CIE A Level Biology (9700) 2019-2021

Revision Notes

13.1.3 Chloroplast Pigments

Chloroplast Pigments

  • Chloroplasts contain several different photosynthetic pigments within the thylakoids, which absorb different wavelengths of light
    • In places, these thylakoids stack up to form structures known as grana (singular – granum)
    • The thylakoid membrane system provides a large number of pigment molecules in an arrangement that ensures as much light as necessary is absorbed
    • The pigment molecules are arranged in light-harvesting clusters known as photosystems
    • In a photosystem, the different pigment molecules are arranged in funnel-like structures the thylakoid membrane (each pigment molecule passes energy down to the next pigment molecule in the cluster until it reaches the primary pigment reaction centre)
  • The light-dependent stage of photosynthesis occurs in the thylakoid membranes and the thylakoid spaces (the spaces inside the thylakoids)
  • This is why the thylakoid membranes contain the pigments, enzymes and electron carriers required for the light-dependent reactions
  • There are two groups of pigments: primary pigments known as chlorophylls and accessory pigments known as carotenoids

Chloroplast pigments table

Chloroplast Pigments Table, downloadable AS & A Level Biology revision notes

 

  • Chlorophylls absorb wavelengths in the blue-violet and red regions of the light spectrum
    • They reflect green light, causing plants to appear green
  • Carotenoids absorb wavelengths of light mainly in the blue-violet region of the spectrum

Exam Tip

Remember – the pigments themselves have colour (as described in the table). This is different from the colours of light that they absorb.

Author:

Alistair graduated from Oxford University in 2014 with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems and Societies.
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