Biology Revision Guide

7/29/2019 Biology Revision Guide

1/5

Cardiovascular disease (CVD)

12

Unit 1: Lifestyle, Transport, Genes and Health1

Green Book 1.1,1.2 Orange Book 1.1

Bloodclottingisavitaldeencemechanismorthebody.Iyousueracutorgraze,thenclottingcan: minimisebloodloss helppreventtheentryopathogens providearameworkorrepair.But,iaclotoccursinsideabloodvesselitcanbeverydangerous,blockingbloodflowandsometimesleadingtothedeathotissues.

Clotormationisstimulatedwhenthereisdamagetoabloodvessel.Damage

exposescollagenfbrestowhich platelets(smallcellswithnonucleusormedwhenaprecursorcellragments)attach.Theplateletsreleaseaclottingactorcalledthromboplastin.InthepresenceocalciumionsandvitaminK,thromboplastinconvertsinactiveprothrombinintoactivethrombin.Thisinturnconvertsthesolublefbrinogenintoinsolublefbrin,whichormsanetworkofbres,trappingcellsanddebristomakeaclot.

Atherosclerosis

13

Topic 1: Lifestyle, health and risk 1

Green Book 1.1, 1.2 Orange Book 1.1

Treatment of CVD

RiskoCVDcanbereducedbyliestylechanges: stoppingsmoking moderateexerciseseveraltimesaweek stoppingover-consumptionoalcohol dietarychanges,especiallyloweringcholesterolandsaturatedatintake.

Medicaltreatmentswhichcanhelpare: reducinghighbloodpressure(usuallydefnedasover160(systolic)/100(diastolic))

byantihypertensives reductionobloodcholesterol,e.g.bydietorbydrugssuchasstatins

anticoagulants platelet inhibitors.

ThetablesummarisessomedrugsusedortreatingCVDandtherisksassociatedwiththeiruse.

Make sure you know that the

two substances, prothrombin

and fibrinogen, are the inactiveforms. Promeans, roughly, first as

in prototype. You may have met

trypsinogen at GCSE and know that

the ogensuffix means the

inactive form.

The formation of an atherosclerotic plaque is a positive feedback phenomenon.

Athero (artery) sclerosis (hardening)

the plaque makes the wall become

less elastic and narrows the a rtery.

CVD

stroke blood supplyto part ofthe brainis cut off

angina narrowing

of coronaryblood

vesselsheart attack blockage ofcoronaryvessels

peripheral vascular disease thrombosis, narrowing of arteries toperiphery, especially common in the legs

The various types of cardiovascular disease (CVD), all caused as a result of atherosclerosis.

Drug treatment Mode of action Risks/side effects

diuretics

(antihypertensive)

increasevolumeourine;

lowersbloodvolumeand

pressure

veryoccasionaldizziness,nausea,

musclecramps

betablockers

(antihypertensive)

blockresponseoheart

tohormonesandmake

contractionslessrequentand

lesspowerul

possiblelinkwithdiabetes

ACEinhibitors

(antihypertensive)

blocktheproductiono

angiotensin(ACEstands

orangiotensinconverting

enzyme)whichnormallycausesarterialconstrictionand

ariseinbloodpressure

cough,dizziness,heartarrhythmia,

impairedkidneyunction

s tatins lower cholest er ol level inthe

bloodbyblockingtheliver

enzymethatmakescholesterol

muscleaches,nausea,constipation

anddiarrhoea;veryrarely

inflammationreactionscanoccur

which,evenmorerarely,areatal;

also,againrarely,liverailure;also,

peoplemaystoptryingtoeata

healthydiet,leavingitalltothe

statins

anticoagulants,e.g.

wararin

reduceriskoclotormation riskouncontrolledbleeding;dosage

controlisessential

plateletinhibitory

drugs,e.g.aspirin,

clopidogrel

makeplateletslesssticky aspirinirritatesthestomachlining

andcancauseseriousstomach

bleeding;usingclopidogrelwith

aspirincanmaketheriskevengreater

You probably will not know enough

about what these treatments do to

work out what the risks might be,

so try to learn them thoroughly.

