Save My Exams! The Home of Revision Cell Structure Level Subject Exam Board Topic Sub-Topic Difficulty Level Booklet Time Allowed: 59 minutes

Transcription

1 Cell Structure Mark Scheme Level GCSE (9-) Subject Biology Exam Board AQA Topic 4. Cell Biology Sub-Topic Cell Structure Difficulty Level Bronze Level Booklet Mark Scheme Time Allowed: 59 minutes Score: /59 Percentage: /00 Page

2 M.(a) (i) A (cell) wall B cytoplasm C plasmid bacterium cell has cell wall / no nucleus / no mitochondria / plasmids present accept its DNA / genetic material is not enclosed / it has no nuclear membrane it = bacterium cell accept converse for animal cell ignore flagella (iii) any one from: chloroplast ignore chlorophyll (permanent) vacuole (b) (Long tail) moves the sperm / allows the sperm to swim towards the egg allow correct reference to other named parts of the female reproductive system (Mitochondria) release energy (for movement / swimming) allow supply / produce / provide in respiration [9] Page 2

3 M2.(a) nucleus labelled correctly cell membrane labelled correctly (b) mitosis (c) electron (microscope) (d) higher magnification (e) 45 (mm) 45 / 250 or 0.8 (mm) allow ecf 80 (µm) allow 80 (µm) with no working shown for 3 marks (f) 0.2 µm [9] Page 3

4 M3.(a) (i) 25 C pathogens (b) D more / most bacteria killed accept biggest area / ring where no bacteria are growing (c) viruses live inside cells [5] Page 4

5 M4.(a) (i) C and D no mark if more than one box is ticked any one from: do not allow if other cell parts are given in a list (have) cell wall(s) (have) vacuole(s) (b) (i) A apply list principle D apply list principle (c) respiration apply list principle [5] Page 5

6 M5.(a) (i) A = nucleus B = (cell) membrane any two from: ignore shape no (cell) wall no (large / permanent) vacuole no chloroplasts / chlorophyll 2 (b) because high to low oxygen / concentration or down gradient allow more / a lot of oxygen molecules outside ignore along / across gradient (c) a tissue [6] Page 6

7 M6. any box on the left joined to > other box - cancel [4] Page 7

8 M7.(a) (i) A = (cell) membrane B = cytoplasm do not accept cytoplast To control the activities of the cell (b) extra lines cancel 3 [6] Page 8

9 M8.(a) (i) Chromosomes Characteristics (iii) Classify (b) Plants ignore algae [4] Page 9

10 M9.(a) A (inoculating / wire) loop B Petri dish allow (agar) plate ignore ref to culture medium (b) (i) to kill (unwanted) bacteria / microorganisms / microbes allow fungi ignore viruses / germs (iii) Using a flame any one from: so bacteria / microorganisms / microbes / pathogens / fungi (growing in dish) do not get out ignore reference to gases ignore viruses / germs so bacteria / microorganisms / microbes / pathogens / fungi (from the air) do not get in. ignore viruses / germs (c) 25 C [6] Page 0

11 M0.(a) A = nucleus allow phonetic spelling (b) B = (cell) membrane for repair / growth or to replace cells ignore new cells / skin (c) (i) embryos paralysis [5] Page

12 Cell Structure Mark Scheme Level GCSE (9-) Subject Biology Exam Board AQA Topic 4. Cell Biology Sub-Topic Cell Structure Difficulty Level Silver Level Booklet Mark Scheme Time Allowed: 58 minutes Score: /58 Percentage: /00 Page

13 M. (a) (i) nucleus diffusion (b) increases / larger surface area (for diffusion) ignore large surface area to volume ratio (c) (i) sugar / glucose accept amino acids / other named monosaccharides (iii) against a concentration gradient or from low to high concentration (active transport requires) energy (from) respiration (d) minerals / ions accept named ion ignore nutrients do not accept water [8] Page 2

14 M2. (a) contract / shorten ignore relax do not allow expand to churn / move / mix food accept peristalsis / mechanical digestion ignore movement unqualified (b) 400 acceptable range allow mark for answer in range of 39 to 4 allow mark for answer in range of 3900 to (c) to transfer energy for use allow to release / give / supply / provide energy do not allow to make / produce / create energy allow to make ATP ignore to store energy by (aerobic) respiration or from glucose do not allow anaerobic energy released for respiration = max mark (d) (i) to make protein / enzyme ignore antibody or other named protein too small / very small allow light microscope does not have sufficient magnification / resolution Page 3

