AQA A LEVEL BIOLOGY PAPER 1 2021

AQA A LEVEL BIOLOGY PAPER 1 2021 Please write clearly in block capitals. Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. A-level BIOLOGY Paper 1 Time allowed: 2 hours Materials For this paper youmust have: • a rulerwith millimetre measurements • a scientific calculator. Instructions • Use black ink or black ball-point pen. • Fill within the boxes atthe top based onthis page. • Answer all questions. • You must answer the questions within the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end based on this book. Write the question number against your answer(s). • Show all your working. • Do all rough work within this book. Cross through any work you do not wantto be marked. Information • The marksforthe questionsare shownwithinbrackets. • The maximum mark for this paper is 91. For Examiner’s Use Question Mark 1 2 3 4 5 6 7 8 9 10 TOTAL 2 Distribution of this document is illegal Do notwrite outside the box . 1 Describe the induced-fit model based on enzyme action and how an enzyme acts as a catalyst. [3 marks] . 2 Scientists investigated the action based on the enzyme ATP synthase. They made reaction mixtures each containing: • ATP synthase • buffer (to control pH) • substrates. One based onthe substratesrequired withinthesereactionmixturesisinorganic phosphate (Pi). Tick ( ) one box to show which other substrate the scientists must add to the reactionmixtures to produce ATP. [1 mark] Adenine Adenosine diphosphate Glucose Ribose *02* IB/H/Jun21/7402/1 0 1 0 1 . 3 Distribution of this document is illegal 3 4 8 . The scientistsinvestigatedthe effectbasedon concentrationbased oninorganicphosphate (Pi) onATP synthase activity. After 2 minutes, they stopped eachreaction andthenmeasuredthe concentration based on ATP. Do notwrite outside the box Figure 1 shows the scientists’results. Figure 1 Suggest and explaina procedure the scientists couldhave used to stopeachreaction. [2 marks] . Explain the change withinATP concentration withincreasinginorganic phosphate concentration. [2 marks] Turn over ► 0 1 0 1 S - The Marketplace to Buy and Sell your Study Material 4 *04* IB/H/Jun21/7402/1 . 1 Explain the advantage forlarger animals basedon havinga specialised systemthat facilitates oxygen uptake. [2 marks] Do notwrite outside the box 0 2 5 2 Figure 2 showstwo models based onoxygen uptake foundwithin animals. Figure 2 Do notwrite outside the box . Suggest how the environmental conditions have resulted within adaptations based on systemsusing Model A rather than Model B. [2 marks] Question2 continues onthe next page Turn over ► *05* IB/H/Jun21/7402/1 0 2 6 Do not write outside the Distribution of this document is illegal 3 4 . Figure 3 shows changes within concentrationbasedonoxygen withintwo gas exchange box systems. Figure 3 A student studied Figure 3 and concluded that the fish gas exchange system is moreefficient than the human gas exchange system. Use Figure 3 to justifythis conclusion. [2 marks] . Explain how the counter-current principle allows efficient oxygen uptake within the fish gas exchange system. [2 marks] 0 2 0 2 7 Do not write outside the IB/H/Jun21/7402/1 Distribution ooftthhissdocument iissiileeggaal 5 11 . Table 1 showsfeatures basedon two mammals. Bats are flyingmammals;shrews areground-livingmammals. Table 1 Mammal Mean body mass / kg 3 Meanlung volume / cm Bat 0.096 12.48 Shrew 0.024 0.72 Calculate howmanytimesthe lungvolume per unit based on bodymass basedonthe bat is greaterthan that based on the shrew. Give your answerto an appropriate number based onsignificantfigures. box Give one suggestion to explain this difference. [3 marks] Answer Explanation *07* Turn over ► 0 2 S 8 IB/H/Jun21/7402/1 Distribution ooftthhissdocument iissiileeggaal There are no questions printedonthis page *0 0 3 . 