IGCSE Biology Paper-1: Specimen Questions with Answers 129 - 129 of 208

Which element is found in a molecule of Chlorophyll?

Answer

d.

Explanation

• Chlorophyll is the main pigment, useful in photosynthesis.
• Chlorophyll shows porphyrin structure.
• It is a large molecule composed of four 5-membered rings called pyrrole rings and a central core of magnesium. A side chain, called the phytol chain extends from one of the pyrrole rings.
• Phytol chain is composed of insoluble carbon and hydrogen atoms and helps to anchor chlorophyll molecules with the thylakoids.
• Chlorophyll is a green pigment because it does not absorb green light, but reflects green light, so gives green colour to the leaves.
• In plants, two kinds of chlorophyll (chlorophyll - a and chlorophyll - b) are present.
• Chlorophyll - a is two or three times more in quantity than chlorophyll - b and acts as the reaction center.
• On absorbing light, the chlorophyll - b molecule is excited and transfers its energy to chlorophyll - a which converts the light energy into electrical energy. Thus, act as reaction center. Chlorophyll - a is a bluish-green while chlorophyll - b is olive-green. Both are soluble in organic solvents like alcohol, acetone etc. Chlorophyll – a (C₅₅H₇₂O₅N₄Mg) possesses – CH₃ (methyl group) , which is replaced by – CHO (an aldehyde) group in chlorophyll – b (C₅₅H₇₀O₆N₄Mg) .