipe twiceas wide.

Figure 2 What happens in a capillary bed

Above: A doctormeasuring a patient’sblood pressure

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from blood into urine then the blood volume, andhence pressure, will be lower. When you are short ofwater a chemical is produced in the body calledangiotensin II which causes your arteries to constrict.The pressure of blood inside these narrower arteriesrises. Angiotensin also makes you feel thirsty.

HypertensionSome people have high blood pressure. This is knownas hypertension. Their blood pressure is greater than 140/90 mmHg. There are several causes, but acommon one is fatty deposits in the arteries aroundthe heart. These reduce the internal diameter of theblood vessels so much that less f luid can passthrough. This raises the pressure and puts a strain onthe heart.

If someone’s blood pressure is too high, thepressure will not have dropped enough by the end ofthe capillary bed to allow fluid to return to the blood.Instead it stays in the tissues and makes them swollenand puffy. People with high blood pressure maydevelop swollen ankles and feet.

High blood pressure also damages some of the verytiny capillaries serving important organs such as thekidneys and brain. If blood vessels are damaged, ortheir lining is roughened by fatty deposits, there is agreater risk of a blood clot forming in the blood vessel— a condition know as thrombosis. Blood clots can cause local problems where they form, or theymay be dislodged, to block blood flow elsewhere inthe circulatory system.

Living with high blood pressurePeople with high blood pressure are encouraged tomake some changes to their lifestyle. Taking moreexercise and eating a balanced diet help to reduce the‘furring up’ of their arteries by reducing the amount offats in the blood. Reducing salt intake helps thekidneys regulate the water concentration in blood.Stress and anxiety release adrenaline and nor-adrenalin that raise blood pressure, so managingstress also becomes important.

Some people need treatment to reduce their bloodpressure. Drugs called beta-blockers reduce the rateat which the heart beats and the force of theventricular contractions. As a consequence, bloodpressure is reduced. ACE-inhibitors reduce the effectsof angiotensin and dilate the arteries and veins sothat blood flows more easily.

Jane Taylor teaches biology and is an editor of CATALYST.

19September 2006

Answer to Alchemical wordsearch, page 13The word not in the grid is spirit.

The right ventriclepumping blood to thelungs generates only 25 mmHg (3.3 kpa).

Over 10 million peoplein the UK havehypertension.

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Above: The tiny capillaries that make up the glomerulusin a kidney tubule are a filter for the blood. High bloodpressure or very low blood pressure can lead to kidneyfailure

Artwork of a coronaryartery that has beenpartially blocked by thebuild-up of fatty deposits

L ondon is famous for two particular museumswhen it comes to science — the Science Museumand the Natural History Museum, both in South

Kensington. But a great many other smaller museumsand places of scientific interest are scattered aroundLondon. Here we focus on one group of museums —those associated with various aspects of medicine.

Alexander Fleming Laboratory MuseumThe effect of penicillin on bacteria was first observedby Alexander Fleming, working in a small laboratoryat St Mary’s Hospital in 1928. An in-situ recon-struction of the laboratory, displays and a videouncover the remarkable story of how a chancediscovery became a lifesaving drug destined to revolu-tionise medicine.

The Hunterian Museum at the Royal College of SurgeonsIf you are interested in the science and art of surgery,the Hunterian Museum, housed in the Royal Collegeof Surgeons, is worth a visit. The collections have beenbrought together over four centuries by a cast ofcolourful characters, including the surgeon andanatomist John Hunter (1728–93). There is a fasci-nating mix of human and animal anatomy andpathology specimens, wax teaching models, surgicaland dental instruments as well as paintings, drawingsand sculptures.

Recently reopened after a £3.2 million refur-bishment, there are various permanent displays and achanging programme of temporary exhibitions. Checkthe website for the current programme.

20 Catalyst

Places tovisit Medical museums

in LondonYou can find out moreabout these museumsand many others bylogging on to www.medicalmuseums.org.

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The Alexander Fleming Laboratory Museum is in St Mary’s Hospital, on Praed Street, inPaddington.l Open Monday to Thursday, 10.00–13.00l Closed on public holidaysl Admission: adults £2, students £1Find out more at www.st-marys.nhs.uk/about/fleming_museum.htmV

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The Hunterian Museum at the Royal Collegeof Surgeons is at 35–43 Lincoln’s Inn Fields.l Open Tuesday to Saturday, 10.00–17.00l Closed 23 December to 2 January, GoodFriday and Easter Saturdayl Admission free, donations welcomel Disabled access (see museum website fordetails)Find out more at www.rcseng.ac.uk/museums

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Alexander Fleming’s laboratory

Below: The CrystalGallery at theHunterian Museum

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Old Operating Theatre Museum andHerb GarretThis fascinating museum is located in Southwark, justsouth of London Bridge, and opposite Guy’s Hospital.Hidden in the roof of a church, a 300-year-old herbgarret houses the only surviving nineteenth-centuryoperating theatre, complete with wooden operatingtable and observation stands, from which spectatorswitnessed surgery performed without anaesthesia orantiseptics. The oak-beamed garret was also used forthe storage and curing of medicinal herbs.