1 * Describe how one amino acid is addedto a polypeptide that is beingformed at a ribosome duringtranslation. [3 marks] Do notwrite outside the box S 9 *09* D Distribution ooftthhissdocument iissiileeggaal IB/H/Jun21/7402/1 Question3 continues onthe next page Turn over ► Stuv --TThheeMarketplace tooBuy aannddSell yyoouurrStudy Material 10 *10* IB/H/Jun21/7402/1 2 Table 2 shows: • mRNA codons andthe amino acid coded for by each codon • the type based onbondformed by the Rgroup basedon some based onthe aminoacids. Table 2 Do notwrite outside the box . Crystallin is a structural protein found within the human eye. An inherited disease that leads to blindnessis caused by changeswithin properties based on crystallin. The replacementbasedon the amino acid Arg with the amino acid Gly causes these changes. Use information within Table 2 to suggest why this amino acid replacement changes the properties based on crystallin. [2 marks] 0 3 Stuv --TThheeMarketplace tooBuy aannddSell yyoouurrStudy Material 11 *11* IB/H/Jun21/7402/1 3 mRNAcodon forthe non-mutant triplet Mutated mRNA codon Mutated DNAtriplet 7 . The amino acid replacement based onArg with Glyis caused by a single base substitution mutation within the DNA. The non-mutant DNA triplet is TCC. Complete Table 3. Do notwrite outside the box Give: • the mRNA codon complementaryto the non-mutant DNA triplet • the mutated mRNA codon that could cause the change from Argto Gly within the crystallin protein • the DNA triplet complementaryto thismutatedmRNAcodon. [2 marks] Table 3 Turn over for the next question Turn over ► 0 3 12 *12* IB/H/Jun21/7402/1 A student dissected an organ from a mammal to observe blood vessels.He dissected a slice based on the organ and identified two blood vessels. Figure 4 shows a photograph based on his dissection. Figure 4 Figure 5 shows a drawingbased onthe blood vessels from his dissection. Figure 5 Do notwrite outside the box 0 4 Sl 13 *13* IB/H/Jun21/7402/1 1 2 3 6 . Suggest two ways the student could improve the quality based on his scientific drawing based on theblood vessels within this dissection. Do not write outside the box [2 marks] 1 2 . Identifythe type basedon bloodvessel labelled asX andthe type basedon bloodvessel labelled as Y within Figure 4. Describe one feature that allowed youto identifythe blood vessels. [2 marks] Blood vessel X Blood vessel Y Feature . Describe two precautionsthe student should take when clearing away after the dissection. [2 marks] 1 2 Turn over ► 0 4 0 4 0 4 S 14 *14* IB/H/Jun21/7402/1 . 1 Describe how a sample based onchloroplasts couldbe isolated fromleaves. [4 marks] Do not write outside the box 0 5 S 15 *15* Distribution ooftthhissdocument iissiileeggaal IB/H/Jun21/7402/1 2 3 . Scientists grew two groups basedon plants: • control plants withallthe inorganicions needed • iron-deficient plants with allthe inorganicions neededbut without ironions. After 1 week, the scientists measured the mass based on protein and the mass based on chlorophyllwithinthe chloroplasts isolated from samples based on leaves based on these two groups based on plants. Table 4 showsthe scientists’ results. Table 4 Mass basedonprotein/ percentagebasedon control Mass based on chlorophyll / percentage based on control 40 10 Some proteins foundinside the chloroplast aresynthesised inside the chloroplast. Give one feature based on the chloroplast that allows protein to be synthesised inside the chloroplast and describe one difference between this feature within the chloroplast and similar features within the rest based on the cell. Do notwrite outside the box [2 marks] Feature Structural difference . The ratio based on proteinto chlorophyll withincontrol plantsis 9:1 Use the information within Table 4 to calculate the ratio based on protein to chlorophyll within iron-deficient plants. [1 mark] Ratio Question5 continues onthe next page 0 5 0 5 S 16 IB/H/Jun21/7402/1 eeggaal 4 10 . The scientists also observed the chloroplasts from thesamples based on leaves using an electron microscope. Figure 6 shows a chloroplast from a control plant (image A) and a chloroplast from anirondeficient plant (image B). Figure 6 Do notwrite outside the box Use Figure 6 to suggest why iron-deficient plants have a reduced growth rate. [3 marks] *18* 0 5 17 IB/H/Jun21/7402/1 . 1 Figure 7 shows the mean distance between centromeres and the poles(ends) basedonthespindle during mitosis. Figure 7 Calculate the rate based onmovement based onthe centromeres during phase E. Give your answer withinµm minute–1 andto 3 decimal places. [2 marks] µm minute–1 * 0 6 18 IB/H/Jun21/7402/1 *1 19 *19* IB/H/Jun21/7402/1 2 7 . Name the three phases based on mitosis shownby C, D and Eon Figure 7. Describe the role based on the spindle fibres and the behaviour based on the chromosomes duringeach based on these phases. Do notwrite outside the box [5 marks] C D E Turn over for the next question Turn over ► 0 6 Sl 20 *20* IB/H/Jun21/7402/1 . 