Q1 Listthefactorswhichmustbepresentinorderorabloodclottoorm.Q2 EveniallthebloodclottingchemicalsyouhavelistedinQ1werepresent,

thiswouldnotallowaclottoorm.Whatelseisneeded,apartromarangeochemicals?

Q1 Use the outline flowchart

below to summarise the

clotting process by substituting

the correct terms from the

description on page 12.

Thinking TaskTheriskosueringromCVDisincreasedby:

geneticactors

age

gender

highbloodpressure

liestyleactorsdiet,exerciseandsmoking.

(Seepage16ormoredetails.)

increasedriskobloodclottingintheartery

inflammatoryresponse

whitebloodcellsmoveinto

thearterywall

cholesterolbuildsup,leadingtoormation

oatheroma

build-upocalciumsaltsandfbresleadingtoplaque formation

narrowingoartery

raisedbloodpressure

damage toendothelial liningo

artery(e.g.bysmoking,highbloodpressure)

A

B

C D

E F

clot

G H


2/5


3/5

Cells and organelles

52

Unit 2: Development, Plants and the Environment2

Green Book 3.1 Orange Book 3.1

Somesingle-celledorganismsandallmulticellularorganismssuchashumansaremadeupoeukaryoticcells.Aeukaryoticcellalwayscontains:

anucleus,containinggeneticmaterial,surroundedbyadouble membrane(orenvelope

organelles(structures)inthecytoplasm,eachsurroundedbyoneortwomembranes.

Animal cell ultrastructureUltrastructureisthenameorthefnestructurethatisrevealedwhenusingapowerulmicroscopesuchasanelectronmicroscope.Theultrastructureoaeukaryoticanimalcellanddetailsosomeoitsorganellesareshownbelow.

Cross-section of a generalised animal cell a typical eukaryotic cell.

Protein transport within eukaryotic cells1. Amino acids made intoprotein on the ribosomes.

2. Newly made proteinstored in rER cavity. 5. Protein being modified

in the Golgi apparatus.

vesicle which may containextracellular enzymes

3. Protein being packaged atthe ends of rER. Membranecloses forming a vesicle.

4. Vesicles, pinched off therER, transport proteintowards the Golgi apparatus.

The Golgi apparatus and rER are involved in the making and movement of proteins through the cell. The

arrows show the direction of transport. The proteins leave the cell by exocytosis, when the vesicles fuse with

the cell surface membrane.

53

Topic 3: The voice of the genome 2

Green Book 3.1 Orange Book 3.1

Make sure that you can recognise

and label the organelles from

electron microscope (EM) images

as well as from diagrams.

ThemodifedproteinisplacedintovesiclesbytheGolgiapparatus.Somemaybeexportedoutothecell,suchasextracellularenzymes,e.g.amylaseandprotease.

Golgi apparatusZl^kb^lh_lbgè^%\nko^]lZ\l^g\ehl^][rZf^f[kZg^^Z\alZ\bllfZee^kmaZgmaîkôbhnlhg^fZgro^lb\e^l\enlm^kZkhng]ma^@he`bZiiZkZmnl

rER (rough endoplasmic reticulum)Zl^kb^lh_lbgè^%_eZmm^g^]lZ\l^g\ehl^][rZf^f[kZg^ribosomeshgma^lnk_Z\^

sER (smooth endoplasmicreticulum)Zl^kb^lh_lbgè^%mn[neZklZ\lfZ]^h_f^f[kZg^

nucleuslnkkhng]^][rZ]hn[e^f^f[kZg^!^goêhi^"ihk^l!ahe^l"bgma^gn\e^Zk^goêhi^]Zkd&lmZbgbg`Zk^Z%\Zee^]ma^nucleolus%pbmabgma^gn\e^Zk^goêhi^

