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 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
Chloroplast Pigments Table
| Pigment group | Name of pigment | Colour of pigment |
| Chlorophylls | Chlorophyll a Chlorophyll b |
Light green Dark green |
| Carotenoids | β carotene Xanthophyll |
Orange Yellow |
- 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
Examiner Tip
Remember – the pigments themselves have colours, which are the colours of the visible light spectrum that they reflect (back into our eyes). This is different from the colours of light that they absorb.
