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Mark Scheme (RESULTS)January 2008

GCE

GCE Biology (6101/01)

Edexcel Limited. Registered in England and Wales No. 4496750Registered Office: One90 High Holborn, London WC1V 7BH

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1

Statement Glycogen Cellulose

Consists of glucose X

Contains 1,4 glycosidic bonds

Is a branched molecule X

Is a structural carbohydrate X

Any two correct boxes for one mark

max4

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2 1. (simple ) diffusion ;

2. facilitated diffusion ;

3. active transport ;

4. ATP ; 4

1 Unit 1

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2

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3 (a)(i) the {sequence / order} of amino acids ; 1

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3 (a)(ii) hydrolysis ; 1

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3 (b)

CCNH

HH

O

OHCH 2

OH ; 1

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3 (c)Collagen Insulin

1. fibrous globular ;

2. three {polypeptide chains} /triple helix

two {polypeptide chains} /reference to A and B chains ;

3. chains not held together bydisulphide bonds / chains heldtogether by hydrogen bonds

chains held together bydisulphide bonds / eq ;

4. large / about 1000 aminoacids OR length can bevariable

small / 51 amino acidsOR fixed / precise length ;

5. repetitive / repeatingsequence / eq

no repetitive sequence ; max3

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4

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5 (a)(i) cell in anaphase correctly identified ; 1

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5 (a)(ii) cell in telophase correctly identified ; 1

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5 (a)(iii) 2 / 3 ; 1

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5 (b) 1. idea that during prophase {chromosomes / chromatids} (becoming)

visible ;

2. idea of centrioles move to opposite poles ;

3. reference to formation of {spindle /spindle-fibres /

microtubules} ;

4. disappearance of nucleolus / nucleoli ;

5. breaking down of nuclear {envelope / membrane} (in prophase) or

nuclear envelope is broken down by metaphase / eq ;

6. (at metaphase) {chromosomes / centromeres} attached to spindle

(fibres) ;

7. idea of {chromosomes / chromatids} lined up at equator ; max5

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5

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6 (a) 1. {envelope / double membrane} clearly shown ;

2. granum clearly shown ;

3. {granum / thylakoid(s)} labelled ;

4. {stroma / ribosomes / starch grain / DNA / lipid droplet / {double/ inner / outer} membrane / envelope / intergranal lamellae}correctly labelled ; 4

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6 (b)(i) 1. correct length ;

2. divided by 50 000 ;

3. correct length in m ; 3

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6 (b)(ii) vacuoles / vesicles / lysosomes / glycogen granules / ribosomes / lipiddroplets / centrioles / spindle fibre / microtubules ; 1

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6 (b)(iii) {resolution not high enough / eq} / damage / {angle of section / eq} / {poorprinting of photograph / eq} ; 1

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6

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7 (a) 1. reference to use of {iodine solution / iodine in potassium iodide} ;

2.

{observation / colour change} described ;3. credit any valid experimental details ; 3

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7 (b) 1. overall decrease in activity ;

2. increasing concentration up to 4 au increases the activity of amylase ;

3. increasing concentration from 4 au (to 32 au) reduces activity ;

4. reference to change in activity at 20 au ;

5. correct manipulation of data ;max3

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7 (c) 1. {copper ions / inhibitor} block the active site / eq ;

2. idea that inhibitor is the same shape as substrate ;

3. preventing {starch / substrate} binding with {amylase / active site /enzyme} ;

4. the more {copper ions / inhibitor} the more active sites are blocked ;

5. reduces enzyme activity / eq ;max3

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7

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7 (d)(i) 1. it allows a comparison to be made (with and without copper ions) ;

2. reference to {starch / substrate} concentration being the same (withand without copper ions) ;

3. the rate of reaction changes with time /eq ;

4. because substrate is being used up / eq ;max2

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7 (d)(ii) idea that the {maximum rate/ V max } (with copper ions present) is lower (thanwithout inhibitor) / if it was active site-directed it would take longer to reachsame maximum rate ; 1

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8

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8 (a) A phosphateB deoxyribose ; 1

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8 (b)(i) Adenine 29, Guanine 21, Cytosine 21 ; 1

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8 (b)(ii) 1. a purine always bonds to a pyrimidine ;

2. % thymine must equal % adenine / eq ;

3. guanine and cytosine must make up rest of molecule / eq ;

4. % guanine = % cytosine / eq ;max3

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8 (c) 1. DNA contains genetic information / eq ;

