Please write clearly in block capitals. Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. Time allowed: 2 hours Materials For this paper you... must have: • 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. • You must answer the questions in 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 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 91. A-level BIOLOGY Paper 1 2 *02* IB/M/Jun22/7402/1 Do not write outside the There are no questions printed on this page box DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED 3 *03* Turn over ► IB/M/Jun22/7402/1 Do not write outside the Answer all questions in the spaces provided. box 0 1 . 1 Describe the structure and function of the nucleus. [4 marks] Question 1 continues on the next page 4 *04* IB/M/Jun22/7402/1 Do not write outside the box 0 1 . 2 Name the main polymer that forms the following cell walls. [1 mark] Plant cell wall Fungal cell wall Scientists investigated the effect of the number of fungal species in soil on the diversity of plant species. Table 1 shows their raw data for soil containing 14 fungal species. Table 1 Plant species Total shoot biomass / g m–2 Poa compressa 2 Achillea millefolium 4 Aster cordifolius 5 Aster novae-angliae 7 Chrysanthemum leucanthemum 15 Daucus carota 36 Fragaria virginiana 51 0 1 . 3 Suggest one reason the scientists used biomass instead of the number of individuals of each plant species when collecting data to measure diversity. [1 mark] 5 *05* Turn over ► IB/M/Jun22/7402/1 Do not write outside the box 0 1 . 4 The scientists used this equation to calculate the plant species index of diversity. ?? = 1 −�� ?? ??� 2 where n = shoot biomass of each plant species and N = total shoot biomass of all plant species Use this equation to calculate the index of diversity for the data in Table 1. [2 marks] Index of diversity Question 1 continues on the next page 6 *06* IB/M/Jun22/7402/1 Do not write outside the box Figure 1 shows the plant species index of diversity the scientists calculated when the soil contained 0, 1, 2, 4 and 8 fungal species. Figure 1 0 1 . 5 Sometimes farmers stop growing crops on an area of land to allow the natural ecosystem to recover. The plant species index of diversity of these areas previously used to grow crops is different from nearby land that has never been used to grow crops. Suggest and explain how the plant species index of diversity would be different in these areas previously used to grow crops. Use Figure 1 and your knowledge of the effect of farming on biodiversity in your answer. [2 marks] 10 7 *07* Turn over ► IB/M/Jun22/7402/1 Do not write outside the box 0 2 . 1 Clostridium difficile is a bacterial species that causes disease in humans. Antibiotic-resistant strains of C. difficile have become a common cause of infection acquired when in hospital. Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria becoming a common cause of infection acquired when in hospital. [3 marks] 0 2 . 2 Scientists suggested that factors, other than antibiotic use, led to the increase in antibiotic-resistant C. difficile infections. One suggested factor is people eating more trehalose in their diet. Trehalose is a disaccharide formed from two glucose molecules. Name another disaccharide formed from two glucose molecules. [1 mark] Question 2 continues on the next page 8 *08* IB/M/Jun22/7402/1 Do not write outside the Scientists investigated the effect of trehalose on the growth rate of C. difficile. box They grew populations of non-resistant and antibiotic-resistant C. difficile on separate agar plates with: • no carbohydrate added • trehalose added. They measured the growth rate of the C. difficile. Figure 2 shows the scientists’ results. Figure 2 0 2 . 3 Describe how the scientists could use aseptic techniques to transfer 0.3 cm3 of C. difficile in liquid culture from a bottle onto an agar plate. [3 marks] 9 *09* Turn over ► IB/M/Jun22/7402/1 Do not write outside the box 0 2 . 4 Use Figure 2 to evaluate whether more trehalose in the diet could be a factor in the increased number of antibiotic-resistant C. difficile infections. [3 marks] Turn over for the next question 10 10 *10* IB/M/Jun22/7402/1 Do not write outside the 0 3 box . 