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Organelle Structure and function
Nucleus • enclosed in double membrane with pores
• contains chromosomes with genes made of DNA to control protein
synthesis
Ribosomes • made of RNA and protein
• free in cytoplasm or attached to RER
• site of protein synthesis
Rough endoplasmicreticulum
•
interconnected sacs with ribosomes attached• transport proteins to other parts of cell
Smooth endoplasmic
reticulum
• synthesis of lipids and steroids
Mitochondria • double membrane – inner folded into cristae
• site of later stages of aerobic respiration
Centrioles • one pair found in animal cells
• made of protein microtubules
• involved in spindle formation and cellular transport
ysosomes • digestive en!ymes wrapped in membrane
• brea"down of unwanted structures or old cells
Nucleolus • dense body in nucleus
• synthesis of ribosomes
#esicle • Small fluid$filled sac in the cytoplasm% surrounded by membrane
• &ransports substances in out of the cell via the cell membrane and
between the organelles
• Some are formed by the 'olgi apparatus (e)ocytosis* and some
by the plasma membrane (endocytosis*
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CellsEukaryotes (such as human liver
cell)
Prokaryotes (such as a bacterium)
Larger cells (2-200 um diameter) Very small cells (
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Cell cycle:
i n t e r p h a s e
G1 (first gap phase) synthesis of cellular proteins and organelles
S (synthesis phase) replication of DNA
G2 (second gap phase) synthesis of spindle proteins
d i v i s i o n
mitosis (nuclear
division)
separation of the 2 DNA helices making up the
chromosome
cytoplasmic division cleavage of a single cell into two daughter cells
Mitosis phases:
Prophase:• idea that during prophase +chromosomes , chromatids- (becoming* visible .
• idea of centrioles move to opposite poles .
• reference to formation of +spindle ,spindle$fibres , microtubules- .
• disappearance of nucleolus , nucleoli .
brea"ing down of nuclear +envelope , membrane- (in prophase* .
Metaphase:
• nuclear envelope is bro"en down by metaphase , e/ .
• (at metaphase* +chromosomes , centromeres- attached to spindle (fibres* .
• idea of +chromosomes , chromatids- lined up at e/uator .
Anaphase:
• centromeres divide , split , separate , pulled apart.
• +spindle fibres , microtubules- become +shorter , contract , condense-.
• chromatids +separate , pulled apart-.
• chromosomes , chromatids move towards (opposite* +poles , ends , sides ,
centrioles-.
Telophase:
• +spindle fibres , microtubules- have now +vanished , bro"en down , e/-.
• chromosomes +unravel , uncoil , e/- (and become invisible* .
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• reference to reformation of +nuclear membrane , envelope , e/- , +nucleolus ,
nucleoli-.
Diagrammatic representation of mitosis
Order: A D C ! " note that A #interphase$ is sometimes referred to as part of mitosis %utmost of the time it&s listed as separate.
Difference et!een mitosis and meiosis
Meiosis Mitosis
(3omologous* chromosomes associate inpairs
(3omologues* independent,do not pair(4'N2RE ref1 separation
Crossing$over,chiasmata formation No crossing$over
&wo,(nuclear stages* divisions, 5 6 offspringcells
2ne,(nuclear stage* division, 5 7 offspringcells.
'enetically different (product* 'enetically identical (product*.
Cyto"inesis
&he cytoplasmic division of a cell at the end of mitosis% bringing about the separation
into two daughter cells1
#unction$importance of spindle
• Attachment of centromeres.
• Separation of (daughter* chromatids.
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Plants
%ylem tissue structure Centre of the stem'
• long cells , tubes with no end walls.
• continuous water columns.
• no cytoplasm , no organelles,named organelle.
• to impede,obstruct flow , allows easier water flow.
• thic"ening,lignin.
• support , withstand tension , waterproof , "eeps water in cells.
• pits in walls.
allow lateral movement , get round bloc"ed vessels.
