plumiCulturing microorganisms and growth curves: Edexcel International A Level Biology questions
Every Edexcel International A Level Biology exam question on Culturing microorganisms and growth curves (specification points 6.1–6.4), 2019–2025, with its mark scheme and examiner’s report.
Paper
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Exam
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Calculations
Q7(a)(i)
The whole paper ↗Q7(a)(ii)
The whole paper ↗Q7(c)
The whole paper ↗Q7(d)
The whole paper ↗Q7(e)(i)
The whole paper ↗Q7(e)(ii)
The whole paper ↗Q2(a)(i)
The whole paper ↗Q2(a)(ii)
The whole paper ↗Q2(b)
The whole paper ↗Q2(c)(i)
The whole paper ↗Q2(c)(ii)
The whole paper ↗Q6(b)(i)
The whole paper ↗Your answerQ7(b)(i)
The whole paper ↗Q7(b)(ii)
The whole paper ↗Q7(b)(iii)
The whole paper ↗Q3(a)
The whole paper ↗Q3(b)
The whole paper ↗Q3(c)(i)
The whole paper ↗Q3(c)(ii)
The whole paper ↗Q4(c)(ii)
The whole paper ↗
All 44 questions on Culturing microorganisms and growth curves, as a list
- June 2025, Unit 4, Q7(a)(i) (3 marks): Describe how to inoculate the liquid broth using the colonies growing on nutrient agar. (3)
- June 2025, Unit 4, Q7(a)(ii) (2 marks): Suggest why these liquid cultures were shaken in an incubator. (2)
- June 2025, Unit 4, Q7(c) (3 marks): The scientists cultured the bacteria at different pHs and different temperatures. The graphs show the results. Key Number of bacteria Concentration of pigment N
- June 2025, Unit 4, Q7(d) (4 marks): The graph shows the mass of beta-carotene produced and the number of bacteria in the culture as determined by dilution plating. log10 number of bacteria mass of
- January 2025, Unit 4, Q7(e)(i) (2 marks): The graph shows the growth curve for two types of methanotrophs grown in a methane concentration of 500 a.u. The increase in turbidity of the culture was used t
- January 2025, Unit 4, Q7(e)(ii) (1 mark): Suggest why low methane concentrations are not able to support the growth of some methanotrophs, such as methanotroph A. (1)
- June 2024, Unit 4, Q2(a)(i) (2 marks): Explain the importance of using aseptic techniques to culture bacteria. (2)
- June 2024, Unit 4, Q2(a)(ii) (2 marks): Explain one aseptic technique that should be used when culturing bacteria. (2)
- June 2024, Unit 4, Q2(b) (2 marks): Calculate the growth rate constant (k) of these bacteria between 2 hours and 6 hours of culture. (2) Use the equation: k = log N log N 10 t 10 0 t 0.301 where:
- June 2024, Unit 4, Q2(c)(i) (1 mark): Calculate the ratio of the number of bacteria in these two cultures. (1) Answer : 1
- June 2024, Unit 4, Q2(c)(ii) (2 marks): Student P and student Q used different methods for determining the number of bacteria. State which method each student used. Give a reason for your answer. (2)
- June 2024, Unit 4, Q6(b)(i) (1 mark): How many times does the highest concentration need to be diluted to make the lowest concentration? (1) A 5.12 B 51.2 C 512 D 5120
- January 2024, Unit 4, Q7(b)(i) (3 marks): A student had a suspension of yeast cells in a liquid culture and wanted to determine the concentration of yeast cells in this culture. A sample of this culture
- January 2024, Unit 4, Q7(b)(ii) (4 marks): The growth curve for yeast grown in culture has four phases, similar to bacteria grown in culture. Sketch a growth curve on the axes drawn below. Label the axes
- January 2024, Unit 4, Q7(b)(iii) (4 marks): Describe how the student could use a growth curve to determine the exponential growth rate constant for the yeast. (4)
- October 2023, Unit 4, Q3(a) (1 mark): Complete the table to show the increase in cell number between 4 and 6 hours of culture. (1)
- October 2023, Unit 4, Q3(b) (2 marks): Explain the changes during the first six hours of this culture. (2)
- October 2023, Unit 4, Q3(c)(i) (2 marks): Describe the method used in dilution plating. (2)
- October 2023, Unit 4, Q3(c)(ii) (3 marks): The sketch shows the shape of the growth curve produced using dilution plating and colony counts between 8 and 14 hours of this culture. Log10 number of bacteri