2. DNA codes for protein / eq ;

3. a change in DNA could produce a different {protein / mRNA} / eq ;

4. idea that it is required throughout life (or {cell / organism} ) ;

5. idea that it is needed to pass on to next generation (of {cell /organism}) ;

max2

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1 1. monocytes ;

2. antibodies / immunoglobulins ;

3. eosinophils / basophils ;

4. nucleus ; 4

2 Unit 2

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2 (a) A red blood (cell) / erythrocyte ;

B (alveolar) epithelial cell / epithelium / squamous epithelium / ; 2

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2 (b) 1. {thin / eq} cells ;

2. decreases diffusion distance ;

3. permeable (to respiratory gases) ;

4.

(collectively) have a large surface area ;5. increases diffusion ;

6. of respiratory gases / oxygen / carbon dioxide ;

7. (surrounded by) capillaries ;

8. idea that movement of blood maintains {diffusion / concentration}gradient ;

9. reference to {the presence of / a description of} surfactant ; max4

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2 (c) 8.1 (dm 3) ; 1

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3 (a) Carbohydrate Enzyme Products

amylase ;

glucose andgalactose ;

sucrose ; sucrase ;4

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3 (b) 1. reference to active uptake / active transport (of glucose) ;

2. reference to sodium-glucose co-transport ;

3. reference to (specific) glucose carrier proteins / fewer transportproteins for fructose / more transport proteins for glucose /fructose is absorbed by diffusion (only) ; 3

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4 (a) A aorta / aortic arch ;

B (right) atrioventricular valve / tricuspid valve ; 2

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4 (b) 1. reference to coronary circulation ;

2. reference to coronary artery / coronary arteries ;

3. reference to capillaries (in wall of heart) ;

4. oxygen {transported / eq} by {red cells / haemoglobin} ;

5. oxygen diffuses out of {blood / red cells / capillaries} (to heartmuscle) ;

max3

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4 (c) 1. pacemaker / SAN sends {impulse / eq} (to atria) ;

2. {causing/ eq} atria to contract ;

3. {impulse / eq} reaches AVN ;

4. reference to delay at the AVN ;

5. idea that the impulse travels to ventricles via {bundle of His /Purkyne tissue / eq} ;

max3

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4 (d) 1. increased {demand for / eq} {oxygen / glucose} / increasedrespiration ;

2. increased heart rate / heart beats faster / eq ;

3. increased stroke volume / cardiac output ;

4. increased production of carbon dioxide ;

5. reference to dilation of blood vessels in muscle ;

6. reference to adrenaline ;max3

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5 (a)(i) 1. presence of gills ;

2. to increase surface area / increase uptake of oxygen ;

3. presence of haemoglobin / respiratory pigment ;

4. with high affinity for oxygen ;

5. presence of siphon / (breathing) tube / eq ;

6. to obtain oxygen (directly) from the air ;

NB paired points

max4

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5 (a)(ii) 1. presence of claws / hooks / suckers ;

2. to attach to substrate / eq ;

3. {flattened / streamlined / eq} body /reference to burrowing ;

4. less resistance to water flow / less likely to be washed away ;

NB paired points

max2

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5 (b) 1. inverse relationship / eq ;

2. credit a manipulated quantitative comment ; 2

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6 (a) 1. insect ;

2. large petals / coloured petals ;

3. scent / nectar / nectary ;

4. to attract insects ;

5. correct reference to position of anthers ;

6. correct reference to position of stigma ; max3

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6 (b) 1. increased (from 30) to 90 minutes ;

2. decreased from 90 (to 180) minutes ;

3. reached a max. at 90 minutes / reached a peak at 90 minutes ;

4. credit a manipulated quantitative comment ;max3

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7 (a) xylem (vessel) ; 1

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7 (b) 1. endodermal cells have Casparian strip ;

2. reference to {suberin / eq} ;

3. which is waterproof / eq ;

4. stops movement of water in apoplast pathway / description ;

5. water directed into symplast pathway / description ;

6. reference to {control of uptake / active transport of ions (intoxylem)} ;

max3

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7 (c)(i) 1. concentration increases as temperature increases / eq ;

2. credit a manipulated quantitative reference ; 2

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7 (c)(ii) 1. uptake is active / eq ;

2. concentration in cells is higher than concentration in solution /converse ;

3. ions are taken up against concentration gradient ; 3

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8 (a) E D C B A ;;

