Edexcel International A Level Biology

Revision Notes

5.6 Absorption & Action Spectra

Test Yourself

Absorption & Action Spectra

  • Chloroplasts contain several different photosynthetic pigments within photosystems embedded in the thylakoid membranes
  • Different pigments absorb light of different wavelengths
    • Chlorophylls absorb wavelengths in the blue-violet and red regions of the light spectrum, reflecting green light and appearing green in colour
    • Carotenoids absorb wavelengths of light mainly in the blue-violet region of the spectrum, reflecting yellow and orange light
      • Carotenoids often remain in leaves after the breakdown of chlorophyll in the autumn, giving some leaves their yellow, orange, and red autumn colours

Examples of Photosynthetic pigments Table

Chloroplast Pigments Table

  • The amount of light at different wavelengths absorbed by a particular pigment gives that pigment's absorption spectrum (plural spectra)
    • Because each type of pigment absorbs light at different wavelengths the absorption spectrum of each pigment is different

Absorption spectra of chlorophylls and carotenoids

Different photosynthetic pigments absorb light of different wavelengths, giving different absorption spectra

  • A plant's rate of photosynthesis varies depending on the wavelengths of light available
  • The changing rate of photosynthesis at different wavelengths is known as an action spectrum
  • Action spectra are very closely correlated to the absorption spectra of the different pigments
    • Having several different pigments with different absorption spectra allows plants to photosynthesise under a wider variety of light wavelengths; this extends the action spectra of plants and maximises rates of photosynthesis

Overlay of photosynthetic absorption and action spectra

Plant action spectra are closely related to the absorption spectra of the different photosynthetic pigments

You've read 0 of your 0 free revision notes

Get unlimited access

to absolutely everything:

  • Downloadable PDFs
  • Unlimited Revision Notes
  • Topic Questions
  • Past Papers
  • Model Answers
  • Videos (Maths and Science)

Join the 80,663 Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Naomi H

Author: Naomi H

Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.