2024_AQA: AS BIOLOGY Paper 1 (Merged Question paper and marking scheme) Monday 13 May 2024

2024_AQA: AS BIOLOGY Paper 1 (Merged Question paper and marking scheme) Monday 13 May 2024 Please write clearly in block capitals. Centre number Surname Forename(s) Candidate number Candidate signat ure AS BIOLOGY Paper 1 I declare this is my own work. Monday 13 May 2024 Materials For this paper you must have: Morning  a ruler with millimetre measurements  a scientific calculator. Instructions  Use black ink or black ball-point pen.  Fill in the boxes at the top of this page.  Answer all questions. Time allowed: 1 hour 30 minutes For Examiner’s Use Question Mark 1 2 3 4 5  You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. 6  If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s).  Show all your working.  Do all rough work in this book. Cross through any work you do not want to be marked. Information  The marks for the questions are shown in brackets.  The maximum mark for this paper is 75. 7 8 9 TOTAL AS Biology Paper 1: Key Areas to Revise This paper focuses on core biological principles, testing your understanding of key concepts in biology. The main areas to revise are: 1. Cell Structure and Function: Understand the structure and function of different organelles in both prokaryotic and eukaryotic cells. Be able to explain processes like protein synthesis, cell division (mitosis and meiosis), and cell transport mechanisms (e.g., osmosis, active transport). 2. Biological Molecules: Revise the structure and function of macromolecules, including carbohydrates, lipids, proteins, and nucleic acids. Know their roles in living organisms and how they contribute to processes like energy transfer, enzyme activity, and DNA replication. 3. Enzyme Action: Understand how enzymes work, including the lock and key model, enzyme-substrate specificity, factors affecting enzyme activity (temperature, pH, concentration), and the role of enzymes in metabolic pathways. 4. Exchange and Transport: Focus on the structure and function of the circulatory system, including blood, heart, and blood vessels. Understand the processes of gas exchange in plants and animals, including the adaptations of respiratory surfaces. 5. Genetics and Inheritance: Revise the basics of DNA structure, gene expression, and inheritance patterns. Understand concepts such as Mendelian genetics, monohybrid crosses, codominance, and sex linked inheritance. 6. Ecology: Be familiar with ecological concepts like energy flow, food chains, food webs, and the role of biodiversity in ecosystems. Know how environmental factors can influence species distribution. By revising these topics thoroughly, you'll be prepared for the wide range of questions that could appear on AS Biology Paper 1. IB/M/Jun24/G4001/E9 7401/1 2 Do not write outside the IB/M/Jun24/7401/1 Answer all questions in the spaces provided. box 0 1 . 1 Figure 1 shows a diagram of the human gas exchange system. Figure 1 Structure B is muscle. The volume of the thorax is increased when structure B contracts. Name the structures labelled A and B. [2 marks] A B 3 Do not write outside the IB/M/Jun24/7401/1 2 . Figure 2 is a diagram of an alveolus and a blood vessel associated with the alveolus. The direction of the movement of substances is shown by the arrows labelled C, D, E, F and G. Figure 2 Complete Table 1 by writing the correct letter, C, D, E, F or G, in the box next to each statement. You may use each letter once, more than once or not at all. box [2 marks] Table 1 Box Statement represents the diffusion of oxygen represents the transport of a gas mixture represents blood moving at the highest pressure Turn over ► 1 0 4 Do not write outside the IB/M/Jun24/7401/1 [2 marks] box 6 0 1 . 3 Describe and explain one adaptation of a single alveolus for gas exchange. 5 Do not write outside the IB/M/Jun24/7401/1 1 . Table 2 contains information on the digestion of two biological molecules. Complete Table 2. [4 marks] box Table 2 Biological molecule Enzyme Name of bond hydrolysed Product of digestion Starch Maltose Dipeptide Dipeptidase A student investigated starch digestion by mixing starch with a solution of the enzyme used to digest starch. The student did a biochemical test for protein when starch digestion was completed. 0 2 . 2 Describe a biochemical test to show the presence of protein. [2 marks] Question 2 continues on the next page Turn over ► 2 0 6 Do not write outside the box IB/M/Jun24/7401/1 Answer μmol dm–3 s–1 10 0 2 . 3 The student’s test for protein was positive. Explain why. [2 marks] 0 2 . 