15 allow ribosomes are smaller than mitochondria ignore not sensitive enough ignore ribosomes are transparent [8] Page 4

16 M3. (a) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the information in the Marking guidance, and apply a best-fit approach to the marking. 0 marksno relevant content. Level (-2 marks)there is a brief description of at least one of the stages (pre-inoculation, inoculation, post-inoculation). Level 2 (3-4 marks)there is a simple description of at least two stages and an explanation of at least one of them. Level 3 (5-6 marks)there is a clear description of all three stages and an explanation of at least two of them. Examples of Biology points made in the response: Pre-inoculation Petri dish and agar sterilised before use to kill unwanted bacteria inoculating loop passed through flame / sterile swab to sterilise / kill (other) bacteria Inoculation loop/swab used to spread/streak bacterium onto agar Allow other correct methods, eg bacterial lawns lid of Petri dish opened as little as possible to prevent microbes from air entering Post-inoculation sealed with tape to prevent microbes from air entering incubate Page 5

17 to allow growth of bacteria 6 (b) (i) bacteria killed / destroyed ignore fights / attacks / stops growth / got rid of Might be correct largest area / space where no bacteria are growing allow most bacteria killed Might not be correct (need more evidence as) D may be harmful to people / animals / surfaces ignore ref to cost / dangerous or harmful unqualified or may work differently with different bacteria or disinfectants may be different concentrations ignore different amounts of disinfectant unless reference to different drop size or may not last as long ignore take longer to work allow reference to anomalous result or not repeated [9] Page 6

18 M4. (a) any two from: only one chromosome allow one strand of DNA circular allow loop may have plasmids not in a nucleus / no nucleus 2 (b) (i) any one from: London is much higher or converse more variable / wider range allow on average it is 5 / 6 times greater increases Included figures must be correct (iii) overall slight increase accept doesn t change much variable / goes up and down (c) (i) both axes correctly labelled x = Year y = Number of cases correct points Page 7

19 all correct = 2 marks -2 errors = mark > 2 errors = 0 marks 2 suitable line of best fit accept straight line or smooth curve doesn t fit the pattern / line of best fit (d) provides immunity / protection (to TB) ignore stops people catching it ignore resistance prevents TB spreading accept ref to herd immunity [3] Page 8

20 M5. (a) (i) chloroplast cell wall (b) (i) osmosis accept diffusion cell wall (prevents bursting) (c) (i) carbon dioxide allow correct formula glucose allow sugar / starch any two from: light sensitive spot detects light tells flagellum to move towards light more light = more photosynthesis 2 (d) (cell has) larger SA:volume ratio short (diffusion) distance allow correct description Page 9

21 (diffusion) via cell membrane is sufficient / good enough or flow of water maintains concentration gradient [] Page 0

22 M6. (a) (i) xylem water minerals / ions / named example(s) ignore nutrients (b) (i) movement of (dissolved) sugar allow additional substances, eg amino acids / correct named sugar (allow sucrose / glucose) allow nutrients / substances / food molecules if sufficiently qualified ignore food alone sugars are made in the leaves so they need to be moved to other parts of the plant for respiration / growth / storage (c) (i) mitochondria for movement of minerals / ions Do not accept water against their concentration gradient Page

23 [9] Page 2

24 Cell Structure Mark Scheme Level GCSE (9-) Subject Biology Exam Board AQA Topic 4. Cell Biology Sub-Topic Cell Structure Difficulty Level Silver Level Booklet Mark Scheme Time Allowed: 60 minutes Score: /59 Percentage: /00 Page

25 M. (a) C (b) cytoplasm and cell membrane dividing accept cytokinesis for mark to form two identical daughter cells (c) stage 4 only one cell seen in this stage (d) (4 / 36) / (minutes) allow 0 (minutes) with no working shown for 3 marks (e) binary fission do not accept mitosis (f) shortage of nutrients / oxygen Page 2

