AQA A-level BIOLOGY FINAL EXAM Paper 1 BEST APPOVED FINAL JUNE 2023

AQA A-level BIOLOGY Paper 1 Wednesday 7 June 2023 Afternoon 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. Answer all questions in the spaces provided. box 0 1 . 1 Give the three structural features found in all virus particles and describe the function of one of these features. [2 marks] 1 2 3 Function of one named feature . Explain why viruses are described as acellular and non-living. [2 marks] . Give one reason why antibiotics are not effective against viruses. [1 mark] . Chitin is a polysaccharide. The chitin monomer is a β-glucose molecule with one OH group replaced by an NHCOCH3 group. NHCOCH3 can be represented by N(Ac). Figure 1 shows the monomer that forms chitin and the chitin polymer. Figure 1 Question 2 continues on the next page box Turn over ► . Chitin keeps the tracheae open in the tracheal system of gas exchange in an insect. Gas exchange does not occur in the tracheae. Explain the importance of one adaptation of the gas exchange surface in the tracheal system of an insect. box [2 marks] . Lignin is a polymer found in the walls of xylem vessels in plants. Lignin keeps the xylem vessel open as a continuous tube. Explain the importance of the xylem being kept open as a continuous tube. [3 marks] Turn over for the next question DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED box Turn over ► . The human disease, malaria, is caused by infection with a single-celled eukaryotic organism. Figure 2 shows a diagram of Plasmodium vivax, one of the species that can cause malaria. Figure 2 Other than the Golgi apparatus, name one structure in Figure 2 which shows that P. vivax is a eukaryote. box [1 mark] 0 3 . 2 Describe two functions of the Golgi apparatus in a eukaryotic cell. [2 marks] 1 2 P. vivax evolved from a common ancestor in Africa. As humans migrated around the world, new strains of P. vivax evolved. P. vivax is now extremely rare in Africa but there are several different strains of P. vivax in other parts of the world. Figure 3 shows a phylogenetic diagram of the evolution of these different strains. Figure 3 . What does Figure 3 suggest is the order of human migration out of Africa? box Tick () one box. Europe, India, East Asia, Central America, South America India, East Asia, Europe, South America, Central America India, Europe, East Asia, Central America, South America South America, Central America, East Asia, Europe, India Question 3 continues on the next page [1 mark] *07* Turn over ► box . In Africa today, most of the human population are resistant to malaria caused by P. vivax. Use your knowledge of natural selection to explain why this resistance is so common in Africa. [4 marks] *0* . Some hospital patients suffer from diarrhoea caused by infection with the bacterium Clostridium difficile. The C. difficile bacteria release toxins. These toxins cause the diarrhoea. The toxins damage the cells lining the ileum, causing them to lose their microvilli. The damage to the cells reduces the absorption of the products of digestion and reduces the absorption of water, resulting in diarrhoea. Explain why the damage to the cells lining the ileum reduces absorption of the products of digestion and why this reduces absorption of water. box [3 marks] Question 4 continues on the next page Turn over ► box . The scientists suggest that the anti-toxin antibody could be given to some patients as a form of passive immunity. Use Figure 4 to suggest how this passive immunity would work and which patients should be offered this anti-toxin antibody. box [3 marks] . To be used as passive immunity treatment, the anti-toxin antibody would be injected. If it was given by mouth, it would be digested. Describe how the anti-toxin antibody would be digested. [3 marks] Turn over for the next question Turn over ► A student investigated the use of cinnamon oil as an antimicrobial substance. She investigated the effect of cinnamon oil on the growth of five different bacterial cultures grown on agar plates. box . The student added 100 mm3 of each bacterial culture from its glass bottle onto a separate agar plate. She spread each bacterial culture evenly over the agar using a spreader. Describe the aseptic techniques she should use. [3 marks] Question 5 continues on the next page box Turn over ► The student kept the plates at 25 °C for 24 hours. Figure 5 shows what one of her plates looked like after 24 hours. Figure 5 The student measured the diameter of the clear zone with no bacterial growth around each well. She made these measurements to the nearest whole mm Table 1 shows her results. Table 1 box Bacterial culture Diameter of clear zone / mm Cinnamon oil Positive control Negative control Bacillus spp. 15 14 0 Staphylococcus aureus 20 17 0 Listeria monocytogenes 18 12 0 Escherichia coli 16 12 0 Klebsiella spp. 14 12 0 Median for all cultures 0 Mean for all cultures 0 Standard deviation for all cultures 2.4 2.2 0