Movement of Substances in and out of Cells

Transcription

1 Movement of Substances in and out of Cells Mark Scheme Level Subject Exam Board Unit Topic Difficulty Level Booklet GCSE Biology AQA B3 Movement of Substances in and out of Cells Gold Level Mark Scheme Time Allowed: 46 minutes Sce: /46 Percentage: /00 Page

2 M.(a) (i) has the least amount of glucose allow least amount of fat no fat (to) transfer energy (f the run) allow (to) release energy (f the run) do not allow produces energy do not allow energy f respiration any one from: cells will wk inefficiently absb too much water / swell / overhydrate lose too much water / shrink / dehydrate igne turgid / flaccid cells burst is insufficient allow cramp in muscle. (b) any three from: thermegulaty centre (has temperature) recepts (which) monit blood temperature (as it flows through the brain) (temperature) recepts in the skin (recepts) send impulses to the brain igne vasoconstriction / vasodilation / sweating allow hypothalamus impulses sent to the thermegulaty centre = 2 marks. 3 (c) (i) (spts drinks) contain a lot of glucose (a person with diabetes) does not produce insulin does not produce enough insulin allow (person with diabetes) has cells which do not respond to insulin do not allow insulin produced by liver so blood glucose / sugar levels will rise too high to a dangerous level inject insulin Page 2

3 have an insulin pump (fitted) do not allow swallow insulin accept exercise accept inhale insulin accept take metfmin other crectly named drug allow pancreatic transplant [0] M2.(a) (i) diaphragm accept phonetic spelling (because) the volume (inside the jar) increases maximum two marks if no reference to crect part of model (causing) the pressure to decrease (and) air enters the balloon allow oxygen (b) (i) (so it moves by) diffusion do not allow osmosis active transpt from a high concentration (of oxygen) to a low concentration allow down its / oxygen concentration gradient from the air to the blood (because) there is a high(er) concentration (of oxygen) in the air there is a low(er) concentration of oxygen in the blood igne reference to amount of oxygen many gill filaments must be in the crect pairs to gain 2 marks (give a) large surface / area do not allow surface area to volume ratio thin Page 3

4 (so) sht diffusion pathway good blood supply (to) maintain the concentration gradient water continually flows over them / continually ventilated (to) maintain the concentration gradient [8] M3.(a) B no mark f B alone, the mark is f B and the explanation. large(r) surface / area large(r) membrane accept reference to microvilli igne villi / hairs / cilia accept reasonable descriptions of the surface eg folded membrane / surface do not accept wall / cell wall (b) (i) any one from: (salivary) amylase carbohydrase many ribosomes do not mix routes. If both routes given award marks f the greater. ribosomes produce protein accept amylase / enzyme / carbohydrase is made of protein (allow) many mitochondria () Page 4

5 mitochondria provide energy to build / make protein () accept ATP instead of energy [4] M4.(a) both parents Aa accept other upper and lower case letter without key symbols with a key allow as gametes shown in Punnett square aa in offspring crectly derived from parents aa crectly derived from the parents given igne other offspring / gametes f this mark parents do not have to be crect offspring aa identified as having cystic fibrosis may be the only offspring shown circled / highlighted / described (b) (i) any one from: accept converse if clear, eg if you (only) took one it might have cystic fibrosis / might not be fertilised (me) sure / greater chance of healthy / non-cystic fibrosis egg / embryo / child accept some may have the allele reference to suitable / good embryo is insufficient greater chance of fertilisation advantages to gain 3 marks both advantage(s) and disadvantage(s) must be given Page 5 max 3

6 any two from: igne references to abtion unless qualified by later screening greater / certain chance of having child / embryo without cystic fibrosis / healthy child with cystic fibrosis difficult / expensive to bring up cystic fibrosis (gene / allele) not passed on to future generations disadvantages any two from: operation dangers / named eg infection igne risk unqualified ethical religious issues linked with killing embryos accept wrong / cruel to embryos accept right to life argument igne embryos are destroyed (high) cost of procedure possible damage to embryo (during testing f cystic fibrosis / operation) plus conclusion a statement that implies a qualified value judgement eg it is right because the child will (probably) not have cystic fibrosis even though it is expensive eg it is wrong because embryos are killed despite a greater chance of having a healthy baby note: the conclusion mark cannot be given unless a reasonable attempt to give both an advantage and a disadvantage is made do not award the mark if the conclusion only states that advantages outweigh the disadvantages (c) any three from: osmosis / diffusion Page 6

7 do not accept movement of ions / solution by osmosis / diffusion me concentrated solution outside cell / in mucus assume concentration is concentration of solute unless answer indicates otherwise accept crect description of water concentration water moves from dilute to me concentrated solution allow crect references to movement of water in relation to concentration gradient partially permeable membrane (of cell) allow semi / selectively permeable 3 [] M5.(a) solution in soil is me dilute (than in root cells) concentration of water higher in the soil (than in root cells) so water moves from the dilute to the me concentrated region so water moves down (its) concentration gradient water moves from a high concentration of water to a lower concentration concentration of ions in soil less (than that in root cells) so energy needed to move ions ions are moved against concentration gradient the direction of the concentration gradient must be expressed clearly accept crect reference to water potential to concentrations of water (b) any three from: movement of water from roots / root hairs (up stem) via xylem Page 7

