Photosynthetic Pigments

Chlorophylls

Chlorophyll a is the main photosynthetic pigment in most plants. It is directly involved in the light-dependent reactions of photosynthesis and it absorbs light best in the blue-violet and red regions of the light spectrum.
Chlorophyll b is an accessory pigment to chlorophyll a. It has a slightly different structure to chlorophyll a and as such, it absorbs light of differing wavelengths. It serves to widen the range of light that a plant can use in photosynthesis.

Carotenoids are another group of accessory pigments found in the chloroplasts of plants. They absorb light in the blue-green regions of the light spectrum, but also have other functions in the plant, such as to protect chlorophyll from damage.
The types of carotenoids include carotenes, that appear bright red, orange, or yellow, and xanthophylls, which appear yellow.
Lycopene, an example of a carotene, aids in the absorption of light energy and its transfer to chlorophyll a.

These pigments work together to absorb and funnel light energy to the reaction centre where it’s used for photosynthesis.
Different pigments allow the plant to absorb a wider range of light, enhancing the process of photosynthesis.
Some pigments also have protective functions, acting as antioxidants to neutralise harmful free radicals produced in sunlight.

Pigments are arranged in photosystems within the thylakoid membrane of the chloroplast.
Each photosystem contains a number of pigment molecules bound to proteins known as light-harvesting complexes orantenna complexes.
There are two types of photosystems: Photosystem I (PS I) and Photosystem II (PS II).
When a pigment molecule absorbs a photon, the energy is transferred from molecule to molecule until it reaches the reaction centre.
The reaction centre contains a special pair of chlorophyll a molecules that can use the energy from light to boost electrons to a higher energy level where they can be captured and used in the reactions of photosynthesis.