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

Question 129

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Question

MCQ▾

Which element is found in a molecule of Chlorophyll?

Choices

Choice (4)
a.Manganese
b.Lead
c.Calcium
d.Magnesium

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).