ocr gateway science b3 revision cards

8/2/2019 OCR Gateway Science B3 Revision Cards

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MoleculesofLifepart2

DNAreplicationandEnzymes

processofreplicationspeededupbyuseofenzymes

enzymesarebiologicalcatalysts

enzymesarenotalive

catalystsspeedupreactionsyetremainunchangedthemselves

Enzymesandrateofreaction

enzymesaresubstratespecific

activesiteiswherereactionoccurs

enzymesworkinoptimumconditionsspecifictoeachtypeofenzyme

enzymescanbedenatured(changedshapeofactivesite)

denaturingofactivesitepreventssubtstratefromfittingperfectlysonoproductmade

denaturingcausedbyincorrectpH

denaturingcausedbytemperaturebeingtoohigh

Lowtemperaturesslowenzymeactivity

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Molecules of life

Cell structure - animal cell

cell membrane - controls movement of substances in and out of cell

cytoplasm - where chemical reactions take place

nucleus - carries genetic information on chromosomes

mitochondion - where respiration takes place inside the cell

Chromosomes, Genes and DNA

chromosomes made up of DNA that form genes

genes carry code for proteins (protein synthesis)

DNA copies itself - DNA replication

Base code sequence (in 3 code sequence e.g. CAA or CGC)

Base codes join up in DNA replicationC - G, and A - T)

DNA base codes form the basis for DNA fingerprinting


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Examplesofdiffusion

Examples

-gasesinandoutofblood-aminoacids,fattyacids,glycerolandglucoseinandoutofblood.

-nitrogenouswasteinandoutofblood.-ureainandoutofblood.-potassiumandsodiumions

betweennervesynapses.-substancestoandfromthefoetusviatheplacenta.-carbondioxide

andoxygeninandoutofleaf

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Diffusion

Diffusion

movement from an area of high concentration to an area of low concentration

diffusion occurs in many areas of the body - lungs, kidneys, small intestine.

diffusion occurs between placenta and mother

semi-permeable membrane

Aiding diffusion

increased surface are

thin layer between cells

moist surface

good blood supply


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DivideandRule-mitosis

Multicellularorganismsgrowlarge

Whengrowingtheorganismscandifferentiatecells

Humancellscontain23pairsofhomologuschromosomes

Mitosis-Fancynameforcelldivision1.Cellresting.2.Chromosomesinthenucleusare

copied.3.Spindleforms,chromosomesarrangedalongequator.4.Chromosomestopolesofcells

(oppositeendsofcell).5.Celldivides-twogeneticalyidenticaldiploiddaughtercellsformed.

Thistypeofcelldivisionoccursingrowthandrepair.

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Keeping it moving

Circulatory system

Made up of - arteries, veins, capillaries, heart and blood.

Arteries - thick elastic and muscular wall to withstand high pressure.

Veins - large lumen (space) to help blood flow (low pressure) and valves to stop back flow.

Capillaries - thin permeable wall allows exchange of materials.

Heart - double pump.

Heart and Blood

Atria and ventricles (ABOVE).

Valves in the heart stop the blood flowing backwards.

Pulmonary artery takes to lungs, aorta to body, vena cava back from body, left side thicker

wall.

Blood - red blood cells (carry oxygen), white blood cells (fight disease), plasma (dissolved

food, waste and carbon dioxide), platelets (broken down cells help clotting)


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Growingup

Plantcells-sameasanimalcellswiththeadditionof;

chloroplasts-containchlorophyllforphotosynthesis

vacuole-usedforstorageofsapandsupportofcell

cellwall-madeofcellulosethisstrengthensthecell

Growth

animalgrowbyincreasingincellnumber

differentiationofcellsoccursearlyinanimaldevelopment

plantcellsmaintainabilitytodifferentiate

plantcellsgrowbyelongation

mitosisoccursatroottipsandshoots.

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Divide and rule - meiosis

Meiosis - Fancy name for sex cell division.