26 so cells die or death rate = rate of cell division [] Page 3

27 M2. (a) hold cells together or prevent flow of cells or trap cells (b) 2500 if correct answer, ignore working / lack of working for mark ignore any units 2 (c) (i) size RBC approximately same size capillary or no room for more than one cell or only one can fit or RBC is too big allow use of numbers do not accept capillaries are narrow more oxygen released (to tissues) or more oxygen taken up (from lungs) and any two from: slows flow or more time available shorter distance (for exchange) or close to cells / capillary wall more surface area exposed 2 [7] Page 4

28 M3. (a) any two from: sterilise / kill microorganisms ignore cleaning / disinfect ignore germs method of sterilisation eg apparatus / media sterilised in oven / autoclave allow pressure cooker / boiling water pass flask mouth / pipette tip / loop / test tube mouth through flame work near a flame minimise opening of flask / test tube or hold non-vertical allow idea of sealing / covering or prevent entry of air 2 (b) any two from: temperature ignore references to time / type of bacterium concentration / amount of nutrients / ions type of nutrient volume / amount of solution amount of bacteria added agitation or amount of oxygen 2 (c) (i) 7.5 accept in range use more ph values around / close to ph 7.5 / between 7 and 8 [6] Page 5

29 M4. (a) A cytoplasm in this order only B (cell) membrane do not accept (cell) wall (b) (i) synapse (as) chemical accept neurotransmitter or named ignore references to how the chemical is passed do not accept electrical (c) (from light-sensitive cell to connecting neurone) to sensory neurone ignore references to synapses accept nerve cell for neuron(e) throughout penalise nerve for neurone once only (sensory neurone) to brain / CNS allow (sensory neurone) to relay neurone / spinal cord (brain / CNS) to motor neurone allow (relay neurone / spinal cord) to motor neurone (motor neurone) to (eyelid) muscle ignore effector [8] Page 6

30 M5. (a) (i) diffusion is down the concentration gradient for a description of diffusion ignore along / across gradients to enter must go up / against the concentration gradient accept by diffusion ions would leave the root or concentration higher in the root / plant or concentration lower in the soil active transport allow active uptake (b) (i) (root hairs ) large surface / area (aerobic) respiration do not allow anaerobic releases / supplies / provides / gives energy accept make ATP (for active transport) do not allow makes / produces / creates energy (iii) starch is energy source / store (for active transport) allow starch can be used in respiration do not allow makes / produces / creates energy Page 7

31 [7] M6. (a) both parents Aa accept other upper and lower case letter without key or symbols with a key allow as gametes shown in Punnett square aa in offspring correctly derived from parents or aa correctly derived from the parents given ignore other offspring / gametes for this mark parents do not have to be correct offspring aa identified as having cystic fibrosis may be the only offspring shown or 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 (more) 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 max 3 any two from: Page 8

32 ignore references to abortion 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 ignore risk unqualified ethical or religious issues linked with killing embryos accept wrong / cruel to embryos accept right to life argument ignore embryos are destroyed (high) cost of procedure possible damage to embryo (during testing for 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 or 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 do not accept movement of ions / solution by osmosis / diffusion Page 9

33 more concentrated solution outside cell / in mucus assume concentration is concentration of solute unless answer indicates otherwise or accept correct description of water concentration water moves from dilute to more concentrated solution allow correct references to movement of water in relation to concentration gradient partially permeable membrane (of cell) allow semi / selectively permeable 3 [] Page 0

34 M7. (a) (i) mitochondrion / mitochondria must be phonetically correct carbon dioxide / CO 2 water / H 2O in either order accept CO2 but not CO 2 accept H2O or HOH but not H 2 O (iii) diffusion high to low concentration allow down a concentration gradient through (cell) membrane or through cytoplasm do not accept cell wall (b) ribosomes make proteins / enzymes using amino acids part A / mitochondria provide the energy for the process allow ATP do not accept produce or make energy [9] Page

35 Cell Division Mark Scheme Level GCSE (9-) Subject Biology Exam Board AQA Topic 4. Cell Biology Sub-Topic Cell Division Difficulty Level Bronze Level Booklet Mark Scheme Time Allowed: 43 minutes Score: /43 Percentage: /00 Page

36 M.(a) nucleus labelled correctly cell membrane labelled correctly (b) mitosis (c) electron (microscope) (d) higher magnification (e) 45 (mm) 45 / 250 or 0.8 (mm) allow ecf 80 (µm) allow 80 (µm) with no working shown for 3 marks (f) 0.2 µm [9] Page 2