4 An enzyme’s turnover number (kcat) is the number of substrate molecules converted into product molecules by one enzyme molecule in 1 second. It is determined using this equation. kcat = Maximum rate of enzyme-controlled reaction / μmol dm–3 s–1 Enzyme concentration / μmol dm–3 A scientist investigated the action of a protease enzyme. The scientist prepared a reaction mixture with a protease concentration of 0.0118 µmol dm–3. The kcat for the protease is 110 substrate molecules per second. Use this information and the formula to calculate the maximum rate of the protease-controlled reaction. Give your answer to 3 significant figures. Show your working. [2 marks] 7 Do not write outside the box IB/M/Jun24/7401/1 [4 marks] Question 3 continues on the next page Turn over ► 0 3 . 1 Describe how viruses are replicated. 8 Do not write outside the box IB/M/Jun24/7401/1 0 3 . 2 A scientist investigated the effect of a virus species on a bacterial culture. The scientist:  mixed a diluted sample of the virus with a bacterial culture in liquid agar  poured the liquid agar into a Petri dish and let the agar set  incubated the virus-bacterial culture at 30 °C for 24 hours. Figure 3 shows the appearance of the Petri dish after 24 hours. Figure 3 Explain why clear zones are present in Figure 3. [1 mark] 0 3 . 3 Predict the appearance of the Petri dish if the incubation was extended by a few more hours. [1 mark] 9 Do not write outside the box IB/M/Jun24/7401/1 0 3 . 4 Animal cells replicate during the cell cycle. Figure 4 shows one animal cell at a stage of the cell cycle. Figure 4 Identify the stage of the cell cycle shown in Figure 4. Explain the appearance of the cell shown in Figure 4. Do not refer to organelles in your answer. [2 marks] Identity of stage Explanation Turn over for the next question Turn over ► 8 10 Do not write outside the IB/M/Jun24/7401/1 1 . Complete Table 3 to show whether the feature of DNA is associated with the DNA molecule found in each of these locations. box Tick () the appropriate boxes. [3 marks] Table 3 Feature of DNA Location of DNA molecule Prokaryotic cell Nucleus Chloroplast Is circular Contains four different types of nucleotide Is associated with histones 4 0 11 Do not write outside the IB/M/Jun24/7401/1 Question 4 continues on the next page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED box Turn over ► 12 Do not write outside the box Some strains of the bacterium, Escherichia coli, are known to be resistant to IB/M/Jun24/7401/1 antibiotics. Scientists analysed data recording the deaths of people in hospitals across the world during 2019. They used the data to find how many of the bodies of people who died in hospitals contained antibiotic-resistant E. coli bacteria and whether the E. coli were:  not the cause of death (associated E. coli)  the cause of death (causal E. coli). Figure 5 shows their results. Figure 5 13 Do not write outside the box IB/M/Jun24/7401/1 0 4 . 2 Using Figure 5, a student calculated that out of all the people who died when antibiotic-resistant E. coli were present, 25% of those deaths involved causal E. coli. The student’s calculation is incorrect. Use Figure 5 to calculate the correct percentage of deaths involving causal E. coli in people who died when infected with antibiotic-resistant E. coli. Identify the mathematical step the student performed incorrectly in their calculation. [3 marks] Correct answer % Incorrect mathematical step 0 4 . 3 Which method is most likely to be successful in decreasing the frequency of antibiotic-resistant bacteria in populations of people? Tick () one box. [1 mark] Give people lower doses of antibiotics to treat disease. Test more people to determine if they are infected with antibiotic-resistant bacteria. Vaccinate more people to reach herd immunity against bacteria that cause diseases common in human populations. Turn over ► 7 14 Do not write outside the box IB/M/Jun24/7401/1 0 5 . 1 Malva sylvestris is a plant species. A student wanted to determine the mean height of M. sylvestris plants growing in a field. Describe how the student should obtain measurements of the plants and then process these measurements to obtain a reliable mean height of plants growing in that field. [5 marks] 15 Do not write outside the box IB/M/Jun24/7401/1 0 5 . 2 The student wanted to present the results for the distribution of plant heights in a histogram. Figure 6 shows the outline of a results table. Use Figure 6 to design a suitable results table the student should use for a histogram of plant height measurements ranging between 60 cm and 120 cm. [2 marks] Figure 6 Question 5 continues on the next page Turn over ► 16 Do not write outside the IB/M/Jun24/7401/1 3 . A student investigated biodiversity in a community of bee species in a field of wild flowers. The student trapped and identified the bee species in the field over 6 months. Table 4 shows some of the student’s results. Table 4 Bee species Total number of trapped bees after 6 months Cuckoo bee 250 Domestic honeybee 800 Clover bee 200 The index of diversity in a community of organisms is determined using the formula where N = total number of organisms of all species and n = total number of organisms of each species. Use the formula and information in Table 4 to calculate the index of diversity in this community of bee species. box [2 marks] Answer 5 0 17 Do not write outside the box IB/M/Jun24/7401/1 0 5 . 