centriolesmphaheehp\rebg]^klZkkZg`^]Zmkbàm&Zgè^lmh^Z\ahma^k

lysosome^g\ehl^][rZlbgè^f^f[kZg^\hgmZbgbg`]b`^lmbo^^gsrf^l

mitochondrialnkkhng]^][rZ]hn[e^f^f[kZg^!^goêhi^"bgg^kf^f[kZg^_he]^]bgmh_bg`^k&ebd^

ikhc^\mbhgl\Zee^]\kblmZ^!lbg`neZk%\kblmZ"\^gmkZeZk^Z\hgmZbglZcêer\Zee^]ma^fZmkbq_ehZmbg`bgma^fZmkbqZk^3ribosomes=G:!ZlZehhi"

A

B

Onewaytoinvestigateproteintrafckingistouseradioactiveaminoacids.

Atissuewassoakedinasolutionoradioactiveaminoacidsorashortperiodotimeandthentranserredtoasolutionwithnon-radioactiveaminoacids.

Thetablebelowshowstheamountoradioactivity,asapercentageothe

totalradioactivityinthecellsothistissue,oundinthreeorganelles,atthreedierenttimesaterbeingtranserredtothenon-radioactivesolution.

Organelle Percentageoftotalradioactivityincellsafter

tissuetransferredtonon-radioactivesolution

5min 10min 45min

vesicles 0 5 60

rER 80 10 5

Golgiapparatus 10 80 30

totalradioactivity 90 95 95

(a) ThevesiclescontainingradioactivitycaneithercomeromrERortheGolgiapparatus.Usingevidenceromthetable,suggestwhetherthesevesiclescomeromrERortheGolgiapparatus.

AsmostotheradioactivityisintherERat5minutes,youwouldexpectalotinthevesiclessoonaterwardsitherERmadethesevesicles.At10minutes,therewasonlyalittleinthevesiclesandalotintheGolgiapparatus.ThissuggeststhattheGolgiisjustbeginningtomakethesevesicles.Thisisconfrmedat45minuteswhenthereislessradioactivityintheGolgiapparatusasitisnowinthevesicles.Thevesicles,thereore,comeromtheGolgiapparatus.

(b) Suggestanexplanationorthedierenceinthetotalradioactivitybetween5minutesand10minutes.

Atfrst,itlooksasthoughradioactiveaminoacidshavesuddenlyappearedbutthiscannotbe.Thisisaquestionaboutexperimentaltechnique.Datawascollectedatthreetimeintervalsratherthancontinuously.Itcouldbethatat4minsmoreradioactivitywasattherERbutby5minsithasalreadybeenpackagedandisintransittotheGolgi.By10minsithasarrivedattheGolgi.


4/5

2 Unit 2: Development, Plants and the Environment

Multicellularorganismsareorganismsmadeupomanycells.Thesecellsarenotrandomthroughoutthebodybutareorganised.Thereare fourlevelsoorganisationasshownbelow.Plantandanimalexamplesaregiven.

Q1 Explainwhatismeantbythetermsystem.

Q2 Suggestonereasonwhyorgansareconsideredmorecomplexthancells.

Q1 Make a table to compare a

tissue and an organ.

Thinking Task

54 55Green Book 3.1 Orange Book 3.3

Q1 During cell division, an animal

cell does not have a nucleus

but is still considered to be

eukaryotic. Suggest tworeasons

why this cell is still considered to

be eukaryotic.

Q2 Draw a diagram of a Golgi

apparatus.

Q3Make a flowchart to describeprotein trafficking from when

the protein is first formed until

it is released from the cell as an

extracellular enzyme.

Thinking Task

Q1 Givethreestructuraldierencesbetweenatypicalprokaryoticcellandahumanlivercell.