8 to the leaves (water) evapates via stomata 3 (c) (i) 0.67/0.7 accept 0.66, ⅔ 0.6 crect answer gains 2 marks with without wking if answer increct allow evidence of do not accept f mark 2 during the first 30 minutes any one from: it was warmer it was windier it was less humid there was me water (vapour) in the leaves. so there was me evapation igne water loss stomata open during first 30 minutes closed after 30 minutes () so faster (rate of) evapation in first 30 min reducing (rate of) evapation after 30 min () [] M6.(a) oxygen / O 2 allow O 2 do not accept O 2 Page 8

9 carbon dioxide / CO 2 allow CO2 do not accept CO 2 (b) any four from: igne references to tail used f locomotion igne reference to nostrils because structure X / gills has threads / filaments is thin tadpole has longer tail there is an increased surface area there is a shter diffusion pathway therefe an increase in exchange igne food eyes (now visible in older tadpole) so that food / danger etc can be seen accept reference to a good blood supply accept increased water flow over gills / tail will increase diffusion of gases 4 [5] M7. (a) water enters (funnel / sugar solution) water diffuses in (to the funnel) do not accept if diffusion of sugar membrane partially / selectively / semi permeable by osmosis allow description because concentration (of sugar) greater inside funnel than outside / water / in beaker assume concentration refers to sugar unless candidate indicates otherwise the position of the solutions may be implied Page 9

10 (b) (level / it) rises me slowly levels out earlier does not rise as much accept inference of less steep gradient (of graph) allow less / slower osmosis / diffusion / less water passes through less water enters funnel allow water enters / passes through slower less difference in concentration (between solution / funnel and water / beaker) accept due to lower diffusion / concentration gradient / described [5] M8. (a) (i) diffusion is down the concentration gradient f a description of diffusion igne along / across gradients to enter must go up / against the concentration gradient accept by diffusion ions would leave the root concentration higher in the root / plant concentration lower in the soil active transpt allow active uptake Page 0

11 (b) (i) (root hairs ) large surface / area (aerobic) respiration do not allow anaerobic releases / supplies / provides / gives energy accept make ATP (f active transpt) do not allow makes / produces / creates energy (iii) starch is energy source / ste (f active transpt) allow starch can be used in respiration do not allow makes / produces / creates energy [7] M9. (a) crect names of cell components are required it = cell in sugar solution any two from: accept reverse only if clearly stated answer refers to cell in distilled water smaller vacuole smaller / less cytoplasm allow protoplasm f cytoplasm cell membrane / cytoplasm not (fully) against cell wall accept plasmolysed / flaccid / less turgid cell membrane / cytoplasm (partly) pulled away from cell wall igne reference to nucleus / water igne explanations Page

12 space / liquid / sugar solution between cell membrane / cytoplasm and cell wall 2 (b) water passed / moved out (of cell) by osmosis / diffusion accept reverse answer if clearly refers to cell in distilled water me concentrated (solution) outside assume reference to concentration refers to solute concentration unless answer refers to water concentration less concentrated (solution) inside lower water concentration outside accept references to hypertonic / hypotonic solutions water potential higher water concentration inside [4] M0. active transpt needs energy diffusion is not energy-dependent any three from: (energy from) aerobic respiration me respiration with O 2 me energy release with O 2 (aerobic) respiration / energy release occurs in mitochondria do not allow anaerobic xylose / other sugars absbed by diffusion / not by active transpt Page 2

13 allow active transpt is selective / specific active transpt can distinguish glucose and xylose 3 [4] M. only 24 students tested only one test reference to lack of controls eg gender / age students could drink as much water as they wanted some students drank me water than others some students drank water and beer differences only slight igne effects of beer promotion of beer drinking [3] M2. (a) (i) movement of atoms / molecules / ions accept particles allow dissolved substances igne reference to membranes (substance) moves from high to low concentration allow down the gradient igne Page 3

14 across / along / with a gradient any two from: movement of molecules / ions accept particles allow dissolved substances this point once only in (a)(i) and (a) from low to high concentration allow up / against the gradient igne across / along / with a gradient requires energy / respiration accept requires ATP 2 (b) filtration of blood described re small (molecules)through / large not igne diffusion max four from: reabsption / substances taken back into blood (reabsption) of all of the sugar / glucose (reabsption) of some of ions / of ions as needed by body (reabsption) of some of water / of water as needed by the body urea present in urine accept urea not reabsbed reabsption of water by osmosis / diffusion reabsption of sugar / ions by active transpt 4 [9] Page 4