Sclerenchyma fires structure Outer edge particularly'
• 8undles of dead cells running vertically.
• 3ollow lumen.
• No end walls.
• &hic"ening,lignin.
• support , withstand tension.
• More cellulose than other plant cells.
Structure of function of starch
• Contains amylose and amylopectin.
• Amylose not a mar"' :
• ong and unbranched chains.
• 9$6 glycosidic bonds.
• coiled structure.
• (so* compact.
•
(so* can fit more in a small space.
Amylopectin not a mar"' :
• (long*% branched chains.
• (has* 9$6 and 9$: glycosidic bonds.
• side branches which can be bro"en down /uic"ly.
• 4nsoluble.
• so water doesn;t cause it swell via osmosis
Structure of cellulose
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• (cellulose* contains beta glucose , e/ .
• (glucose molecules*
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Organelle Diagram Description Function
Cell !all• Rigid structure
surrounding
plant cells.• Cellulose.
• Supports plant cells
Middle lamella • 2utermost
layer.
• Adhesive.
• Stability
Plasmodesmata • Channels in cell
wall that lin"ad
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Amyloplast • Small organelle
enclosed bymembrane.
• Starch
granules.
• Storage of starch.
• Converts starch bac" t
glucose.
(acuole & Tonoplast • #acuole is a
compartmentsurrounded bya membranecalled thetonoplast
• #acuole contains cell
(water% en!ymes%
minerals% waste produ
• &urgidity to prevent
wilting
• 8rea"down and isolati
of unwanted chemical
• &onoplast controls wh
enters and leaves the
Cell !all structure
• Ref to cellulose .
• Cellulose arranged into microfibrils .
• Embedded into a matri) .
• Named component of matri) e1g1 pectin , hemicellulose .
• Ref to +primary and secondary cell walls , several layers of microfibrils- .
• Ref to plasmodesmata .
Plant fires• cellulose microfibrils (in cell wall* .
• reference to net$li"e arrangement (of microfibrils* .
• secondary cell wall .
• reference to secondary cell wall being thic"er .
• idea that these features ma"e them the plant fibres strong .
Sustainaility
• #O3 A 4A05 ) Oil)%ased plastics and fuels are not sustaina%le as$:
• Release carbon dio)ide , ref1 to global warming , pollution .
• plastic is from oil .
• oil is a non$renewable resource .
• 'eneration of non$biodegradable waste .
• (however* +plants , starch- are renewable .
• plants can be re$grown , e/ .
• (fibres often biodegradable so* doesn;t accumulate , doesn;t ta"e up landfill space ,
e/ .
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Disad)antages
• &he ropes made from plant fibres aren;t as strong.
• 8ags made out of paper are less strong than plastic bags and disintegrate when wet.
• Degradation of waste re/uires aerobic organisms% so little happens in deep landfill
sites.
• Closer to the surface% methane (a greenhouse gas* is often produced.
Tissues of a leaf
• ower epidermis – contains stomata to let air in and out for gas e)change
• Spongy mesophyll – full of spaces to let gases circulate
•
=alisade mesophyll – most photosynthesis occurs here• >ylem – carries water to the leaf ? transports mineral ions
• =hloem – carries sugars away from the leaf
• @pper epidermis – covered in a waterproof wa)y cuticle
Plants re*uirements of !ater + mineral ions
• ater.
• =hotosynthesis.
• Structural rigidity , transport minerals , temperature regulation.
• Magnesium ions.
• Chlorophyll.• Nitrate ions.
• DNA , protein , chlorophyll production.
• Re/uired for plant growth , fruit production , seed production.
• Calcium ions.
• =lant growth.
Digitalis
• Bo)glove e)tract.
• &reated dropsy.