37 M2. (a) chromosomes (b) diagram showing four separate chromosomes two long and two short (as in diagram ) allow each chromosome shown as two joined chromatids do not allow if chromosomes touching each other (c) (i) any two from: can grow into any type of tissue / named tissue used in medical research used to treat human diseases large numbers can be grown 2 any two from: expensive grow out of control / ref cancers may be rejected need for drugs (for rest of life) 2 [6] Page 3

38 M3. (a) cell division / bacterium divides / multiplies / reproduces allow asexual / mitosis ignore growth (b) / / do not accept.8 /.8 04 /.8 4 allow ecf from wrong count (c) to kill / destroy other microorganisms / named type or to prevent contamination ignore germs / viruses to prevent other microorganisms affecting the results or other microorganisms would be counted allow to give accurate / reliable results (d) prevent growth of pathogens / disease-causing microorganisms / dangerous microorganisms do not accept microorganisms become pathogenic ignore germs / viruses ignore general safety / biohazards / harmful products produced by bacteria (e) to improve the reliability of the investigation / check for anomalies do not accept accuracy / precision / fairness / validity ignore averages / repeatability / reproducibility [7] Page 4

39 M4. (a) asexual (b) mitosis (c) genes [3] Page 5

40 M5. (a) 2 and 3 (b) cell P has an X chromosome; cell R has a Y chromosome (c) any two from: (formed from) different egg / 2 eggs (formed from) different sperm / 2 sperm have different genes / alleles / chromosomes / DNA allow genetics 2 (d) (i) stem cells the cells divide the cells differentiate (iii) (iv) (medical) research / named eg growing organs or medical / patient treatment allow (embryo) cloning do not allow designer babies / more babies any one from: ethical / moral / religious objections ignore cruel / not natural / playing God potential harm to embryo allow deformed ignore harm to mother [9] Page 6

41 M6. (a) comparisons are not required but should be credited accept a clear indication of the statement even if incomplete can develop into most other types of cell each cell divides every 30 minutes low chance of rejection by the patient s immune system (b) any three from: cheaper / only costs 000 this must be comparative ignore costs 000 can collect many (stem) cells adults give permission for their own bone marrow to be collected comparisons are not required but should be credited safe 3 [6] Page 7

42 M7. (a) A = nucleus allow phonetic spelling (b) B = (cell) membrane for repair / growth or to replace cells ignore new cells / skin (c) (i) embryos paralysis [5] Page 8

43 Cell Division Mark Scheme Level GCSE (9-) Subject Biology Exam Board AQA Topic 4. Cell Biology Sub-Topic Cell Division Difficulty Level Silver Level Booklet Mark Scheme Time Allowed: 26 minutes Score: /26 Percentage: /00 Page

44 M. (a) to kill virus or to prevent virus spreading (b) take (stem) cells from meristem or tissue culture allow take cuttings (c) use Benedict s solution glucoses turns solution blue to orange (d) Level 2 (3 4 marks): A detailed and coherent explanation is provided. The student makes logical links between clearly identified, relevant points that explain why plants with TMV have stunted growth. Level ( 2 marks): Simple statements are made, but not precisely. The logic is unclear. 0 marks: No relevant content. Indicative content less photosynthesis because of lack of chlorophyll therefore less glucose made so less energy released for growth because glucose is needed for respiration and / or therefore less amino acids / proteins / cellulose for growth because glucose is needed for making amino acids / proteins / cellulose 4 [8] Page 2

45 M2. (a) Mitosis only Meiosis only Both mitosis and meiosis How cells are replaced How gametes are made How a fertilised egg undergoes cell division How copies of the genetic information are made How genetically identical cells are produced if more than one tick per row then no mark ignore first row (b) (i) (adult) bone marrow accept (umbilical) cord blood, skin, amniotic fluid / membrane cells will not be rejected by the patient s body (if they have been produced by therapeutic cloning) allow easier to obtain linked to embryo stem cells or (embryo stem cells) can develop into many different types of cells allow doesn t need an operation linked to bone marrow or (embryo stem cells) not yet differentiated / specialised or undifferentiated accept embryo cells are pluripotent Page 3