Q2 Giveonesimilaritybetweenthestructureoanucleusandamitochondrion.

Q3 DescribehowyoucoulddistinguishrERromGolgiapparatus.

Q4 Listfourmembrane-boundorganellesoundinananimalcell.

Feature Prokaryoticcell Eukaryotic

Animalcell Plantcell

nucleuswithenvelope absent present present

membrane-boundorganelles absent present present

DNAoundas aloop separatestrands separatestrands

slimecapsule sometimespresent neverpresent neverpresent

flagella simple(ipresent) complex(ipresent) absent

cellwall present(bacterial) absent present(cellulose)

relativesizeocell small medium large

Table to compare a prokaryotic cell with two typical eukaryotic cells.

Allcellsomulticellularorganismsareeukaryotic.Palisadecelland

livercellareexamples.

Tissuesconsistooneoraewdierenttypesocellthatwork

togethertoperormaunction.Epidermaltissueandmuscletissue

areexamples.Organsaremadeupovarioustissuesgroupedtoworktogether

andperormtheirunctionefciently.Leaandheartareexamples.

Systemscomprisevariousorgansthatworktogethertoperorma

large-scaleunction.Manypeoplebelievetherearenosystemsin

plants.Thedigestivesysteminhumansisanexample.

cells

tissues

organs

systems

Thediagramshowsasectionthroughalea.Explainwhythisleaisconsideredtobeanorgan.

Thequestionasksaboutthisleaf,sowemustreertothediagram.Notethatthereisnoreerencetochloroplastssonomarkswouldbegivenorwriting

aboutunction.

Statethatanorganismadeuposeveraltissues.Pointoutthatthediagramshowspalisadetissueandalsoepidermalandspongytissue.Sothisleahasthreetissuesvisible,henceisanorgan.

epidermal cell

one cell from thepalisade tissue

spongy cell

guard cell

Section through a leaf.

Magnification and estimating sizeImagineacellthatmeasures10mmacrossonapagebecauseithasbeenmagnifed1000times.Fromthiswecanworkoutthetruesizeothecellbyusingtheormulabelowandtheexample.

Calculationstages

1 Usingthepyramid,youcanseethattruesizeisoundbydividingimagesizebymagnifcation.

2 10103m(10mm)1000=

3 Theanswercomesouttobe10106mor10m

NB:Toworkoutmagnifcationusingthepyramid,useimagesizetruesize.

When asked to compare, you should

include similarities and differences.

Cellular organisation

Topic 3: The voice of the genome 2

flagellum*

photosyntheticmembranes*

loop of DNA (nucleoid)

glycogen granules,lipid droplets

cell surface membrane

smallribosomes

cell wall

plasmids*

* = not present in all bacteria

A typical prokaryotic cell. Compare this to the diagram of the eukaryotic cell.

Differences between a prokaryotic cell and

a eukaryotic cell

Make sure you realise that bacteria

are prokaryotes and that both plant

and animal cells are eukaryotic

cells.

54 Green Book 3.1 Orange Book 3.1

Make sure all dimensions are in

the same units before you start

the calculation. This is a commonsource of error.imagesize

truesize

magnifi-cation


5/5

Species and biodiversity

70

Unit 2: Development, Plants and the Environment2

Green Book 4.3, 4.4 Orange Book 4.1, 4.3

Biodiversityisthevarietyodierentorganismswithinahabitat.Twoaspectstoconsiderare: Speciesrichnessthenumberodierentspecieswithinanareaoknownsizeata

particulartime.Aspeciesisagroupoorganismswithsomanyeaturesincommonthattheycanmateandproducesexuallyviableospring.

Geneticdiversitythegeneticvariationwithinaspecies.

How to measure these two aspects of

biodiversity1 Measuringspeciesrichness

Toestimatethespeciesdiversity,randomsamplingcanbecarriedout.Anumberoquadrats(oten10)oknownsizearerandomlyplacedinanarea.Allthespeciesoundineachquadratarerecordedandusedtoestimatethetotalspeciesrichness.