• reference to digitalis as active drug.• idea of e)tracting drug (from the plant , soup* , tested on patients ,
Starch Plant fibres
• ound in all plants
• !ioplastics " less fossil fuel used up
# crops can $e regrown%
• &ehicle fuel " such as $ioethanol%
Same reasoning as a$ove%
• 'ther uses include glues plaster
hair mousses and antiperspirants%
• opes and fa$rics " less fossil fuel
used up # crops can $e regrown tomaintain supply
• *roducts are $iodegrada$le " this
means less accumulates and fills uplandfills%
• +asier to grow and process "
cheaper and easier for developingcountries
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• idea of try to find suitable dose , trial and error .
Modern day drug testing
• idea that only contemporary testing will use animals , e/ .
• idea that only contemporary testing will +test on healthy people , have phase 9- .
• idea that +phase 9 , e/- is to +detect side effects , find safe dosage- .
• idea that only contemporary testing will pay volunteers .
• idea that only contemporary testing may involve double$blind trials .
• idea that after phase 9% phase 7 occurs – drugs are tested on a larger group of
people .
• idea that this chec"s how effective the drug actually is .
• idea that only contemporary testing will +use statistical analysis , reference to phase 0
, use large number , comparison to e)isting treatments - .
• idea of more regulation .
• idea of controlling +factors ,variables , e/- in tested cohort e1g1 age% lifestyle .
Placeo
• idea of two groups .
• idea that group 9 is given +placebo , inactive substance , sugar pill , e/- .
• reference to placebo effect .
• idea that other group is given the drug .
• idea that this chec"s the effectiveness of the drug , e/ .
Doule,lind trial
• idea that neither doctors nor patients "now placebo,drug group.
• idea that this reduces bias.
• reference to phase 7 , 0.
-eaf cross,section
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#6hloem 7 ,'lem in 8ascular %undle$
Stem cross,section
P =hloem. . Sclerenchyma fibres. R >ylem. S Corte). T Epidermis. / Cambium
Adaptations in different' %erophytes relating to !ater
• shallow roots enable rapid upta"e of rainfall.
• widespread,shallow roots allow collection of larger volume water,over a larger
area,rapid upta"e of water.
• swollen stem for water storage.
deep roots for accessing deep groundwater.
small, no leaves so little transpiration.
Structure of lea)es of %erophytes to "eep !ater in
• Reduce number of stomata. reduce surface area
• &hic" wa)y cuticle. increases diffusion distance
• eaves reduced to spines. reduces surface area
• Epidermal hairs. reduced diffusion gradient
• Sun"en stomata. reduced concentration difference
• Curled leaves. reduced concentration gradient
0n)ironmental factors the influence !ater loss in a leaf
• temperature .
• increase gives more ("inetic* energy , movement to water molecules .
• on surface of spongy mesophyll cells .
• greater evaporation (into air spaces* .
• increases diffusion gradient , rate (of water vapour through stomata* .
• wind , air movement .
• increases , speeds removal of water vapour , humid air .
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• from (leaf* surface, stomata .
• increases diffusion gradient (of water vapour through stomata* .
• decreases boundary layer .
• humidity .
• increase means more water vapour around leaf , stomata .• reduces diffusion gradient (of water vapour through stomata* .
• light intensity .
• increase causes stomata to open , widen .
• so more diffusion of water vapour .
• from air spaces (in spongy mesophyll* .
• water stress , e)tremely high temperature , high winds .
• stomata close .
• less diffusion .
1o! to find surface area of a leaf
• draw round leaf on graph , s/uared paper , grid .
• count s/uares
02planation of !ater path!ays as it tra)els from the epidermis of a root to a %ylem)essel3
• apoplast pathway described .
• e1g1 water moves through the cell walls;
•or water moves through the spaces between cells;
• symplast pathway described .
• e1g1 water moves through the cytoplasm;
• reference to the vacuolar pathway.
• e1g1 water moves through the vacuoles;
• reference to the endodermis and +Casparian strip , layer of suberin , wa)y layer- .
• function of the Casparian strip .
• e1g the Casparian strip is waterproof; or stops movement of water in the apoplast
pathway
Role of the epidermis
• endodermal cells have Casparian strip .