15 M3. (a) (i) glucose and galactose any three from: Evidence: absption reduced by cyanide allow converse absb faster (than other sugars) Explanation: active transpt needs energy less / no energy available / released if cyanide is there less / no energy if no / less respiration allow energy produced igne cyanide prevents respiration 3 (b) all / the sugars / they can be absbed when gut poisoned / with cyanide when no respiration (diffusion) does not need an energy supply [6] M4. (a) guard (cell) igne stoma / stomata Page 5

16 (b) Species A: stomata open in dark / at night close in light / in day stomata closed during warm(est) period open when cool(er) heat (energy) / warmth increases evapation / transpiration must give explicit link between heat and transpiration reduces water loss / evapation / transpiration igne photosynthesis allow converse points f species B [5] M5. (a) No no mark if yes max f crect statement diffusion is down the concentration gradient accept by diffusion ions would leave the root to enter must go up / against the concentration gradient concentration higher in the root concentration lower in the soil (b) (i) f crect answer with without wking if answer increct.3 their rate 0.4 gains mark gains mark 2 (uptake) by active transpt Page 6

17 requires energy me energy from aerobic respiration me energy when oxygen is present [7] M6. (a) any two from: transpt up / against concentration gradient / low to high concentration uses energy use of protein / carrier 2 (b) microvilli large(r) surface area accept have carriers mitochondria release energy make ATP do not accept makes energy [4] M7. (i) in diffusion: material moves high to low concentration here: concentration in cells > concentration in water uptake is against the concentration gradient by diffusion ions would move out Page 7

18 active transpt / active uptake [3] M8. thicker surface reduced surface area accept fewer alveoli [2] M9. (a) (i) change in weight was due to changes in potato osmosis not due to outside liquid igne to make fair test beaker 2 = 5.(%) gain allow 5% beaker 4 = 2.8(5) loss not 2.7 allow 22% if no minus no loss check graph beaker 5 = 29.8(%) loss allow 30% Page 8

19 (b) (i) both axes crect values and scales > ½ of each axis igne lack of minus signs on vertical axis points crect < ½ square allow answers in (a) line crect allow curve of best fit which can miss 0, 5 straight lines between points do not allow one straight line sketched line bar graph zero marks point where line crosses axis (eg 5-6% sucrose) allow point from candidate s graph ( 0.5%) (iii) any two from: looking f understanding that water in equilibrium no change in mass not net movement of water water entry and exit are equal because sucrose solution same concentration as cell sap sucrose has same water potential as cell contents allow because the concentrations are the same (inside and out) 2 [0] Page 9

20 M20. ideas that sugar has dissolved in moisture (on surface of fruit) this solution me concentrated than solution inside fruit osmosis / diffusion movement of water out of fruit through partially permeable membrane (of fruit cells) any four f mark each allow explanations in terms of concentrations of water molecules f full marks [4] M2. (a) (i) A B f mark each 2 (b) diffusion (reject osmosis) f one mark (c) C because uptake against a concentration / diffusion gradient (reject osmosis) (if C not given, then idea of movement essential) f mark each 2 [5] M22. (a) allow carbon dioxide to enter / gaseous exchange (oxygen neutral) (transpiration neutral) Page 20

21 f one mark (b) guard (cells) f one mark (c) stops / reduces the rate of water loss / transpiration (reject if dark initiated) stops / reduces wilting / description e.g. drooping / maintains turg f mark each 2 [4] M23. (a) (i) water (molecules) enter(s) (the cell) water (molecules) pass(es) through the (semi-permeable) cell membrane by osmosis because the concentration of water is greater outside (the cell than inside it the vacuole) accept because of the concentration gradient provided there is no contradiction any one from (it is) elastic (it is) strong (it is fully) permeable (to water) water can pass through it do not credit semi-permeable do not credit cell membrane is semi-permeable Page 2

22 (b) (the piece of) potato shrinks loses its turg becomes flabby becomes flaccid plasmolysis occur cytoplasm pulls away from the cell wall (because) concentration of sugar because concentration of water (solution) is greater than concentration inside the cell / vacuole inside the cell / vacuole is greater than concentration (of water) outside water is drawn out of the cell [6] M24. any four from molecules / ions do not credit mineral salts move(d) through / across the cell wall / membrane against (a / the) concentration gradient by a series of chemical reactions (because) diffusion cannot occur energy (required) Page 22

23 (supplied by) respiration oxygen required f respiration (to occur) [4] M25. (i) C 6H 2O 6 + 6O 2 6CO 2 + 6H 2O energy is neutral fmulae all crect with no omissions / deletions crectly balanced credit mark if the answer is the exact reverse of an increct answer f (a) and three from take up of (soluble) substances / ions against the concentration gradient when the concentration (of the substance / ions) is greater inside the cell / cytoplasm than outside it through the (semi-permeable) (cell) membrane energy from mitochondria energy from respiration not just energy 3 [5] Page 23