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Microbial techniques: Edexcel A‑Level Biology B questions

Every Edexcel A-Level Biology B exam question on 6.1 Microbial techniques, 2016–2025, with its mark scheme and examiner’s report.

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1,826 questions

  1. Q11(a)(i)

    June 2025 · Paper 3

    2 marks6.1 Microbial techniques
    The whole paper ↗
    June 2025 Paper 3, question 11(a)(i): Calculate the number of bacteria per cm3 in the original culture. Give your answer in standard form. (2) Answer per cm3

  2. Q11(a)(ii)

    June 2025 · Paper 3

    4 marks6.1 Microbial techniques
    The whole paper ↗
    June 2025 Paper 3, question 11(a)(ii): The graph shows the population of bacteria in a culture, as determined using this method. Log10 number of bacteria 0 1 2 3 4 5 6 7 8 9 10 11 Time / hours Explai

  3. Q11(a)(iii)

    June 2025 · Paper 3

    2 marks6.1 Microbial techniques
    The whole paper ↗
    June 2025 Paper 3, question 11(a)(iii): Between 1.3 hours and 4.7 hours the number of bacteria is rising very rapidly. The number of bacteria can be calculated at any time in this period using the exp

  4. Q11(a)(iv)

    June 2025 · Paper 3

    1 mark6.1 Microbial techniques
    The whole paper ↗
    June 2025 Paper 3, question 11(a)(iv): Calculate the mean generation time, g (time for the population of bacteria to double, in minutes). Use your value for k and the formula k = 60 g (1) Answer minu

  5. Q11(b)

    June 2025 · Paper 3

    4 marks6.1 Microbial techniques
    The whole paper ↗
    June 2025 Paper 3, question 11(b): An alternative method to dilution plating is to use a colorimeter to measure the turbidity of a culture. Turbidity is an indicator of the growth of the bacteria

  6. Q7(a)

    June 2024 · Paper 3

    6 marks6.1 Microbial techniques
    The whole paper ↗
    June 2024 Paper 3, question 7(a): A student investigated the antibacterial properties of turmeric. The student suggested the hypothesis: An extract made from turmeric root will reduce the growth

  7. Q5(b)(i)

    June 2023 · Paper 3

    4 marks6.1 Microbial techniques
    The whole paper ↗
    June 2023 Paper 3, question 5(b)(i): Describe the method used to isolate individual species from a mixed culture of bacteria in nutrient broth. (4)

  8. Q5(b)(ii)

    June 2023 · Paper 3

    3 marks6.1 Microbial techniques
    The whole paper ↗
    June 2023 Paper 3, question 5(b)(ii): Explain three precautions that would be taken to reduce the growth of pathogenic bacteria. (3)

  9. Q11(a)(i)

    June 2022 · Paper 3

    2 marks6.1 Microbial techniques
    The whole paper ↗
    June 2022 Paper 3, question 11(a)(i): Calculate the percentage increase in the number of yeast cells from 2 hours to 6 hours. (2) Answer %

  10. Q11(a)(ii)

    June 2022 · Paper 3

    1 mark6.1 Microbial techniques
    The whole paper ↗
    June 2022 Paper 3, question 11(a)(ii): Predict the number of cells per cm3 of the culture at 12 hours. Assume that the culture continues to grow at the same rate. (1) Answer × 102 per cm3

  11. Q11(b)

    June 2022 · Paper 3

    2 marks6.1 Microbial techniques
    The whole paper ↗
    June 2022 Paper 3, question 11(b): Describe two precautions that would prevent the yeast culture becoming contaminated with bacteria. (2)

  12. Q11(c)(i)

    June 2022 · Paper 3

    2 marks6.1 Microbial techniques
    The whole paper ↗
    June 2022 Paper 3, question 11(c)(i): The volume of liquid in the counting square shown is 0.004 mm3 . (Source: © Joseph Elsbernd/Flickr) Calculate the number of yeast cells per mm3 . Give your answ