• reference to +suberin , e/- .
• which is waterproof , e/ .
• stops movement of water in apoplast pathway , description .
• water directed into symplast pathway , description .
• reference to +control of upta"e , active transport of ions (into )ylem*- .
1o! AT of mineral ions into 2ylem )essels in the roots results in !ater entering)essels and then eing mo)ed up the 2ylem tissue
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• ater potential in )ylem reduced (by entry of ions*.
• ater potential gradient established between )ylem and surrounding cells.
• =lasma membranes of surrounding cells are partially permeable.
• ater enters )ylem by osmosis.
• #olume of water in )ylem increases.• Cannot move bac" due to gradient.
=ressure in )ylem increases (and forces water upwards*.
Cohesion,tension theory
• Evaporation from leaves , transpiration.
• ater in )ylem under tension,negative pressure,pulled up.
• ater molecules cohere,stic" together,form hydrogen bonds. F1gnore: references to
adhesionG
So water a single column.
Another mar" scheme for cohesion,tension theory• water evaporates,transpires.
• reduces water potential , creates water potential gradient , increases
osmotic gradient .
• moves via apoplast pathway.
• water drawn out of )ylem.
• creates tension,pulling effect , creates negative pressure (in conte)t*.
• cohesive forces or 3 bonding between water molecules , water moves as a column
/ses of !ater in a plant
• photosynthesis .
• +component , e/- of +cytoplasm , sap- .
• water as a solvent ,e/ .
• water as a transport medium ,e/ .
• involved in thermoregulation , e/ .
• reference to role in structural support .
• reference to involvement in hydrolysis .
• reference to turgor changes .
Transpiration
• oss of water vapour from the surface of the plant% mainly from the leaves .
Root pressure in relation to !ater mo)ing through the 2ylem
• 4nvolves active transport.
• Secretion , movement of salts into )ylem.
• Reference to role of endodermis .
• ater moves along water potential gradient .
4hy less !ater is lost at upper surface of lea)es
• more stomata on the lower surface.
• (thic"er* wa)y cuticle on the upper surface .
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Molecular phylogeny
• Study of evolutionary history of organism groups
• Measures relation between species.
• DNA and proteins e)amined – the more closely related the more similar the
molecules
Domains
• 8acteria% Achaea and Eu"arya .
• =ro"aryotae in Archaea and 8acteria .
• 2ther "ingdoms (organisms with a nucleus* in Eu"arya .
• Archaea and bacteria distantly related% so classified into two domains .
567GDOM 0%AMP-0S #0AT/R0S
Pro"aryotae 8acteria• =ro"aryotes
• Single$celled
• No nucleus
• ess than I Jm
Protocista Algae% proto!oa • Eu"aryotic
• 'enerally water
inhabitants
• Single$celled or
simple multi$cellular
#ungi Mould% yeast% mushrooms• Eu"aryotic
• Chitin cell wall
• Saprotrophic (absorb
substances fromdecaying organisms*
Plantae Mosses% ferns% floweringplants
• Eu"aryotic
• Multicellular
• Celluse cell walls
• Contain chlorophyll
• =hotosynthesis ability
• Autotrophic (produceown food*
Animalia 4nsects% fish% reptiles% birds%mammals% molluscs%nematodes
• Eu"aryotic
• Multi$cellular
• No cell walls
• 3eterotrophic
(consume plants K
animals*
Comparison of species
• Bossil records• 3omologous features
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• Evolutionary history
• DNA 8ase se/uence
• Ecological Niches
(ariation of genotype to )ariation of phenotype• 4ndividuals of a species have different genotypes.
• &his means a variation in phenotype , e/.
• 4dea that some characteristics are monogenic (controlled by one gene*.
• Reference to discontinuous variation , e)ample.
• 4dea that most characteristics are polygenic at different loci (controlled by many
genes*.
• Reference to continuous variation , e)ample .
