Chlorophylls are green pigments present in the thylakoid membrane of chloroplasts. There are several kinds of chlorophyll : chlorophyll a,b,c,d, and e; bacteriochlorophyll a,b,c,d, and e, and bacterioviridin. Chl a and b are the two types widely distributed in higher plants. Chl c is found in diatoms, dinoflagellates, and brown algae. Chl d is present in red algae.
Chlorophylls are insoluble in water and can be extracted only with organic solvents.
The chlorophyll molecule is formed of a head and tail. The head is formed of magnesium-porphyrin. The porphyrin consists of 4 pyrrole rings joined together by CH bridges. A divalent central magnesium is attached with the nitrogen atoms of the four pyrrole rings. The tail is formed of a long chain of carbon atoms called the phytol chain. it is attached to the porphyrin ring. The head is hydrophilic and the tail is lipophilic.
Difference between Chlorophyll a and Chlorophyll b
Chlorophyll a (Chl-a) 
2. It is present in all phototrophs other than bacteria
3. Blue-green in pure state
4. Empirical formula is C55H77O5N4Mg
5. The 3rd carbon of the side group is methyl group (-CH3)
6. Molecular weight is 873
Chlorophyll b (Chl-b)
1. It is the accessory photosynthetic pigment
2. It is present in all phototrophs other than diatoms, cyanobacteria, red and brown algae
3. Olive green in pure state
4. Empirical formula is C55H70O6N4Mg
5. Side group at the 3rd carbon is aldehyde group (-CHO)
6. Molecular weight is 907
