Q.Which of the following elements is present in the centre of porphyrin ring of chlorophyll?

Chlorophylls are the principal light-absorbing pigments of photosynthesis. Each molecule has a flat porphyrin "head" (four linked pyrrole rings with a central Mg2+ ion) that absorbs light, and a long hydrophobic phytol tail that anchors it in the thylakoid membrane. Chlorophyll a ($C_{55}H_{72}MgN_4O_5$) is the universal primary pigment, present at the reaction centre of both photosystems. Chlorophyll b ($C_{55}H_{70}MgN_4O_6$) is the principal accessory chlorophyll of green plants. Chlorophyll c, lacking the phytol tail (more precisely a chlorophyllide, occurring as a c1/c2 mixture), is found mainly in diatoms, brown algae and dinoflagellates. Chlorophyll d ($C_{54}H_{70}MgN_4O_6$), found in some red algae/cyanobacteria, absorbs further toward the far-red for dim-light adaptation. Bacteriochlorophyll (bacteriochlo …