4 In a different investigation, the student found that:  the species richness of plants in a field of wild flowers is greater than the species richness of plants in a field of wheat  the species richness of bees in a field of wild flowers is greater than the species richness of bees in a field of wheat. Suggest one reason why the species richness of bees in a field of wild flowers is greater than the species richness of bees in a field of wheat. Explain your answer. [2 marks] Turn over for the next question Turn over ► 11 18 Do not write outside the box IB/M/Jun24/7401/1 0 6 . 1 Give two roles of phosphate ions in cells. [2 marks] 1 2 0 6 . 2 Diseased lungs can cause carbon dioxide to build up in the blood plasma. This leads to an increase in hydrogen ion concentration in the plasma. Describe the effect this increase in hydrogen ion concentration has on the plasma and on the proteins in the plasma. Do not refer to the Bohr effect. [2 marks] 19 Do not write outside the IB/M/Jun24/7401/1 3 Scientists measured the concentration of inorganic ions in the cytoplasm of mammalian cells and in the tissue fluid surrounding those cells. Figure 7 shows their results. Figure 7 box . Use Figure 7 to describe two patterns shown in the total concentrations of positively and negatively charged ions in the cytoplasm and in tissue fluid. [2 marks] 1 2 Turn over ► 6 0 20 Do not write outside the box IB/M/Jun24/7401/1 0 6 . 4 In these mammalian cells, the:  cell-surface membrane is permeable to sodium ions  sodium ion concentration does not increase in the cytoplasm over time. Use this information and Figure 7 to suggest and explain the ion transport mechanisms involved in the transport of sodium ions. [2 marks] 8 21 Do not write outside the box IB/M/Jun24/7401/1 0 7 . 1 A drug is delivered to diseased body cells by a monoclonal antibody. The monoclonal antibody is attached to a drug to form an antibody–drug complex (ADC). Figure 8 Complete Figure 8 to show a monoclonal antibody attached to the drug. Label one structural feature of the monoclonal antibody in your drawing of the ADC. [2 marks] Question 7 continues on the next page Turn over ► 22 Do not write outside the box IB/M/Jun24/7401/1 0 7 . 2 Scientists used a clinical trial to test an ADC designed to treat people diagnosed with the cancer, Hodgkin lymphoma (HL). In the clinical trial, the patients with HL:  were selected at random  had tumours of a similar size at the start of the trial  received identical doses of the ADC. Figure 9 shows some of the results from the clinical trial. Figure 9 Use all the information to evaluate the effectiveness of the ADC in treating people with HL. Do not refer to statistical tests in your answer. [4 marks] 6 23 Do not write outside the box IB/M/Jun24/7401/1 0 8 . 1 A non-competitive inhibitor decreases the rate of an enzyme-controlled reaction. Explain how. [3 marks] 0 8 . 2 A scientist investigated the hydrolysis of the protein casein. The scientist:  mixed a solution of a protease enzyme with a solution of casein  then measured the casein concentration in the mixture at intervals  controlled all relevant variables appropriately. For this investigation, identify: [2 marks] the independent variable the dependent variable Turn over ► 24 Do not write outside the box IB/M/Jun24/7401/1 0 8 . 4 The scientist repeated the investigation but increased the temperature to the optimum temperature for this protease. Sketch a line on Figure 10 showing the results you predict if the investigation is repeated at the optimum temperature for the protease. [2 marks] 9 0 8 . 