NB All correct = 2 marks, 1 error (i.e. one letter out of sequence) = 1 mark 2

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8 (b) (i) 46 ;(ii) 23 ; 2

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8 (c) 1. {primordial (germ) cells / oogonia} divide by mitosis ;

2. oogonia (develop to) form primary oocytes ;

3. primary oocytes divide by meiosis I ;

4. to form a secondary oocyte ;

5. and a polar body ;

6. secondary oocyte divides by meiosis II ;

7. to form an ovum ;max4

PAPER TOTAL: 60 MARKS

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1 (a)(i) 1. reference to external digestion /eq ;

2. feed on organic material / both are heterotrophic /eq ;

3. reference to hypha(e) {secrete / eq} enzymes / absorb {digestedproducts / named product} / eq ;

max2

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1 (a)(ii) 1. (Rhizopus ) is {saprobiontic / saprophytic} / eq ;

2. (Rhizopus ) {feeds on / eq} {dead / eq } material ;

3. reference to importance of Rhizopus as {a decomposer / involved inrecycling of nutrients} and Phytophthora causing {harm / loss of crops/ eq} ;

max2

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1 (b) 1. {less / eq} photosynthesis possible ;

2. (because) {leaves / palisade cells / photosynthetic cells /chloroplasts} damaged / eq ;

3. less {glucose / starch / organic compounds} produced /eq / idea of fungus using up the plants organic material ;

4. reference to {blocked stomata / inefficient gas exchange / eq} ;max2

3 Unit 3

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2 (a) 1. bacteria / fungi / saprophyte / saprobiont / decomposer / suitable,correct organism ;

2. reference to respiration ; 2

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2 (b)(i) photosynthesis ; 1

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2 (b)(ii) 1. reference to respiration (of some of the organic material) ;

2. idea that energy is required ;

3. for synthesis of {molecules / eq} / movement / active transport} ;max2

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2 (c) 1. idea of {carbon / carbon dioxide} {locked away / stored} / eq ;

2. for {many years / a long time / eq} ; 2

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2 (d) 24 391 37.98 ;

642.2 x 10 6 ha ; 2

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2 (e) 1. (different) {climates / rainfall / temperatures / eq} ;

2. (different) {species / types} of {tree / forest} ;

3. (different) {ages / maturity / size / eq} of forests ;

4. (different) tree density / number of trees ;

5. reference to (different) day lengths ;

6. reference to (different) light intensity ;

7. (different) carbon dioxide concentration / eq ;

8. any two other valid reasons ;;max2

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2 (f) 1. idea of less carbon dioxide {fixed / taken up / eq} by photosynthesis ;

2. {respiration / combustion of {fossil fuels / trees}} continues to releasecarbon dioxide ;

3. carbon dioxide builds up in {upper atmosphere / troposphere} ;

4. reference to carbon dioxide as greenhouse gas ;

5. description of the greenhouse effect ;

6. reference to {enhanced / eq} greenhouse effect ;

7. reference to global warming / increase in mean temperature (of Earths surface) ;

max4

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3 (a)(i) {total biomass / eq} produced / {total energy / eq} taken in ;

by {plants / producers / photosynthesis / eq} ; 2

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3 (a)(ii) 1. light intensity ;

2. light duration / eq ;

3. light wavelength ;

4. temperature ;

5. {carbon dioxide / carbonate} concentration ;

6. pH ;

7. named aquatic pollutant ;max2

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3 (b) 1. (dead plant material) is decomposed / eq ;

2. by action of {bacteria / microoorganisms / eq} ;

3. idea that aerobic respiration involved ;

4. (more) dead material provides more nutrients which leads to anincrease in microorganisms / eq ;

max3

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3 (c)(i) 1. CR in winter {usually greater/eq} than in summer ;

2. both show increase as distance (from headwaters) increases ;

3. in winter CR increases {greatly / eq}, in summer only {slight increase /eq} ;

4. use of manipulated data ;max2

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3 (c)(ii) 1. idea that {more leaves / detritus / eq} added with distance fromsource / more leaves shed in winter / (more dead material because)algae die down in winter ;

2. far increased {bacterial / eq} activity ; 2

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3 (d)(i) 1. GPP {increases as distance (from headwaters) increases / higher inMotueka River} ;

2. high GPP indicates {high algal population / eq} ;

3. (because) algae release oxygen by photosynthesis ;

4. more algae means more {grazing invertebrates / eq} ;

