The pigments which they absorb light during photosynthesis are called photosynthetic pigments. They are,
(1) Chlorophyll:
Chlorophyll pigments are of various types. Chlorophyll a, b, c, d, e, bacteriochlorophyll etc. Chlorophyll: It is the primary photosynthetic pigment. The chemical formula of chlorophyll is C55H72O5N4Mg.
It contains a methyl group (CH3). Chlorophyll is called primary photosynthetic pigment because it not only absorbs light but it converts absorbed light energy into chemical energy. Chi a absorbs red light and blue light.
(2) Accessory pigments:
The pigments absorb certain wavelengths of light and they pass that absorbed energy to chi a (primary photosynthetic pigment). They do not convert absorbed energy into chemical energy. The transfer of absorbed energy to chi a is called resonance transfer. Chlorophyll b and carotenoids are the accessory pigments.
(3) Chlorophyll:
It is an accessory pigment and its formula is C55H70O6N4Mg.
It differs from chi a in having aldehyde group (CHO). It absorbs red light of 644nm and blue light of 455nm. It transfers absorbed light energy to chla.
(4) Carotenoids:
They are accessory pigments, they are of two types – carotenes (orange) and Xanthophylls (yellow) carotenes are insoluble in water and soluble in organic solvents. Carotenoids are always found associated with chlorophylls and in thylakoids they are present as chromoproteins. Carotenes absorb blue and green lights and transmit red and yellow lights. Carotenoids absorb light of visible spectrum between 450 – 500nm. The formula of carotene is C40H56 (Carotene is hydrocarbon compound).
The formula of Xanthophyll is C40H56O2N4