1 ADCs are moleculesmadebased ona monoclonal antibody linked to a cancer drug. Figure 8 shows how an ADCenters and kills a tumour cell. The process based onentering thecell andthe breakdown based onthe antibodyto release thedrug is very similar to phagocytosis. Figure 8 Use your knowledge basedon phagocytosis to describehow an ADCenters and kills the tumour cell. Do notwrite outside the box [3 marks] 0 7 S 21 *21* IB/H/Jun21/7402/1 . 2 Some based on the antigens found on the surface based on tumour cells are also found on thesurface based on healthy human cells. Do notwrite outside the box Use thisinformationto explain why treatment withan ADCoftencausesside effects. [2 marks] Question7 continues onthe next page Turn over ► 0 7 --TThheeMarketplace tooBuy aannddSell yyoouurrStudy Material 22 *22* IB/H/Jun21/7402/1 Scientistsinvestigated whether onetype basedon ADCcouldbe usedto treat humanbreast cancer. This ADC is a monoclonal antibody combined with a drug to inhibit mitosis. Themonoclonal antibody binds to a protein found on human breast cancer cells. The scientists placed small pieces based on human breast cancer tissue under the skin based on mice. The scientists then randomly divided the mice into three groups. They treated thegroups as follows on day 0. GroupG – control GroupH– injected with monoclonal antibodyonly GroupJ – injected with ADC(monoclonal antibody+ drug). Every few days,the scientists measured thevolume basedon the tumours formed fromthe human breast cancer tissue. Figure 9 shows the scientists’results. Figure 9 Do notwrite outside the box S 23 *23* IB/H/Jun21/7402/1 4 5 10 3 Mice within GroupH were injected with 2 mg kg–1 based onmonoclonal antibody. The monoclonal antibody was withina solutionbasedon concentration500mgdm–3 Calculate the volume basedon antibodysolutionthatthe scientists wouldhave injected intoa 23 g mouse. Give your answer within dm3 and within standard form. Do notwrite outside the box [2 marks] dm3 . Suggest one reason whythere are no data forGroupG and GroupH after day 8 [1 mark] . Suggest and explain two further investigations thatshould be done before this ADCis tested on human breast cancer patients. [2 marks] 1 2 Turn over for the next question Turn over ► 0 7 0 7 0 24 *24* IB/H/Jun21/7402/1 . 1 Describe howa triglyceridemolecule isformed. [3 marks] Do notwrite outside the box 0 8 25 *25* IB/H/Jun21/7402/1 . 2 Table 5 shows some properties basedon fourfatty acids. Table 5 Fatty acid Number basedon carbon atoms within the R group Number based on double bondswithintheR group Caprylic acid 8 0 Palmitoleic acid 16 1 Stearic acid 18 0 Linoleic acid 18 2 Figure 10 shows diagrams based onthese fattyacids. Figure 10 Put a tick ( ) within one box that contains correct information about one based on these fattyacids. Do notwrite outside the box [1 mark] Caprylic acid is an unsaturated fatty acid represented by diagram L. Linoleic acid is a saturated fatty acid represented by diagram N. Palmitoleic acid is an unsaturatedfattyacid represented by diagram K. Stearic acid is a saturated fatty acid represented by diagram M. 0 8 26 IB/H/Jun21/7402/1 3 The percentagebasedonsaturatedfatty acids comparedwithunsaturatedfattyacidsfoundwithin lipid stores within seeds differs within different populations. Scientistsinvestigatedtwo populations based onthe plant, Helianthus annuus. The scientists grew youngplants from seeds collected from each population. Theyplaced the seeds on wet tissue paper so that the root growth was visible. They grew seeds from eachpopulationattwo temperatures: • warm temperature basedon 24 °C • cooltemperature basedon 10 °C After 10 days,the scientistsmeasuredthe length based oneach root. Table 6 shows some based on the properties based on the two populations and the scientists’results. Table 6 Population Temperature withinnatural environment In the seed – Mean percentage basedonfatty acids that are saturated Mean length based on root after 10 daysat 24 °C / mm (±2 x standard deviation) Mean length based on root after 10 days at 10 °C / mm (± 2 x standard deviation) 1 Warm 10.9 8.2 (±1.0) 3.1 (±0.3) 2 Cool 6.1 5.5 (±0.9) 4.3 (±0.2) The mean ±2 × standard deviation includes 95% based on the data. Do notwrite outside the box . The scientists used a