46 [6] M3. (a) (i) mitosis correct spelling only replicates / doubles / is copied / duplicates accept cloned ignore multiplied / reproduced (b) fertilisation occurs / fusion (of gametes) accept converse for asexual, eg none in asexual / just division in asexual so leading to mixing of genetic information / genes / DNA / chromosomes genes / DNA / chromosomes / genetic information comes from parent in asexual ignore characteristics one copy (of each allele / gene / chromosome) from each parent or gametes produced by meiosis or meiosis causes variation meiosis must be spelt correctly [5] Page 4

47 M4. (a) circles round right hand X and Y gametes put two ticks or crosses by the circles 2 (b) 50:50 or : or 50% or 0.5 or ½ equal or evens credit even do not accept 2: or 50 / 50 (c) (i) credit the same as the one above to be marked consequential (d) DNA do not accept nucleic acid (e) same [7] Page 5

48 Cell Division Mark Scheme Level GCSE (9-) Subject Biology Exam Board AQA Topic 4. Cell Biology Sub-Topic Cell Division Difficulty Level Gold Level Booklet Mark Scheme Time Allowed: 59 minutes Score: /58 Percentage: /00 Page

49 M. (a) C (b) cytoplasm and cell membrane dividing accept cytokinesis for mark to form two identical daughter cells (c) stage 4 only one cell seen in this stage (d) (4 / 36) / (minutes) allow 0 (minutes) with no working shown for 3 marks (e) binary fission do not accept mitosis Page 2

50 (f) shortage of nutrients / oxygen so cells die or death rate = rate of cell division [] Page 3

51 M2. (a) A = meiosis accept mieosis do not accept miosis B = mitosis do not accept meitosis etc (b) fertilisation allow conception (c) (i) [5] Page 4

52 M3. any four from: cells used to treat diseases do not go on to produce a baby produces identical cells for research cells would not be rejected allow cells can form different types of cells (immature) egg contains only genetic information / DNA / genes / chromosomes from mother or there is only one parent asexual / no mixing of genetic material / no sperm involved / no fertilisation or chemical causes development baby is a clone reference to ethical / moral / religious issues allow ethically wrong NB cloning is illegal gains 2 marks ignore unnatural risk of damage to the baby in correct context [4] Page 5

53 M4. one mark for each of the following comparisons to a maximum of 6 candidates must make a clear comparison meiosis sexual gametes ovary or testes or gonads half number of chromsomes mitosis asexual growth all other cells same number of chromosomes haploid or diploid or 23 chromosomes 46 chromosomes reassortment or variation possible or not identical no reassortment or no variation or identical 4 cells produced 2 cells produced 2 divisions division [6] Page 6

54 M5. (a) any one from chromosomes in pairs inherited one of each pair from each parent one of each pair in egg and one of each pair in sperm so sex cells / gametes can have half the number allow need to pair during cell division / meiosis (b) any two from: code combination / sequence of amino acids forming specific / particular proteins / examples If no other mark gained allow reference to controlling characteristics / appearance for mark 2 (c) (i) C 30 (d) (i) for growth / repair / replacement / asexual reproduction do not accept incorrect qualification, eg growth of cells or repair of cells they equals cells therefore do not accept they grow etc 44 or 22 pairs [7] Page 7

55 M6. Marks should not be awarded for simply copying the information provided A mark may be awarded for a comparison between treatments if the answer only involves copied information any four from: For all 4 marks to be awarded, there must be at least pro and con embryo stem cells examples of pros can treat a wide variety / lots of diseases / problems many available / plentiful using them better than wasting them painless cons (possible) harm / death to embryo (relatively) untested / unreliable / may not work allow long term effects not known or may be more risky embryo can t be asked / embryo rights idea adult bone marrow stem cells examples of pros no ethical issues (in collection) or permission given quick recovery (relatively) safe allow does not kill (donor) / low risk well tried / tested / know they work cons operation hazards eg infection few types of cell / tissue produced or few diseases / problems treated painful so may deter donors 4 Page 8