0n)ironmental influences to phenotypes
• 3eight – polygenic.
• (by* nutrition , e)ample e1g1 malnutrition limiting child;s ma)imum height.
• Monoamine 2)idase A (MA2A* – monogenic.
• En!yme that +brea"s down , e/- monoamines.
• Reference to low levels of MA2A to mental health problems.
• Reference to antidepressants , tobacco reducing MA2A levels.
• Cancer.
• (by* diet.
• Animal hair colour.
• Seasonal , temperature influences , e)ample e1g dar" hair in summer but white hair
in winter.
• 'enes re/uired to trigger the change .
7iche
• Role of the species within its habitat.
• 4nteractions with other living organism , e)ample e1g1 prey and predators.
• 4nteractions with non$living environment , e)ample e1g1 gas e)change.
• reference to niche being uni/ue to species.
• reference to competition if two species occupy the same niche.
A d a p t a t i o n s
!ehavioural ,he way an organism acts to increase its chance of
survival and reproduction
*hysiological *rocesses inside an organisms $ody that increase chance
of survival
Anatomical ,hese are structural features of an organism-s $ody that
increase its chance of survival
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Adaptations
• idea of selection pressure , change in environment.
• reference to competition , predation .
• mutation #in conte,t$ .
• idea of advantageous allele.• idea that individuals with advantageous + alleles , characteristics , e/ - survive and
breed .
• idea of (advantageous* + allele , mutation - being passed on (to future generations* .
• idea of more individuals with this adaptation in the population , increased fre/uency
of advantageous alleles in the population
Biodiversity and endemism
8iodi)ersity
• #ariety of living organisms in an area
Species di)ersity
• Number of different species (in an area*
• Abundance of each species (in an area*
Genetic di)ersity
• #ariation of alleles within a species
Species richness
• the number of species .
• in +an area ,one location ,habitat- .
0ndemic
• idea that the ( species , e/ * is restricted in its distribution , species only found in one
specific + location , area , e/ -
1aitat
• &he area in which an organism lives
Measurement of species di)ersity
• Count the number of different species .
• &he higher the number of species% the greater the species richness .
• imitation – no indication of the abundance of each species .
• (so* Count the number of different species and number of individuals .
• @sage of biodiversity inde) , e/ .
Practical measurements of species di)ersity
•choose an area within the habitat to sample .
• idea that the sample is random .
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• idea of reduction of bias .
• count the number of individual species .
• aysL plants – /uadrat. airborne insects – sweepnet. ground insects – pitfall trap.
a/uatic animals – net .
• reference to repeats .
• Estimate total number of individuals or total number of different species .• idea of sampling techni/ue being the same .
Measurement of genetic di)ersity
• 'enetic diversity is the variety of alleles in the gene pool of a species.• &he gene pool is the complete set of alleles in a species
• &he greater the variety of alleles% the greater the genetic diversity
• Measured by phenotype.
• idea that different alleles code for different versions of the same characteristics.
• arger the number of phenotypes% the greater the diversity.
• Measured by genotype.
• Se/uence of 8ase pairs in DNA analysed.
• 2rder of bases in alleles is different.
• 8y se/uencing DNA% similarities and differences are observed.
• arger the number of alleles% the greater the genetic diversity
Reduction of genetic di)ersity
• Reduced variety,number of different alleles,DNA , reduced gene pool (in new
population*.
• Bounder effect.
• A few individuals from a population become isolated,form colonies
• ('enetic* bottlenec"s.
• (Significant* fall in si!e of population
• Selective breeding , artificial selection.
@sing organisms with particular alleles,traits,phenotypes,characteristics.
6mportance of storing seeds rather than plants
• ta"e +less , smaller- space , e/ .
• can have more individuals , e/ .
• reference to +greater , more- genetic variety .
• idea of less +maintenance , cost- .
• li"ely to survive longer , e/ .
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• can free!e seeds , e/ .