3 Figure 10 shows the scientist’s results. Figure 10 Use Figure 10 to determine the rate of casein hydrolysis at 2 minutes. Show how you obtained your answer. [2 marks] Answer mg dm–3 minute–1 25 Do not write outside the box Turn over for the next question IB/M/Jun24/7401/1 DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Turn over ► 26 Do not write outside the box IB/M/Jun24/7401/1 0 9 Read the following passage. DNA is a stable molecule but, even under normal cell conditions, spontaneous changes occur to the DNA nucleotide sequence. One example of a spontaneous change occurs when a cytosine base in a guanine–cytosine nucleotide pair is changed to a uracil base. This produces a guanine–uracil nucleotide pair in the DNA molecule. Scientists estimate this type of spontaneous change occurs to 100 guanine–cytosine nucleotide pairs in the genome of healthy human cells every day. In healthy cells, enzyme-controlled processes repair these spontaneous changes in the DNA molecule by changing uracil bases back to cytosine bases. If these repairs do not happen, the uracil DNA nucleotide attracts an adenine DNA nucleotide when the DNA is replicated in the cell cycle. A mutation of the original DNA has now occurred. Healthy cells with damaged DNA produce enzyme X. This enzyme slows the cell cycle by delaying the start of DNA replication. People with the disease ataxia telangiectasia (AT) do not produce functional enzyme X. Mutations occur at a higher rate in people with AT. Use the information in the passage and your own knowledge to answer the following questions. 5 10 15 0 9 . 1 Give one similarity in structure between a guanine–cytosine nucleotide pair and a guanine–uracil nucleotide pair in a DNA molecule (lines 3–5). Do not refer to guanine in your answer. [1 mark] 27 Do not write outside the box IB/M/Jun24/7401/1 0 9 . 2 The DNA in a human genome contained 3 × 109 nucleotide pairs. Assume 40% of these nucleotide pairs are guanine–cytosine nucleotide pairs. Use this information and lines 5–7 to calculate the percentage of guanine–cytosine nucleotide pairs that change to guanine–uracil nucleotide pairs in this genome every day. Give your answer in standard form. Show your working. [2 marks] Answer % 0 9 . 3 The type of mutation that occurs when ‘repairs do not happen’ (lines 10–11) may still produce a functional protein. Suggest and explain why. [4 marks] Turn over ► 28 Do not write outside the box IB/M/Jun24/7401/1 0 9 . 4 Suggest and explain why ‘mutations occur at a higher rate’ in people with AT (lines 15–16). [3 marks] END OF QUESTIONS 10 29 Do not write outside the box There are no questions printed on this page IB/M/Jun24/7401/1 DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED 30 Additional page, if required. Write the question numbers in the left-hand margin. Question number IB/M/Jun24/7401/1 Do not write outside the box 31 Additional page, if required. Write the question numbers in the left-hand margin. Question number IB/M/Jun24/7401/1 Do not write outside the box 32 Do not write outside the box IB/M/Jun24/7401/1 Question number Additional page, if required. Write the question numbers in the left-hand margin. Copyright information For confidentiality purposes, all acknowledgements of third-party copyright material are published in a separate booklet. This booklet is published after each live examination series and is available for free download from Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright-holders may have been unsuccessful and AQA will be happy to rectify any omissions of acknowledgements. If you have any queries please contact the Copyright Team. Copyright © 2024 AQA and its licensors. All rights reserved. AS BIOLOGY 7401/1 Paper 1 Mark scheme June 2024 Version: 1.0 Final MARK SCHEME – AS BIOLOGY – 7401/1 – JUNE 2024 Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation events which all associates participate in and is the scheme which was used by them in this examination. The standardisation process ensures that the mark scheme covers the students’ responses to questions and that every associate understands and applies it in the same correct way. As preparation for standardisation each associate analyses a number of students’ scripts. Alternative answers not already covered by the mark scheme are discussed and legislated for. If, after the standardisation process, associates encounter unusual answers which have not been raised they are required to refer these to the Lead Examiner. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of students’ reactions to a particular paper. Assumptions about future mark schemes on the basis of one year’s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. No student should be disadvantaged on the basis of their gender identity and/or how they refer to the gender identity of others in their exam responses. A consistent use of ‘they/them’ as a singular and pronouns beyond ‘she/her’ or ‘he/him’ will be credited in exam responses in line with existing mark scheme criteria. Further copies of this mark scheme are available from Copyright information AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this booklet for their own internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any material that is acknowledged to a third party even for internal use within the centre. Copyright © 2024 AQA and its licensors. All rights reserved. 2 MARK SCHEME – AS B