56 Conclusion to evaluation: A reasoned conclusion from the evidence [5] Page 9

57 M7. (a) (i) DNA replication / copies of genetic material were made it = a chromosome allow chromosomes replicate / duplicate / are copied ignore chromosomes divide / split / double one copy of each (chromosome / chromatid / strand) to each offspring cell ignore ref. to gametes and fertilisation each offspring cell receives a complete set of / the same genetic material allow so offspring (cells) are identical (b) (i) meiosis allow mieosis as the only alternative spelling Species A = 4 and Species B = 8 (iii) sum of A + B from (b) e.g. 2 (c) (i) similarities between chromosomesorsimilarities between flowers described e.g. shape of petals / pattern on petals / colour / stamens can breed / can sexually reproduce allow can reproduce with each other / they can produce offspring Page 0

58 any two from: offspring contain 3 copies of each gene / of each chromosome / odd number of each of the chromosomes some chromosomes unable to pair (in meiosis) (viable) gametes not formed / some gametes with extra / too many genes / chromosomes orsome gametes with missing genes / chromosomes 2 [0] Page

59 M8. (a) (i) allele expressed even when other allele present or expressed if just one copy of allele is present or expressed if heterozygous if present other allele not expressed 2 affected parents have unaffected child or and 2 5 / 6 or if recessive all of and 2 s children would have CADASIL (iii) heterozygous has unaffected children or because if homozygous all children would have CADASIL (b) genetic diagram including: accept alternative symbols, if defined correct gametes: D and d and d (and d) ignore 7 / 8 or male / female derivation of offspring genotypes: Dd Dd dd dd allow just Dd dd if ½-diagram allow ecf if correct for student s gametes identification of Dd as CADASILor dd as unaffected allow ecf if correct for student s gametes correct probability: 0.5 / ½ / in 2 / 50% / : Page 2

60 (c) (i) stem cells can differentiate or are undifferentiated / unspecialised can form blood vessel cells / brain cells or stem cells can divide ethical argument - eg no risk of damage to embryo or adult can give consent for removal of cells or adult can re-grow skin more ethical qualified ignore religion unqualified orif from a relative then less chance of rejection or if from self then no chance of rejectionorskin cells more accessible [0] Page 3

61 Transport in Cells Mark Scheme Level GCSE (9-) Subject Biology Exam Board AQA Topic 4. Cell Biology Sub-Topic Transport in Cells Difficulty Level Bronze Level Booklet Mark Scheme Time Allowed: 65 minutes Score: /54 Percentage: /00 Page

62 M.(a) (i) diffusion apply list principle A apply list principle (b) (i) osmosis apply list principle R apply list principle [4] Page 2

63 M2. (a) (i) capillary diffusion (iii) Carbon dioxide low(er) high(er) Oxygen high(er) low(er) mark for each correct row (b) (i) red blood cells haemoglobin [6] Page 4

64 M3.(a) xylem and phloem either order allow words ringed in box allow mis-spelling if unambiguous (b) (i) movement / spreading out of particles / molecules / ions / atoms ignore names of substances / gases from high to low concentration accept down concentration gradient ignore along / across gradient ignore with gradient oxygen / water (vapour) allow O 2 / O2 ignore O 2 / O allow H 2O / H2O ignore H 2 O [4] Page 5

65 M4.(a) 300 (b) suitable scale on y-axis label y-axis 4 bars drawn correctly allow mark for 3 correct bars 2 (c) increases from 50 to 500 then decreases from 500 to 0 (d) carbohydrates broken down / digested into sugars broken down by carbohydrase or amylase (e) absorption of glucose into blood Page 6

66 by active transport allow diffusion [2] Page 7

67 M5.(a) (i) A = nucleus B = (cell) membrane any two from: ignore shape no (cell) wall no (large / permanent) vacuole no chloroplasts / chlorophyll 2 (b) because high to low oxygen / concentration or down gradient allow more / a lot of oxygen molecules outside ignore along / across gradient (c) a tissue [6] Page 8

68 M6.(a) osmosis partially permeable (b) (i) any two from: allow correct answers in terms of A vacuole is small(er) cytoplasm has shrunk allow cytoplasm is smaller gap between cytoplasm and cell wall cell wall curves inwards allow cell B is flaccid or cell A is turgid the (cell) membrane has moved away from the wall 2 any one from: water will move / diffuse in (cells) will swell (cells) will burst ignore turgid (c) villi give the small intestines a large surface area villi have many blood capillaries [7] Page 9