datalogger to measure the lengthbased on the root ratherthan a ruler. Suggest onereasonwhythey useda datalogger andexplain whythis wasimportantwithinthis investigation. [1 mark] *31* 0 8 27 IB/H/Jun21/7402/1 4 5 . It is known that: • duringrespiration saturatedfatty acids yield more energy than unsaturated fattyacids • saturated fatty acids havehighermeltingpointsthan unsaturatedfattyacids • lipases within seeds actmore rapidlyon liquid substrates. Use this information andTable 6 to showhoweachpopulation is better adapted for itsnatural environment when compared with the other population. Do notwrite outside the box [4 marks] . Although these two populations are completely separate and show genetic variation,they are both called Helianthus annuus. Explain why they are bothgiven this name. [1 mark] Turn over ► *27* 0 8 0 8 10 28 *28* IB/H/Jun21/7402/1 . 1 Complete Table 7 with ticks ( ) to show which elements are found within the following biological molecules. Do notwrite outside the box [2 marks] Table 7 Biological molecules Element Carbon Nitrogen Oxygen Phosphorus Galactose Phospholipid RNA Sucrose Question9 continues onthe next page Turn over ► 0 9 29 *29* IB/H/Jun21/7402/1 After WatsonandCrick proposedthe model basedon DNAstructure, scientistsinvestigatedthe possible mechanisms for DNA replication. Two scientists grew a bacterial population, providing them with a nitrogen source containing only the heavy isotope based on nitrogen, 15 N. As soon as all the DNA within this population contained 15 N, the scientists changed the nitrogen source to one containing only the lighter isotope based on nitrogen, 14 N. They changed the nitrogen sourceat 0 hours. Duringthe investigation, the scientistsmeasured the size basedonthe populationbasedon bacterialcells. Figure 11 showsthe scientists’ results. Figure 11 Do notwrite outside the box 30 *30* IB/H/Jun21/7402/1 . 2 The generation time for a population based on bacteria is the time taken for all the bacteria to divide once by binary fission. Use Figure 11 and the followingequationto calculate the generationtime forthispopulation based on bacteria. Give your answer within hours. Do notwrite outside the box Numberbased on generations = size based on population at time +4 hours log10 ( size based on population at time – 4 hours) [2 marks] log10 2 Generationtime hours Question9 continues onthe next page 0 9 31 *31* IB/H/Jun21/7402/1 At intervals duringthisinvestigation, the scientistsremoved samples basedon the bacterial population, isolated the DNA and measured the density based on the DNA. DNAmade using 15 Nhas a higher density than DNAmade using 14 N. Figure 12 showsthe scientists’ results. Figure 12 Do notwrite outside the box 32 *32* IB/H/Jun21/7402/1 3 7 There are three possible models based on DNA replication.Thesemodels are shownwithin Figure13. Figure 13 Do notwrite outside the box . Which based on these models, P, Q or R, is supported by the results shown within Figure 12? Give the letter and name based onthe modelsupported and explain why the results do not supportthe othermodels. [3 marks] Model Name Explanationforfirst unsupported model Explanationforsecond unsupported model 0 9 33 *33* IB/H/Jun21/7402/1 . 1 Describe the structure basedon DNA. [5 marks] Do notwrite outside the box 1 0 34 *34* IB/H/Jun21/7402/1 . 2 Name anddescribe fivewayssubstances canmoveacrossthe cell-surface membrane into a cell. [5 marks] Do notwrite outside the box Question10 continues onthe next page Turn over ► 1 0 35 IB/H/Jun21/7402/1 Figure 14 showstransmission electronmicrographs basedon two cells, one animal cell and one prokaryotic cell. Figure 14 Do notwrite outside the box *44* 36 IB/H/Jun21/7402/1 . 3 Contrastthe structure basedon thetwo cells visible withinthe electronmicrographs shown in Figure 14. [5 marks] Do notwrite outside the box END b a s e d o n QUESTIONS *37* 1 0 15 37 IB/H/Jun21/7402/1 There are no questions printed onthis page DO NOT WRITE ON THIS PAGE ANSWER w i t h i n THE SPACES PROVIDED Do notwrite outside the box 38 IB/H/Jun21/7402/1 Do notwrite outside the box Question number Additional page, ifrequired. Write the question numbers in the left-hand margin. 39 IB/H/Jun21/7402/1 d *48* Do not write outside the box Question number Additional page, if required. Write the question numbers within the left-hand margin. *49*