Lesson 8.2.1

8.2.1 Rod cells, rhodopsin and action potentials in the retina Quiz: Pearson Edexcel Biology, Unit 8

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 8.2.1, Rod cells, rhodopsin and action potentials in the retina: 20 multiple choice questions for the Pearson Edexcel Biology (9BI0), Unit 8: Grey Matter, written with Revision Ninja.

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The 20 questions

  1. Which light-sensitive pigment is found in rod cells?

    • Opsin
    • Iodopsin
    • Rhodopsin
    • Retinal

  2. Which two molecules combine to form the pigment rhodopsin?

    • Opsin and carotene
    • Opsin and retinol
    • Opsin and retinal
    • Iodopsin and retinal

  3. What happens to retinal when rhodopsin absorbs light?

    • Cis to trans
    • Linear to cyclic
    • Trans to cis
    • Alpha to beta

  4. What is the state of sodium ion channels in rod cells in the dark?

    • Inactivated
    • Blocked
    • Open
    • Closed

  5. What change occurs to a rod cell's membrane potential in the light?

    • Repolarisation
    • Action potential
    • Hyperpolarisation
    • Depolarisation

  6. How does hyperpolarisation of a rod cell affect neurotransmitter release?

    • Increases release
    • Decreases release
    • Has no effect
    • Stops release completely

  7. Why can rod cells NOT distinguish between different wavelengths of light?

    • Single photopigment type
    • Absence of retinal
    • Low light sensitivity
    • Lack of neurones

  8. Which region of the retina contains a high density of cones but almost no rods?

    • Optic disc
    • Blind spot
    • Sclera
    • Fovea

  9. Why are there no photoreceptors present at the blind spot?

    • High light intensity
    • Optic nerve exits
    • Excessive cone density
    • Lack of capillaries

  10. What term describes multiple rod cells connecting to a single bipolar cell?

    • Convergence
    • Summation
    • Divergence
    • Accommodation

  11. What is the correct sequence of events in a rod cell exposed to light?

    • Bleaching, depolarisation, closure
    • Closure, bleaching, hyperpolarisation
    • Bleaching, closure, hyperpolarisation
    • Hyperpolarisation, closure, bleaching

  12. Neurotransmitter release falls from 10 units to 2 units in light. What is the percentage decrease?

    • 20%
    • 800%
    • 8%
    • 80%

  13. Which retinal cells produce action potentials along the optic nerve?

    • Cone cells
    • Ganglion cells
    • Rod cells
    • Bipolar cells

  14. Why does sensitivity to light decrease temporarily after exposure to a bright flash?

    • Rhodopsin is bleached
    • Retinal is destroyed
    • Opsin is denatured
    • Sodium channels open

  15. What is the main role of cGMP in rod cells in the dark?

    • Synthesises rhodopsin
    • Inhibits opsin
    • Closes sodium channels
    • Opens cation channels

  16. Why do rod cells fail to function effectively in bright light?

    • Membranes depolarise
    • Opsin is resynthesised
    • Sodium channels open
    • Rhodopsin is bleached

  17. Which feature of rod cells allows high light sensitivity in dim conditions?

    • Individual bipolar connections
    • High visual acuity
    • Retinal convergence
    • Monopolar convergence

  18. Which light-absorbing photopigment is found inside human rod cells?

    • Rhodopsin
    • Phytochrome
    • Melanin
    • Iodopsin

  19. What change occurs to a rod cell membrane potential when absorbing light?

    • Depolarisation
    • Repolarisation
    • Hyperpolarisation
    • Action potential

  20. How does light absorption affect neurotransmitter release from rod cells?

    • Release increases
    • Release decreases
    • Release stops completely
    • Release remains unchanged

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