  13. Q11(c)(ii)

    June 2022 · Paper 3

    2 marks6.1 Microbial techniques
    The whole paper ↗
    June 2022 Paper 3, question 11(c)(ii): Identify two causes of inaccuracy in this method of counting cells. (2)

  14. Q11(d)(i)

    June 2022 · Paper 3

    3 marks6.1 Microbial techniques
    The whole paper ↗
    June 2022 Paper 3, question 11(d)(i): The student calculated the standard deviations using the following formula.  x 2 x SD n 1 Calculate the standard deviation for the sample at 3 hours. (3) Answe

  15. Q11(d)(ii)

    June 2022 · Paper 3

    3 marks6.1 Microbial techniques
    The whole paper ↗
    June 2022 Paper 3, question 11(d)(ii): The student concluded that the yeast population doubles every 90 minutes. Comment on the validity of this conclusion. (3)

  16. Q8(a)(i)

    October 2020 · Paper 1

    4 marks6.1 Microbial techniques
    The whole paper ↗
    October 2020 Paper 1, question 8(a)(i): Describe how these types of bacteria present in the female genital tract could be identified. (4)

  17. Q8(a)(ii)

    October 2020 · Paper 1

    3 marks6.1 Microbial techniques
    The whole paper ↗
    October 2020 Paper 1, question 8(a)(ii): The photograph shows Lactobacilli on a skin cell from the female genital tract. { skin cell from the chains of female genital tract Lactobacilli Source: © Janic

  18. Q6(b)

    October 2020 · Paper 3

    2 marks6.1 Microbial techniques
    The whole paper ↗
    October 2020 Paper 3, question 6(b): Explain why preventing the replication of DNA produces aseptic conditions. (2)

  19. Q6(c)

    October 2020 · Paper 3

    2 marks6.1 Microbial techniques
    The whole paper ↗
    October 2020 Paper 3, question 6(c): Aseptic conditions are used when growing bacteria in laboratories. Justify two methods, other than UV radiation, for ensuring aseptic conditions. (2)