6mportance of storing seeds from different plants
• idea of +greater , maintain- genetic variety
• e1g1 wider gene pool% different alleles .
• idea of less chance of inbreeding .• idea of reducing chance of storing seeds with
• +low viability , disease , e/- .
Seeds of different si9es
• idea of maintaining or increasing +genetic diversity , si!e of gene pool , genetic
variation- .• idea of more chance of having beneficial alleles ,e/ .
• increases chance of future survival +if environment changes , due to higher
adaptability - , e/ .
• less chance of all being susceptible to a disease , e/ .
1o! 9oos maintain the genetic di)ersity of endangered species
• breeding programme , e/ .
• careful selection of mate , e/ .
• allowing only to mate with a different individual to previous mating , e/ .
• only allowing those with different genes to mate , e/ .
• use of genetic testing , e/ .
• record "eeping (studboo"s* .
• reason for outbreeding .
• reintroduction to the wild , e/ .
Seedan" conser)ation
•
details of assessment of seed viability e1g1 only select seeds with a living embryo%use of > ray (to detect embryo presence* , e/ .
• idea of +cleaning seeds , surface sterilisation , e/- .
• idea of drying (of the seed* .
• idea of storing at low temperatures .
• idea of regularly testing viability (during storage of seed* .
• idea of what to do if viability decreases% e1g1 if less than I germinate collect fresh
seed for storage
Prolems !ith re,introduction and capti)e reeding
• idea that conditions are difficult to re$create in captivity , li!ards won;t breed , e/ .
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• ethical issues /ualified e1g1 cruelty , immorality .
• reintroduced species could bring disease .
• idea that the reintroduced species may not retain their natural behaviours in the wild .
Sexual reproduction
4ays in !hich a human sperm cell is specialised for its function
• shape /ualified e1g1 hydrodynamic% streamlined .
• idea of reduced resistance .
• +acrosome , 8esicle- containing +en9'me , acrosin-.
• involved in +digestion , brea" down- of the +9ona pellucida ,
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Role of digesti)e en9ymes for the style
• idea of +brea"down , digestion , e/- of style .
• (brea"s down* protein , pectin , middle lamella .
• reference to hydrolysis , e/ .
• easier for pollen tube to grow , reduced resistance , e/ .
• supplies +nutrients , named nutrient , energy-• for (pollen tube* growth , e/ .
Crossing o)er
• (before 9st meiotic division* homologous pairs of chromosomes pair up
• chromatids +twist , tie , e/- around each other .
• +bits , parts , e/- of the chromatid brea" off and
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• tube nucleus +disintegrates , brea"s down , e/-and tip of pollen tube bursts to release
7 male nuclei .
• one nucleus fuses with egg nucleus to form a !ygote.
• division by mitosis to form embryo.
• other male nucleus fuses with two other polar nuclei at the centre of the embryonic
sac to form triploid nucleus.• large nucleus forms to become a food store called endosperm .
• reference to double fertilisation
Stem Cells
Totipotent stem cell
• totipotent (stem cells* can give rise to +all , any , 79:- cell types , e/ . 1
• (stem cells* are +undifferentiated , unspecialised- , e/ .
• can "eep dividing , e/ .
•
only present in early life of embryo .• no genes switched off .
Pluripotent stem cell
• =luripotent (stem cells* can give rise to +all , any- cell types , e/ .
• E>CE=& e)traembyronic cells .
ote " first point must %e linked with second to earn marks
Differentiation
• &he process by which a cell becomes specialised .
-ocation of stem cells
• Embryo – differentiate into all cells needed to form a fetus .
• Adult tissues e1g1 bone marrow .
Differential gene e2pression , enaling cells to ha)e different structures andfunctions3
• different genes active in different cells , different genes
• active at different times , some genes +active , inactive- , e/ .
• active genes ma"e mRNA , e/ .
• active genes ma"e proteins , polypeptides ,e/ .
• (proteins* control cell +processes , e/- .