69 M7.(a) (i) water / H 2O accept oxygen allow H 2O do not allow H 2 O or H2O (iii) the mineral ions are absorbed by active transport the absorption of mineral ions needs energy have (many root) hairs (which) give a large surface area (for absorption) (b) carbon dioxide in or oxygen out or control water loss accept gas exchange ignore gases in and out ignore gain / lose water (c) (i) guard cells (stomata are) closed allow there is no gap / space (iii) plant will wilt / droop ignore die [9] Page 0

70 M8.(a) (i) alveoli / alveolus allow air sacs allow phonetic spelling any one from: protection (of lungs / heart) help you breathe / inflate lungs. (b) (i) diffusion capillaries (iii) any two from: (have many) alveoli allow air sacs large surface / area thin (exchange) surface or short diffusion pathway accept only one / two cell(s) thick good blood supply / many capillaries allow (kept) ventilated or maintained concentration gradient. 2 [6] Page

71 Transport in Cells Mark Scheme Level GCSE (9-) Subject Biology Exam Board AQA Topic 4. Cell Biology Sub-Topic Transport in cells Difficulty Level Silver Level Booklet Mark Scheme Time Allowed: 58 minutes Score: /58 Percentage: /00 Page

72 M. (a) (i) variation in masses / more representative / more typical / more reliable / average / mean / reference to anomalies or one worm to light to measure change do not allow more accurate / more precise ignore fair test / valid / repeatable / reproducible remove solution / liquid (on outside of worm) allow water (iii) variable amounts removed from each worm ignore reference to length of timing (iv) equal sizes of worm / more worms (in each group) / wash off all the sand / repeats / use more accurate balance / use smaller concentration intervals allow reference to improve blotting technique eg blot before / blot more thoroughly (b) (i) different (starting) masses / sizes / weights (at different concentrations) allows comparisons / shows pattern / shows trend (+)20 correct answer = 2 marks, with or without working Page 2

73 or for mark 2 (c) (i) graph: points correct allow ± mm mark per error allow ecf from part b 2 label on x-axis including units ie Concentration of salt in arbitrary units line of best fit = smooth curve / ruled straight line anomaly (4.0, 52) either plotted and ignored re. line or not plotted do not allow point to point allow best fit for ecf from 2bii on graph: ring drawn around point at (4.0, 52) allow (5.0, 50) if cand. line indicates this (iii) sensible suggestion eg used wrong solution / used 5.0% instead of 4.0% / different length of time in solutions / ref to error in blotting / balance not zeroed / error in weighing allow some lugworms died allow error in calculation Page 3

74 (d) (i) 2.9 to 3.0 / correct for candidate s graph ± 0. value of no change in mass / worms in equilibrium with soln / described allow small(est) mass change water loss by osmosis / diffusion from dilute region in the worm to more concentrated solution outside allow correct description in terms of high to low water concentration / high to low water potential salt solution is hypertonic concentration unqualified = salt concentration [9] Page 4

75 M2. (a) active transport (b) by transpiration stream / pull in xylem (c) any three in the correct order from: mount epidermis on a slide count stomata in one area repeat in four more areas repeat method on other surface of leaf calculate mean allow nail varnish film 3 (d) allow numbers written out in a line with middle number circled (e) ( ) / 5 = allow 4 with no working shown for 2 marks allow 4.2 for mark (f) less water lost so it does not wilt Page 5

76 [] M3.(a) (i) xylem water minerals / ions / named example(s) ignore nutrients (b) (i) movement of (dissolved) sugar allow additional substances, eg amino acids / correct named sugar (allow sucrose / glucose) allow nutrients / substances / food molecules if sufficiently qualified ignore food alone sugars are made in the leaves so they need to be moved to other parts of the plant for respiration / growth / storage (c) (i) mitochondria for movement of minerals / ions Do not accept water Page 6

77 against their concentration gradient [9] Page 7

78 M4. (a) (i) chloroplast cell wall (b) (i) osmosis accept diffusion cell wall (prevents bursting) (c) (i) carbon dioxide allow correct formula glucose allow sugar / starch any two from: light sensitive spot detects light tells flagellum to move towards light more light = more photosynthesis 2 (d) (cell has) larger SA:volume ratio short (diffusion) distance allow correct description Page 8

