• 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?in 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

An example of a photosystem in a chloroplast thylakoid membrane: a light-harvesting cluster of photosynthetic pigments involved in the light-dependent stage of photosynthesis

• There are?two groups?of pigments
  • Chlorophylls
    • Chlorophyll a and b
  • Carotenoids
    • Carotene and xanthophyll

Chloroplast pigments table

• 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