AS BIOLOGY

AS BIOLOGY Paper 1 Monday 13 May 2024 Morning Time allowed: 1 hour 30 minutes 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 75. Answer all questions in the spaces provided. box . 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 . 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 ► . Describe and explain one adaptation of a single alveolus for gas exchange. [2 marks] box . 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. . Describe a biochemical test to show the presence of protein. [2 marks] Question 2 continues on the next page Turn over ► . The student’s test for protein was positive. Explain why. [2 marks] box . 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] . Describe how viruses are replicated. [4 marks] box Question 3 continues on the next page *07* Turn over ► . 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] box . Predict the appearance of the Petri dish if the incubation was extended by a few more hours. [1 mark] *0* . Animal cells replicate during the cell cycle. Figure 4 shows one animal cell at a stage of the cell cycle. Figure 4 Turn over for the next question box Turn over ►