5. more food (for fish / trout) ;max3

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3 (d)(ii) 1. CR {higher / increases} (in winter) ;

2. (higher CR indicates) more {detritus / eq} ;

3. {algae / eq} may die down in winter ;

4. reference to {decay / eq} (of detritus and/or algae) uses up oxygen ;

5. fish population {falls / eq} ;max3

TOTAL FOR PAPER: 38 MARKS

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1 (a) Time of day Cushion temp./ 0C

Mean cushiontemp. / 0C

Air temp. / 0C

08.00 8,9,8 8.3 (8.33) 410.00 17,15,15 15.7 (15.67) 712.00 20,22,23 21.7(21.67) 914.00 21,21,22 21.3 (21.33) 1116.00 19,17,20 18.7 (18.67) 918.00 6,5,5 5.3 (5.33) 3

suitable table with time, mean cushion temp and air temp ;

correct rows and columns with headings and units ;

means correct to consistent sig. figs. (all correct = 2 marks, one error = 1mark);;

max4

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1 (b) F line graph format with both lines on same axes ;

A axes correct orientation and labelled with suitable scale ;

P points plotted correctly ;

L straight line joins points or good curve through all points ; 4

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1 (c) 1. cushion temperature always above air temperature ;

2. as air temperature increases ANDdecreases so cushion temp increasesANDdecreases ;

3. some relevant use of figures e.g. maximum cushion temp. 10.3 0Chigher than maximum air temp. ;

4. temp / max cushion temp. almost double max air temp. / eq ;max2

W1 Unit 3

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1 (d) 1. no evidence of any significant anomalies / cushion temp. falls eventhough air temp. continues to rise ;

2. random cushion readings do not vary by more than 3 0C / cushion airtemp. anomaly quantified ; 2

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1 (e) 1. reference to higher temperature promoting metabolism (e.g. enzymeactivity, photosynthesis) ;

2. growing points / meristems can be protected from temperatureextremes inside cushion ;

3. ref to reduction in surface area / eq ;max2

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2 (a) Points 1 & 2: reference to initial seeds/seedlings at start of study

Points 3 & 4: ex traction of root nodules material (from established plants)

Points 5 & 6: selection of seedlings for inoculation

Points 7 to 13 : design, growth parameters and measurement

1. use of stated leguminous plant / member of Papilionaceae forstudy (e.g. clover) ;

2. {germinate / grow} {seeds / seedlings} in two named standardconditions ;

3. remove nodules (from established plant of same species) ;

4. suitable method of extraction of constant concentration of inoculum (e.g. {grind / eq} stated mass of root nodules in statedvolume of water) ;

5. stated number (5 or more) of {seedlings / seeds} for each trial ;

6. seedlings / eq / seeds {same size / same mass / measuredparameter} at start ;

7. preparation of concentrations described (e.g. named nitrogensource / nitrate / ammonium salt / fertiliser e.g. 1 g in 100 cm 3) ;

8. same volume of nitrogen source (in every case) ;

9. 5 or more concentrations of nitrogen source used ;

10. suitable (control) with no nitrogen added (e.g. using distilledwater) ;

11. seedlings grown for stated period (minimum 1 week) ;

12. {count number / obtain {wet / dry} mass of root nodules} ;

13. minimum of 2 repeats (i.e. three trials in total) ; max9

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2 (b) 1. suitable table of raw data, with correctly labelled rows and columns,including units to match the method ;

2. line graph / bar chart ;

3. correctly orientated and labelled axes including units ;

4. calculation of means ; max3

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2 (c) Limitations: [Sub-maximum 4]

1. difficult to know if (original nodules / extract) contain living bacteria;

2. difficult to know if {seeds / growth medium} already containRhizobium ;

3. difficult to get {seeds / seedlings} {to take up bacteria to developnodules} ;

4. environmental conditions inhibit {formation of nodules (if notcontrolled) / enzymes (of Rhizobium ) ;

5. difficult to collect / count all root nodules ;

Further work: [Sub-maximum 4]

6. the effects of root nodules / leguminous plants on the growth of cropplants per se ;

7. test effect of different concentrations of inoculant ;

8. the effects of different species of legume and fertiliser on plantgrowth / crop production ;

9. the effect of root nodules and types of fertiliser on the growth of other legumes / eq ;

10. a named environmental condition on root nodule formation ;

11. undertaking field trials into the relationship between Rhizobium ,fertilisers and crop production ;

max6