71

Topic 4: Biodiversity and natural resources 2

Green Book 4.3, 4.4 Orange Book 4.1, 4.3

Q1 Makeaflowcharttoexplainhowspeciesrichnesscanbemeasured.Q1 In a large population of

organisms, eight different

alleles were found for one gene.

However, when only half of the

population was sampled, six

different alleles were found

for the same gene. Suggest

twopossible reasons for the

absence of the two alleles.

Thinking Task

Make sure you know the difference

between diversityand densityof

organisms.

1 Usingthedatainthetable:

aworkoutthenumberospeciesoundinthe3m2

sampled.

b constructabarcharttocomparetherequencyooccurrenceoeachspecies.

Answers a Itdoesntmatterwhetherthe

speciesoccursonlyonceormanytimesasthisquestionitemisaskingorpresenceorabsenceonly.Theansweris,thereore,5asAtoEoccuratleastonce.

b Frequencyisthetotalnumberotimeseachspeciesisound.ForspeciesAitis1andorspeciesDitis3.Thebarchartisshownbelow.

1m2quadratnumber

Species 1 2 3

A

B

C

D

E

F

Frequ

ency

ofoccurrence

3

2

1

A B

Species

EC D F

0

2 Measuringgeneticdiversity

Findthenumberodierentallelesinagenepool.

Eachgenemayhaveonetomanydierentalleles.

Thetotalnumberogenesaspecieshas

Make sure you know the difference

between allelesand genes. A

gene codes for a characteristic,

e.g. eye colour. The alleles are

the alternative forms, e.g. blue or

brown, of a gene that codes for a

variable characteristic, e.g. eye

colour.

EndemismEndemismdescribesthesituationwhereaspeciesisoundinonlyoneparticulararea.Thering-tailedlemurisrestrictedtotheislandoMadagascarandsoisconsideredtobeendemictoMadagascar.

A new taxonomic groupingThreedomainshavebeenidentifedbasedonmolecularphylogeny.Molecularphylogenycomparesthestructureoaparticularmoleculeromdierentorganismstodiscovertheirdegreeoevolutionaryrelatedness.Themoresimilarthestructureothemolecule,themorecloselyrelatedtheorganismsaretoeachother.Thisisbecausechangesinmoleculestructuregenerallyoccuronlyslowlyastheyarecaused

bymutations.

Thethreedomainsare:

Bacteria

Archaea

Eukaryota.

Theideaothethreedomainsillustratesthescientifcprocessandtheimportantroleocriticalevaluationonewdatabythescientifccommunity.

Mutations in DNA and the

structure of the proteins produced

are covered in Unit 1.

Alllieissplitintotheprokaryotesandeukaryotes

AscientistcalledWoesesuggested

athirdgroupwhichhecalledtheArchaea;hesupportedhissuggestion

withevidence

Otherscientistsstudytheevidencecareully;thisiscalledpeer review

Otherscientistsstarttocollectevidence

Mostscientistsacceptedthatallliewaseitherprokaryotic(cellswithoutatruenucleus)oreukaryotic(cellswithatruenucleus).

Woesepublishedapaperinascientifcjournalusingmolecular

phylogenicevidence.Thisisonewayoinormingthescientifccommunityoadiscovery.Otherwaysincludepresentinginormation

ataconerenceorusingtheInternet.

Thescientistsarecheckingthattheevidenceisaccurateandcorrect,thattheconclusionsdrawnaresensibleandthatthemethodsused

areappropriate.

Theevidencewillhelptosupportthesuggestion,torejectthesuggestionorleadtoamodifcationothesuggestion.Thereisstill

debateaboutWoesessuggestionbutmuchothescientifccommunitynowacceptthethreedomains.

Documents

Biology Revision Guide