• idea of permanent change (to cell* , e/
8enefits
• Replace damaged tissues (in diseases* .
• credit e)ample e1g1 nerve tissue for spinal cord or heart tissue for heart$related
diseases .
• idea of saving many lives e1g1 growth of organs for those waiting for transplants .
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• idea of /uality of live being improved e1g1 replacing damaged cells in eyes in blind
people .
Adult stem cells multipotent'
•
body tissues of an adult e1g bone marrow .• simple operation but discomfort to patient .
• needle into centre of a bone .
• small /uanity of bone marrow removed .
• idea that adult stem cells +are not fle)ible , are limited in use , e/- .
0mryonic stem cells
• 2btained from early embryos
• Embyros created in 4#B lab , e)plained
• Stem cells removed after 6$I days
• Embryos destroyed .
• idea that embryonic stem cells can develop into +all , any , 79: , e/- cell types .
• more li"ely to cause immune re
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• 'uidelines , codes of practice to ensure scientists are wor"ing in a similar manner .
• Monitoring developments in research to ensure any changes are regulated and
guidelines are up$to$date.
• =roviding advice,information to the government and professionals to promote the
science involved in the research% and aid society in understanding the benefits
Experiment-based questions
Oser)ing mitosis
• Cut OImm tip from a growing root.
• =lace root on a watch glass% then add hydrochloric acid.
•
Add drops of stain to dar"en chromosomes and ma"e them more visible undermicroscope (credit e)ample. e1g1 toluidine blue*.
• arm watch glass using a 8unsen burner.
• =lace root tip on a microscope slide.
• @se a mounted needled to brea" the tip open and spread it evenly.
• Add more drops of stain and place a cover slip over it.
• S/uash the cover slip.
• arm slide to intensify stain.
• Repeat e)periment to increase reliability.
Totipotency & Tissue Culture
• Single cell ta"en from a growing area (credit e)ample – e1g1 root*
• idea that cell is placed in a sterile growth medium.
• idea that the growth medium contains nutrients and growth hormones.
• plant cell will +grow , divide , e/- into unspecialised cells .
• idea that unspecialised cells will differentiate into specialised cells if the conditions
are optimum
• Cells will grow and differentiate into an entire plant
Plant tensile strength
• Attach each of the four fibres to a clamp stand at one end.
• 3ang weights from other end.
• Add one weight at a time to the fibres until they brea"
• Record the mass ta"en to brea" each fibre.
• More mass greater tensile strength.
• Repeat e)periment to increase reliability.
• Heep variables constant – such as length of fibres% temperature% and humidity.• =rotective gear must be worn.
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8/18/2019 Edexcel Bio 2 Notes (1)
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6n)estigating plant mineral deficiencies ;anuary ?'
•
4dea of genetically similar plants e1g1 clones% cuttings% e)plants or seedlings fromsame parent plant .
• plants all of same + age ,si!e - (at start* .
• reference to at least five nutrient broths with different (nitrate* concentrations .
• sensible range of different nitrate concentrations either side of and including 7PP
(ppm* .
• correct reference to any t!o abiotic variables that need to be "ept constant (volume
of mineral solution , si!e of container , amount of light* .
• idea of sensible measure of growth e1g1 mass , number of leaves , length of roots
,height of plant .• time allowed for growth + wee"s , months -.
• appropriate reference to repeats% e1g1 replication at each concentration or repeating
the whole e)periment
Anti,microial properties of plants
• &a"e plant e)tract by drying and grinding.
• Soa" in ethanol.
• Bilter li/uid bit.• Evenly spread bacteria on +agar , nutrient plate , e/-.
• Dip disc of absorbent paper in plant e)tract.
• Soa" a disc in ethanol to act as a control.
• =lace discs on plate% widely apart.
• 4ncubate plate to allow bacterial growth.
• idea that an +inhibition !one , clear patch , e/- (on the lawn of the bacteria* will be
present if plant has antimicrobial properties.
• no inhibition !one should be present on control disc.