Biology > AQA Questions and Marking Scheme > AS BIOLOGY Paper 1 2020 -Question (All)
AS BIOLOGY Paper 1 2020 - scan Materials For this paper you must have: a ruler with millimetre measurements a scientific calculator, which you are expected to use where appropriate. In... structions 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. All working must be shown. Do all rough work in this book. Cross through any work you do not want to be marked. Information The marks for questions are shown in brackets. The maximum mark for this paper is 75. For Examiner’s Use Question Mark 1 2 3 4 5 6 7 8 9 10 TOTAL Do not write outside the box 2 *02* 1 2 Answer all questions in the spaces provided. 0 1 Figure 1 shows part of a DNA molecule. Figure 1 . How many nucleotides are shown in Figure 1? [1 mark] . Name the type of bond labelled X in Figure 1. [1 mark] 0 1 0 1 Do not write outside the box 3 *03* 6 0 1 . 3 The enzymes DNA helicase and DNA polymerase are involved in DNA replication. Describe the function of each of these enzymes. [2 marks] DNA helicase DNA polymerase 0 1 . 4 Adenosine triphosphate (ATP) is a nucleotide derivative. Contrast the structures of ATP and a nucleotide found in DNA to give two differences. [2 marks] 1 2 Turn over ► Do not write outside the box 4 *04* A student investigated the effect of three types of disinfectant on the growth of Lactobacillus bacteria. During the investigation, the student: boiled the agar before pouring the agar plates transferred 0.5 cm3 of a diluted liquid culture of Lactobacillus onto each agar plate left some agar plates as controls added to other agar plates different concentrations of the disinfectants as shown in Table 1 on page 5. After 2 days, she counted the number of colonies of bacteria on each agar plate. 0 2 . 1 Explain the purpose of: [2 marks] boiling the agar transferring the same volume of liquid culture onto each agar plate. 0 2 Do not write outside the box 5 *05* 2 The three disinfectants used by the student were Lysol, propan-2-ol and ammonia. Table 1 shows the student’s results. Table 1 Concentration of disinfectant / arbitrary units Number of colonies of bacteria Lysol Propan-2-ol Ammonia 0 300 300 300 5 0 290 300 10 0 195 295 15 0 0 275 20 0 0 240 . The liquid culture the student transferred was diluted by 1 in 10 000 (10–4 ). Use information in this question to calculate how many bacteria were present in 1 cm3 of undiluted liquid culture. [2 marks] Answer = Question 2 continues on the next page Turn over ► 0 2 Do not write outside the box 6 *06* 3 6 . The student concluded that the minimum concentration of propan-2-ol needed to stop the growth of Lactobacillus was 15 units. This conclusion is incorrect. Describe how you could obtain a more accurate estimate of the minimum concentration of propan-2-ol needed to stop the growth of this species of bacterium. [2 marks] 0 2 Do not write outside the box 7 Turn over for the next question DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED [Show More]
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