Lesson 3.5.1.2

3.5.1.2 Photosynthesis: limiting factors and investigation Quiz: AQA Biology, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.5.1.2, Photosynthesis: limiting factors and investigation: 20 multiple choice questions for the AQA Biology (7402), Unit 5: Energy transfers in and between organisms, written with Revision Ninja.

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The 20 questions

  1. Which of the following is an environmental factor that limits the rate of photosynthesis?

    • Concentration of carbon dioxide
    • Amount of DNA in the nucleus
    • Number of chloroplasts in a leaf cell
    • Number of ribosomes in the cytoplasm

  2. A plant grows in a greenhouse. Which practice would raise the rate of photosynthesis when light is not limiting?

    • Raising the carbon dioxide concentration
    • Lowering the temperature to below 5 degrees Celsius
    • Reducing the water supply to zero
    • Removing all light

  3. What is meant by a limiting factor?

    • A factor that has no effect on a process
    • A factor that always increases the rate of a process
    • A factor that is produced by the process itself
    • A factor that is in the shortest supply, so it restricts the rate of a process

  4. Light intensity is raised and the rate of photosynthesis increases then levels off. What explains the levelling off?

    • All oxygen has been removed from the leaf
    • Another factor, such as carbon dioxide concentration or temperature, has become limiting
    • Photosynthesis has stopped due to the high light
    • Chlorophyll has run out completely

  5. Which agricultural practice is designed to overcome the limiting effect of low carbon dioxide concentration?

    • Burning fuel in greenhouses to release carbon dioxide
    • Keeping the greenhouse sealed at night
    • Adding salt to the soil
    • Removing all leaves from the crop

  6. Which technique is used to separate photosynthetic pigments from leaves?

    • Chromatography
    • Electrophoresis of proteins
    • Titration
    • Serial dilution

  7. In a chromatography investigation, what does the Rf value for a pigment measure?

    • The distance travelled by the pigment divided by the distance travelled by the solvent front
    • The rate of enzyme activity
    • The number of chloroplasts in the leaf
    • The total mass of pigment in the sample

  8. Leaves from shade-tolerant and shade-intolerant plants are compared by chromatography. What might differ between them?

    • The base sequence of the DNA in the chloroplasts only
    • The carbon dioxide concentration in the leaf
    • The proportions and types of pigments present
    • The number of nuclei in each leaf cell

  9. An investigation uses a redox indicator to measure the effect of a named factor on dehydrogenase activity in chloroplast extracts. Which indicator would be used?

    • Iodine solution, which turns blue-black with starch
    • DCPIP, which changes colour when it is reduced
    • Benedict's reagent, which reacts with reducing sugars only
    • Biuret reagent, which detects peptide bonds

  10. In a dehydrogenase investigation, what is the independent variable most likely to be?

    • The named factor being varied, such as temperature
    • The time taken to measure the colour change only
    • The volume of the chloroplast extract kept constant
    • The colour of the indicator at the end

  11. Why does the rate of photosynthesis plateau at high carbon dioxide concentrations when light and temperature are constant?

    • Light or temperature has become the limiting factor
    • Carbon dioxide has become toxic to chloroplasts
    • Chlorophyll absorbs carbon dioxide instead of light
    • Rubisco is destroyed by carbon dioxide

  12. A student measures oxygen production by pondweed at different light intensities, keeping temperature and carbon dioxide high. Which is the most suitable dependent variable?

    • The number of bubbles produced per minute
    • The temperature of the room
    • The length of the pondweed stem
    • The colour of the pondweed

  13. Which option best describes how temperature affects the rate of photosynthesis at low temperatures?

    • It slows the rate because enzyme-catalysed steps proceed more slowly
    • It has no effect on the light-dependent reaction
    • It increases the rate because cold makes enzymes more active
    • It stops rubisco from fixing carbon dioxide permanently

  14. A greenhouse grower increases carbon dioxide and light together, but the rate levels off. Which step is most useful next?

    • Remove all chlorophyll from the leaves
    • Check whether temperature is now limiting the rate
    • Lower the carbon dioxide to its original level
    • Stop watering the plants

  15. Which investigation design would best test the effect of light intensity on the rate of photosynthesis in pondweed?

    • Vary the distance of a light source and count oxygen bubbles, keeping temperature and carbon dioxide constant
    • Vary the colour of the water and count leaves
    • Vary the pH of the soil and measure chlorophyll colour only
    • Vary the age of the plant and measure its height only

  16. Why must the temperature be controlled in a light intensity experiment on photosynthesis?

    • Temperature determines the number of chloroplasts
    • Temperature directly produces oxygen
    • Temperature removes the need for light
    • Temperature affects enzyme activity, so it would be a confounding variable

  17. When light is the limiting factor, what happens to the rate of photosynthesis as light intensity increases?

    • The rate decreases because chlorophyll is destroyed by light
    • The rate increases as more light energy is absorbed by chlorophyll
    • The rate stays the same because light is not used in the reaction
    • The rate falls because more oxygen is produced

  18. In an investigation of the effect of temperature on pondweed photosynthesis, which variables should be kept constant?

    • Light intensity and carbon dioxide concentration
    • The number of bubbles counted
    • Only the temperature of the water
    • The species of algae used in the comparison

  19. Why does the rate of photosynthesis fall at temperatures above the optimum?

    • Leaves photosynthesise in the dark when they become warm
    • High temperature denatures enzymes such as rubisco, changing the shape of their active sites
    • Carbon dioxide dissolves more readily at high temperature
    • Chlorophyll is produced more slowly in warm conditions only

  20. A leaf extract is mixed with a redox indicator and the time for the colour change is measured. What does a shorter time indicate?

    • Lower light intensity
    • Lower dehydrogenase activity
    • Higher carbon dioxide production
    • Higher dehydrogenase activity

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