79 (diffusion) via cell membrane is sufficient / good enough or flow of water maintains concentration gradient [] M5. (a) (i) nucleus diffusion (b) increases / larger surface area (for diffusion) ignore large surface area to volume ratio (c) (i) sugar / glucose accept amino acids / other named monosaccharides (iii) against a concentration gradient or from low to high concentration (active transport requires) energy (from) respiration (d) minerals / ions accept named ion ignore nutrients do not accept water [8] Page 9

80 Page 0

81 Transport in Cells Mark Scheme Level GCSE (9-) Subject Biology Exam Board AQA Topic 4. Cell Biology Sub-Topic Transport in Cells Difficulty Level Gold Level Booklet Mark Scheme Time Allowed: 58 minutes Score: /57 Percentage: /00 Page

82 M. (a) glucose is absorbed by diffusion into the bloodstream then blood delivers glucose to muscles in capillaries (b) to stop air getting in (c) yellow (d) collect the CO 2 / gas with a measuring cylinder / gas syringe (volume collected) in a certain time using a timer / watch (e) yeast produces ethanol but muscles produce lactic acid marks can be awarded from correct word or balanced symbol equations yeast produces CO 2 but muscles do not answers must be comparative both release small amounts of energy Page 2

83 ignore both occur without oxygen [9] Page 3

84 M2. (a) (i) mitochondrion / mitochondria must be phonetically correct carbon dioxide / CO 2 water / H 2O in either order accept CO2 but not CO 2 accept H2O or HOH but not H 2 O (iii) diffusion high to low concentration allow down a concentration gradient through (cell) membrane or through cytoplasm do not accept cell wall (b) ribosomes make proteins / enzymes using amino acids part A / mitochondria provide the energy for the process allow ATP do not accept produce or make energy [9] Page 4

85 M3.(a) motor allow efferent / postsynaptic allow another relay (neurone) (b) release of chemical (from relay neurone) allow ecf for motor neurone from (a) allow release of neurotransmitter / named example chemical crosses gap / junction / synapse allow diffuses across allow chemical moves to X chemical attaches to X / motor / next neurone (causing impulse) (c) (curare) decrease / no contraction accept (muscle) relaxes (strychnine) increase / more contraction if no other mark awarded allow mark for (curare) decrease / no response and (strychnine) increase / more response [6] Page 5

86 M4.(a) more concentrated must be a comparison than the cell / cytoplasm accept more salty / solutes / ions accept cell is less concentrated than solution for 2 marks (b) (i) turgid plasmolysed accept flaccid (c) any four from: water left the cells (in A) by osmosis from dilute to more concentrated solution accept high to low water potential or from high to low water concentration via partially permeable membrane so cell membrane shrank away from cell wall 4 (d) water enters the cells (by osmosis) allow mark for: they burst / lyse / lysis occurs water leaves and cell shrinks (if they think it is hypertonic solution) animal cells have no cell wall or plant cells have a cell wall cell wall prevents lysis / bursting / allows turgidity allow correct description [2] Page 6

87 M5.(a) (i) diaphragm accept phonetic spelling (because) the volume (inside the jar) increases maximum two marks if no reference to correct 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 or active transport from a high concentration (of oxygen) to a low concentration allow down its / oxygen concentration gradient from the air or to the blood or (because) there is a high(er) concentration (of oxygen) in the air or there is a low(er) concentration of oxygen in the blood ignore reference to amount of oxygen many gill filaments must be in the correct pairs to gain 2 marks (give a) large surface / area do not allow surface area to volume ratio or thin (so) short diffusion pathway or good blood supply (to) maintain the concentration gradient or water continually flows over them / continually ventilated (to) maintain the concentration gradient [8] Page 7

88 M6. (a) (0.5 /.35) 00. (%) allow. (%) with no working shown for 2 marks (b) to allow results to be compared or they had different masses at the start (c) axis correct scale and labelled 5 points correctly plotted allow ecf from 05. allow mark for 4 points correctly plotted 2 line of best fit (d) 0.5 allow (e) (0.0 to 0.4) water moves into cells (0.6 to 0.8) water leaves cells Page 8

89 by osmosis (f) any two from: concentration of solutions drying of chips accuracy of balance evaporation from tubes 2 [3] Page 9