1 Give two features of all prokaryotic cells that are not features of eukaryotic cells. [1 mark] 1 2 Many multicellular organisms produce antimicrobial polypeptides (APs) that protect them against prokaryotes. Figure 3 shows how one type of AP acts on the cell-surface membrane of prokaryotes. Figure 3 0 3 . 2 This AP has a secondary structure in a helical shape. Tick () the box to show which type of bond maintains the helical structure of the polypeptide. [1 mark] Disulfide Hydrogen Ionic Peptide 11 *11* Turn over ► IB/M/Jun22/7402/1 Do not write outside the box 0 3 . 3 The amino acids on one side of each AP helix have hydrophobic properties. The amino acids on the opposite side of each helix have hydrophilic properties. Figure 4 shows this. Figure 4 Suggest how these properties of the APs allow them to become positioned across the membrane (as shown in Figure 3) and make a channel through which ions can pass. [2 marks] Question 3 continues on the next page 12 *12* IB/M/Jun22/7402/1 Do not write outside the Figure 5 shows further information about a channel formed in the cell box -surface membrane by the APs. Figure 5 0 3 . 4 Use Figure 5 to calculate the cross-sectional area of the channel through which ions can pass. Assume the cross-sectional area is circular. Use π = 3.14 in your calculation. Give your answer in nm2 and to 1 decimal place. [2 marks] Answer nm2 13 *13* Turn over ► IB/M/Jun22/7402/1 Do not write outside the box 0 3 . 5 The APs damage prokaryotic cells but do not damage the eukaryotic cells in the organisms that produce them. Prokaryotic cell membranes do not contain cholesterol. Assess why the APs do not damage the eukaryotic cells of the organisms that produce them. [2 marks] 0 3 . 6 Scientists observed these APs on prokaryotes using a transmission electron microscope. They stained the APs using a monoclonal antibody with gold attached to it. Suggest how these techniques allowed observation of APs on prokaryotes. [3 marks] 11 14 *14* IB/M/Jun22/7402/1 Do not write outside the There are no questions printed on this page box DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED 15 *15* Turn over ► IB/M/Jun22/7402/1 Do not write outside the box 0 4 . 1 Describe viral replication. [3 marks] 0 4 . 2 Complete Table 2 by putting a tick () where the feature is part of a cell cycle involving mitosis or a cell cycle involving binary fission. [2 marks] Table 2 Feature Cell cycle involving: mitosis binary fission Replication of linear DNA Replication of circular DNA Produces 2 daughter cells Produces 4 daughter cells Happens in prokaryotic cells Happens in eukaryotic cells Question 4 continues on the next page 16 *16* IB/M/Jun22/7402/1 Do not write outside the box Figure 6 represents a cell undergoing meiosis. It shows the chromosomes in the parent cell and in the two cells formed after the first meiotic division. The second division of meiosis proceeds normally except that non-disjunction occurs in the chromosome labelled N. Figure 6 0 4 . 3 Complete Figure 6 to show the chromosomes inside the daughter cells formed after the second meiotic division. [2 marks] 17 *17* Turn over ► IB/M/Jun22/7402/1 Do not write outside the Doctors studied babies born with a mutation caused by chromosome box non-disjunction during gamete formation in their mother. They determined each mother’s age at the time of childbirth and whether the non-disjunction happened in the first meiotic division (MM1 error) or in the second meiotic division (MM2 error). Figure 7 shows the doctors’ results. Figure 7 0 4 . 4 A student concluded that there were more mothers of age ˃37 with MM2 errors than with MM1 errors. Using Figure 7 and suitable calculations show why this conclusion is not valid. [2 marks] 9 18 *18* IB/M/Jun22/7402/1 Do not write outside the box 0 5 Two enzymes, P and Q, are proteins with quaternary structure which catalyse the same reaction, but they have different amino acid sequences. 0 5 . 1 Define the quaternary structure of a protein. [1 mark] 0 5 . 2 Explain how two enzymes with different amino acid sequences can catalyse the same reaction. [2 marks] Scientists investigated the effect of pH 8.4 and pH 7.5 on the activity of enzymes P and Q. Figure 8 shows their results. Figure [Show More]
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