- June 2023, Unit 4, Q4(c)(ii) (4 marks): Describe one method that could be used in this study to determine the relative abundance of Streptococcus in a giant panda. (4)
- January 2023, Unit 4, Q1(a) (2 marks): State two precautions that should be taken to ensure that only one type of bacteria is grown in this culture. (2)
- January 2023, Unit 6, Q2(a) (2 marks): Identify one risk that might be encountered when carrying out this technique and how this risk could be reduced. (2) Risk How this risk could be reduced
- January 2023, Unit 6, Q2(b) (3 marks): The growth rate constant (k) for a bacterial population can be found using the equation: log N log N k 10 t 10 0 0 301 . t × Nt is final number of bacteria N0 i
- January 2023, Unit 6, Q2(c)(i) (2 marks): State two abiotic variables that could affect the growth rate of these bacteria. (2) First variable Second variable
- January 2023, Unit 6, Q2(c)(ii) (2 marks): Choose one of the variables you have identified in (c)(i). Describe how this variable could be controlled and the effect it could have on the results if it is n
- October 2022, Unit 4, Q1(a) (1 mark): Which label should be used for the y-axis of this graph? (1) A log10 number of living bacterial cells B log10 total number of bacterial cells C number of living
- October 2022, Unit 4, Q1(b)(i) (2 marks): Explain the importance of using an aseptic technique. (2)
- October 2022, Unit 4, Q1(b)(ii) (2 marks): Explain two aseptic techniques that should be used in dilution plating. (2)
- June 2022, Unit 4, Q2(a) (1 mark): Which method is being used to determine the number of bacteria in this culture? (1) A dilution plating B latency C mass method D optical method (turbidity)
- June 2022, Unit 4, Q2(b) (2 marks): Explain how the Petri dish should have been sealed after the mixture was spread onto the agar. (2)
- June 2022, Unit 4, Q2(c)(i) (1 mark): Which shows the order of the phases of a bacterial growth curve? (1) A exponential → lag → death → stationary B lag → stationary → death → exponential C lag → e
- June 2022, Unit 4, Q2(c)(ii) (1 mark): The bacteria were not growing at their fastest rate in the conditions the student used. How many of the following changes could result in a faster growth rate?
- June 2022, Unit 4, Q2(c)(iii) (2 marks): Calculate the growth rate constant (k) of these bacteria between 4 hours and 10 hours. (2) log N − log N Use the equation: k = 10 t 10 0 × 0 301 . t Give your a
- October 2021, Unit 4, Q5(a)(i) (1 mark): State the meaning of the term aseptic technique. (1)
- October 2021, Unit 4, Q5(a)(ii) (2 marks): Describe two aseptic techniques that could be used in this investigation. (2)
- October 2021, Unit 4, Q5(a)(iii) (2 marks): Explain why using aseptic technique in this investigation is important. (2)
- October 2021, Unit 4, Q5(b) (2 marks): Explain why the microdilution plate had to be incubated at an appropriate temperature for E. coli for 72 hours. (2)
- October 2021, Unit 4, Q5(c)(iii) (2 marks): The MIC for the antimicrobial substance used in row E was in column 4. Describe how a 1 in 2 dilution plating method would have been carried out to achieve the
- January 2020, Unit 4, Q9(a) (1 mark): State the relationship between optical density and the size of the microorganisms. (1)
- January 2020, Unit 4, Q9(b) (2 marks): Calculate how many times more bacterial cells there are than yeast cells if both samples have an optical density of 1.0 a.u. (2) Answer
- January 2020, Unit 4, Q9(c)(i) (1 mark): State the relationship between the number of bacterial cells and optical density. (1)
- January 2020, Unit 4, Q9(c)(ii) (2 marks): Suggest why using optical density to measure the concentration of microorganisms is more accurate at lower concentrations of cells. Use the information in the d
- January 2020, Unit 4, Q9(d) (3 marks): A liquid medium was inoculated with 6 × 103 bacterial cells and the culture was incubated for a period of time. At the end of this incubation period, there were
- January 2020, Unit 4, Q9(e) (6 marks): Explain why one calibration curve cannot be used to determine the growth of all microorganisms. Use all the information in this question and your own knowledge
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