  20. Q6(d)(ii)

    October 2020 · Paper 3

    2 marks6.1 Microbial techniques
    The whole paper ↗
    October 2020 Paper 3, question 6(d)(ii): In this investigation, living bacteria of each species were exposed to UV radiation for four hours. The numbers of living bacteria were counted each hour during
All 30 questions on Microbial techniques, as a list
  1. June 2025, Paper 3, Q11(a)(i) (2 marks): Calculate the number of bacteria per cm3 in the original culture. Give your answer in standard form. (2) Answer per cm3
  2. June 2025, Paper 3, Q11(a)(ii) (4 marks): The graph shows the population of bacteria in a culture, as determined using this method. Log10 number of bacteria 0 1 2 3 4 5 6 7 8 9 10 11 Time / hours Explai
  3. June 2025, Paper 3, Q11(a)(iii) (2 marks): Between 1.3 hours and 4.7 hours the number of bacteria is rising very rapidly. The number of bacteria can be calculated at any time in this period using the exp
  4. June 2025, Paper 3, Q11(a)(iv) (1 mark): Calculate the mean generation time, g (time for the population of bacteria to double, in minutes). Use your value for k and the formula k = 60 g (1) Answer minu
  5. June 2025, Paper 3, Q11(b) (4 marks): An alternative method to dilution plating is to use a colorimeter to measure the turbidity of a culture. Turbidity is an indicator of the growth of the bacteria
  6. June 2024, Paper 3, Q7(a) (6 marks): A student investigated the antibacterial properties of turmeric. The student suggested the hypothesis: An extract made from turmeric root will reduce the growth
  7. June 2023, Paper 3, Q5(b)(i) (4 marks): Describe the method used to isolate individual species from a mixed culture of bacteria in nutrient broth. (4)
  8. June 2023, Paper 3, Q5(b)(ii) (3 marks): Explain three precautions that would be taken to reduce the growth of pathogenic bacteria. (3)
  9. June 2022, Paper 3, Q11(a)(i) (2 marks): Calculate the percentage increase in the number of yeast cells from 2 hours to 6 hours. (2) Answer %
  10. June 2022, Paper 3, Q11(a)(ii) (1 mark): Predict the number of cells per cm3 of the culture at 12 hours. Assume that the culture continues to grow at the same rate. (1) Answer × 102 per cm3
  11. June 2022, Paper 3, Q11(b) (2 marks): Describe two precautions that would prevent the yeast culture becoming contaminated with bacteria. (2)
  12. June 2022, Paper 3, Q11(c)(i) (2 marks): The volume of liquid in the counting square shown is 0.004 mm3 . (Source: © Joseph Elsbernd/Flickr) Calculate the number of yeast cells per mm3 . Give your answ
  13. June 2022, Paper 3, Q11(c)(ii) (2 marks): Identify two causes of inaccuracy in this method of counting cells. (2)
  14. June 2022, Paper 3, Q11(d)(i) (3 marks): The student calculated the standard deviations using the following formula.  x 2 x SD n 1 Calculate the standard deviation for the sample at 3 hours. (3) Answe
  15. June 2022, Paper 3, Q11(d)(ii) (3 marks): The student concluded that the yeast population doubles every 90 minutes. Comment on the validity of this conclusion. (3)
  16. October 2020, Paper 1, Q8(a)(i) (4 marks): Describe how these types of bacteria present in the female genital tract could be identified. (4)
  17. October 2020, Paper 1, Q8(a)(ii) (3 marks): The photograph shows Lactobacilli on a skin cell from the female genital tract. { skin cell from the chains of female genital tract Lactobacilli Source: © Janic
  18. October 2020, Paper 3, Q6(b) (2 marks): Explain why preventing the replication of DNA produces aseptic conditions. (2)
  19. October 2020, Paper 3, Q6(c) (2 marks): Aseptic conditions are used when growing bacteria in laboratories. Justify two methods, other than UV radiation, for ensuring aseptic conditions. (2)
  20. October 2020, Paper 3, Q6(d)(ii) (2 marks): In this investigation, living bacteria of each species were exposed to UV radiation for four hours. The numbers of living bacteria were counted each hour during
  21. October 2020, Paper 3, Q6(d)(iii) (4 marks): A student concluded from this investigation that if food is exposed to UV radiation, it would remove all risk of food poisoning. Criticise the validity of this
  22. June 2019, Paper 1, Q2(b)(i) (2 marks): Calculate how many times faster the bacteria in sucrose reproduce than the bacteria in glucose, during the log phase. (2) Answer
  23. June 2019, Paper 1, Q2(b)(ii) (2 marks): Analyse the data to explain why the growth curve for sucrose is different from the growth curve for glucose. (2)
  24. June 2019, Paper 1, Q2(b)(iii) (1 mark): On the graph, draw a curve to show the number of bacteria grown in glucose as determined by the optical method. (1)
  25. June 2018, Paper 1, Q8(b)(i) (4 marks): Salmonella was isolated from a mixed culture of bacteria, using streak plating onto selective media. Explain why this is a suitable method for isolating the Sal
  26. June 2018, Paper 1, Q8(b)(ii) (3 marks): The scientist made a broth culture of Salmonella at a concentration of 5 × 103 cells per cm3. Ten hours later the concentration of Salmonella was 4 × 106 per cm
  27. June 2018, Paper 1, Q8(b)(iii) (3 marks): In this calculation, the scientist did not allow for the time that the Salmonella spent in the lag phase. Explain the effect that this will have on the calculat
  28. June 2018, Paper 3, Q10(d) (5 marks): A student compared the effectiveness of these four antibiotics on the growth of bacteria. Devise a method that the student could use to obtain valid results. (5
  29. June 2017, Paper 1, Q3(a)(ii) (4 marks): Describe the techniques microbiologists could use to confirm that this food poisoning was caused by Staphylococcus. (4)
  30. June 2017, Paper 3, Q1(c) (5 marks): Describe how you would use aseptic techniques to transfer bacterial cells growing on an agar plate to a tube containing a sterile broth. (5)

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