Lesson 6.2.1c

6.2.1c Culturing microorganisms and growth curves Quiz: OCR Biology, Unit 8

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 6.2.1c, Culturing microorganisms and growth curves: 20 multiple choice questions for the OCR Biology (H020), Unit 8: Cloning and biotechnology, written with Revision Ninja.

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The 20 questions

  1. Which phase of a bacterial growth curve shows the maximum rate of cell division?

    • Death phase
    • Lag phase
    • Log phase
    • Stationary phase

  2. What happens to the rate of cell division relative to cell death during stationary phase?

    • Division exceeds death
    • Division equals death
    • Death exceeds division
    • Division stops completely

  3. What primarily occurs in microorganisms during the lag phase of a growth curve?

    • Rapid cell division
    • Enzyme synthesis
    • Spore formation
    • Population decline

  4. In the bacterial population equation N = N0 x 2^n, what does n represent?

    • Final cell number
    • Number of generations
    • Growth rate constant
    • Initial cell number

  5. Why is a serial dilution performed before plating a dense bacterial culture?

    • Kill unwanted bacteria
    • Sterilise the medium
    • Obtain countable colonies
    • Increase cell growth

  6. What term describes the time required for a population of bacteria to double in number?

    • Growth period
    • Death rate
    • Lag time
    • Generation time

  7. Why is each colony on an agar plate assumed to represent one original organism?

    • From many cells
    • From sterile agar
    • From one cell
    • From fungal spores

  8. A culture starts with 100 cells and undergoes 5 generations in closed conditions. How many cells are present?

    • 320
    • 100000
    • 500
    • 3200

  9. A culture with generation time 25 minutes starts with 50 cells. How many cells are present after 100 minutes?

    • 400
    • 1600
    • 800
    • 200

  10. A 0.1 cm3 sample of a 1 in 10,000 dilution yields 150 colonies on an agar plate. What is the original concentration per cm3?

    • 1.5 x 10^9 cells per cm3
    • 1.5 x 10^3 cells per cm3
    • 1.5 x 10^7 cells per cm3
    • 1.5 x 10^5 cells per cm3

  11. A student plots log of cell number against time and obtains a straight line. Which phase is shown?

    • Exponential growth
    • Lag phase
    • Stationary phase
    • Death phase

  12. What main factor causes the death phase in a closed microbial culture?

    • Accumulation of waste
    • Continuous nutrient inflow
    • Excess oxygen supply
    • Rapid enzyme synthesis

  13. If the turbidity of a bacterial culture increases over time, what has occurred?

    • Cell density increased
    • Cell density decreased
    • Toxic waste decreased
    • Nutrient levels increased

  14. Why must microorganisms go through a lag phase when introduced into a fermenter?

    • Undergo rapid division
    • Produce toxic waste
    • Adapt to medium
    • Die off rapidly

  15. Which method is used to count only viable bacteria in a culture?

    • Hemocytometry
    • Serial dilution plating
    • Mass spectrometry
    • Turbidimetry

  16. Why does measuring turbidity not give an accurate count of living bacterial cells?

    • Kills live cells
    • Measures cell volume
    • Requires fluorescent dyes
    • Counts dead cells

  17. A culture of 1000 cells has a generation time of 30 minutes. How long does it take to reach 1,024,000 cells?

    • 30 hours
    • 3 hours
    • 5 hours
    • 10 hours

  18. Why is bacterial doubling time constant during the exponential growth phase?

    • Plentiful nutrients
    • Nutrient exhaustion
    • Cell wall lysis
    • High toxic waste

  19. A suspension of 10^9 cells per cm3 undergoes three successive 1 in 10 dilutions. Then 0.1 cm3 is spread on a plate. How many colonies are expected?

    • 10000
    • 1000
    • 1000000
    • 100000

  20. When investigating the effect of temperature on bacterial growth, which variable must be controlled?

    • Initial inoculum size
    • Bacterial growth rate
    • Absorbance reading
    • Incubation temperature

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