British Dental Association MuseumInterested in dentistry? This museum has recentlybeen refurbished and offers modern displaysalongside historic film footage and a CD-ROM OralHistories. The BDAM’s collections include dentalinstruments and equipment, furniture, archives,photographs, fine art and new inventions.

Science MuseumThe Science Museum has a lot related to biomedicinein its main galleries — but high up, on the fourth floor,is a section called ‘Glimpses of Medical History’,where there is a series of historical dioramas. ‘TheScience and Art of Medicine’ and ‘Veterinary History’are on the floor above. To find out more, log on towww.sciencemuseum.org.uk and click on ‘Visiting’ andthen on ‘Gallery guide’.

21September 2006

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Left: Exhibits at theBritish DentalAssociation Museum

Medical museums

M

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C E N T R A L L O N D O N

River Thames

Alexander FlemingLaboratory Museum

British DentalAssociation Museum

Royal College of SurgeonsHunterian Museum

Science MuseumOld OperatingTheatre

and Herb Garret

The Old Operating Threatre Museum is only 2 minutes’ walk from London BridgeUnderground and Mainline Station, at 9a St Thomas’s Street.l Open daily, 10.30–17.00l Closed 15 December to 5 Januaryl Admission chargel Disabled access is limitedFind out more at www.thegarret.org.uk

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The British Dental Association Museum islocated at the British Dental Association’sHeadquarters at 64 Wimpole Street, LondonW1G 8YS.l Open Tuesdays and Thursdays,13.00–16.00; other times by appointmentl Admission freel Disabled accessFind out more at www.bda.org/museum

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The ninteenth-century operating theatre at the OldOperating Theatre Museum

l Try to identify theother medical museumsindicated by the symbol‘M’ on the map.

The human heartHuman heart statisticsYour heart:l is the most active muscle in your bodyl can beat at up to 160 beats per minute when you exercise hardl beats over 100 000 times a dayl pumps up to 6 litres of blood through 20 000 km of blood vesselsl started beating well before you were born

Heart beatThe heart has an in-built rhythm. Theelectrical impulses which travel through theheart muscle, causing it to contract, start atthe natural ‘pacemaker’ in the wall of the leftatrium (1). Initially, the impulses andcontractions spread across the two atria (2).The impulses can only head on to theventricles via a narrow pathway (3) down themiddle of the heart, towards the bottom(confusingly called the apex) (4). Impulsestravel fastest to the apex and slower to therest of the ventricle walls. If you think about it,this pattern makes sense. Blood has to beforced upwards into the aorta or thepulmonary artery. If the natural pacemakingof the heart fails, an artificial pacemaker canbe implanted to overcome the problem.

Healthy heart valvesThe four major heart valves stop blood flowing backwards — back out of theheart, backwards within the heart or back into the heart. Their positions areindicated in the two-dimensional diagram above, in which the heart is drawnto describe its function, rather than to represent its three-dimensionalstructure accurately.

A heart with faulty valves will be unable to pump blood efficiently. As a result,oxygen and carbon dioxide are not moved from and to the lungs as efficientlyas they should be. A person with faulty valves may be short of breath, have ahigher pulse rate and be generally tired. The damaged valve and its surroundingring can be removed and replaced with an artificial valve.

An artificial valve and a pacemaker in placeColoured X-ray of a side-view of a 72-year-old woman’s chest. She has an artificialheart valve (the yellow ring surrounds the valve itself) and a pacemaker (whiteoblong, upper right). You can follow the lead from the pacemaker to its terminationin the heart. It supplies electrical impulses to the heart to keep it beating regularly.You can also see the wire stitches (rings, right) used to pin the bones of the chesttogether, after they were cut to allow open heart surgery

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Point whereimplulsespass ontothe ventriclewalls

Pacemaker located here

Pulmonaryvalve

Aorticvalve

Rightatrium

Thinner-walledright ventricle

Leftatrium

Leftventricle

Atrio-ventricular

valves

Frombody

Tobody

Fromlungs

Tolungs

Zeph

yr/S

PL

Why is theleft ventriclewall thicker?