Haploid cells formed (gametes - sperm and ova.) 1. Homologous chromosomes pair up. 2. One

from each pair goes to poles. 3. Strands of chromosomes move to opposite poles. 4. Four new

haploid cells formed (half thenumber of chromosomes of normal cells).

Gametes

Sperm cells - tail to swim, streamlined, mitochondria to power tail, acrosome on head to help

pentrate ovum membrane.

Ovum - larger than sperm, large 'food' store

Variation occurs in sexual reproduction as genes shuffled in meiosis


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Growingup-gestation

Gestation=pregnancy

Humangestation=266days(9months)onaverage

Foetusgrowsquicklyfromembryointheuterus.

Differentbodypartsgrowatdifferentrates.

Headgrowsquickly.

Humangrowth

infancy-fastest%growthrate

childhood

adolescence

maturity

oldage

Babygrowthmeasuredusingmassandheadsize.Shownongraphsinexams

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Growing up - stem cells

Stem cells

undifferentiated animal cells.

found in embryos.

can be found in adult bone marrow but only able to differentiate to a limited number of cells.

Stem cell research

investigating cancer.

drug testing.

transplants - grow new organs

Ethical issues involved because of the nature of stem cell origin.

right to life?

wasted embryos?


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NewGenesforOld

Characteristics-desiredattributeofplantoranimalYield-quantityneededincreasedSelective

breeding-producesplantoranimalwithdesiredcharacteristicsCrossbreeding-selectionocharacteristicsfromtwobreedsIn-breeding-limitedgenepoolmorechanceofdiseaseand

problemsMutation-corruptionofDNAsequencethataltersorchangesprotinproduction

Selectivebreeding

Adesiredcharacteristicisidentified.Plants/animalsshowingcharacteristicbreduntiloffspring

showdesiredcharacteristic.Takesmanygenerations

modernplants-tomatoplantbredtogetsize,taste,colour,orshape

cattle-bredorquantityofmilk,qualityofmilkorbeefproduction.

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Controlling plant growth

Plant hormones (auxins) control plant growth

auxins used in roots, shoots, flowering and fruit

auxins respond to different stimuli

phototropisms - light

geotropisms - gravity

roots are negative phototropisms and positive geotropisms.

Commercial use of hormones

Rooting hormones - encourages growth of roots. Used in cuttings.

Fruit ripening hormones - cause fruit to ripen during transport

Weedkillers - disrupt growth pattern of target plants

Control dormancy - speed up or slow down growth and development


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MoreoftheSame

Clones-geneticallyidenticalCloning-involvesasexualreproduction(mitosis)

Cloninganimals

Animalartificiallyinseminated

Fertilisedeggdividesto8cellembryo

8cellembryosplitinto4embryosof2cells

2cellembryosinsertedintosurrogateanimals

2ndmethodinvolvesremovaloffertlisedeggcellnucleusandreplacementwithdonornucleus

(Dollythesheep)

Plantscanbeclonedbytakingacuttingandusingrootinghormones

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New genes for old - part 2

Genetic engineering - Method

Characteristic selected

Gene for characteristic isolated

Gene inserted into chromosome of different organism

Organism replicated to produce many copies

Enzyme used to 'cut' gene from chromosome

Reasons

improved resistance to herbicides and disease

improve quality of food

to produce substance required

Example - insulin producing bacteria

Ethical Considerations - possible cross breeding, mutation from genetc modification


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MoreoftheSame

Asexualreproductioninplants

Potato-tubergrowsshootsandrootsformcloneofparentplant

Strawberries-runnersfromparentplantgoalonggroundtofromcloneofparentplant

Spiderplants-plantletsgrowfromparentplant

Cuttings-donebygardenersuserootinghormones

Advantagesofcloning

lotsofsameorganismproduced

speed

abilitytogrowfromorganismswithpoorbreeding

Disadvantages

geneticallyidenticalreducedgenepool

reducedvariation

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