IGCSE Biology Paper-2: Specimen Questions with Answers 139 - 139 of 203

Question 139

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Question

MCQ▾

Which element is found in a molecule of chlorophyll?

Choices

Choice (4)

a.

Magnesium

b.

Iron

c.

Ferrous

d.

Manganese

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 ring.

  • 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, mainly 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 centre.

  • 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 centre.

  • Chlorophyll - a is a bluish-green while chlorophyll - b is olive-green. Both are soluble in organic solvents like alcohol, acetone etc. Chlorophyll - a ( Mg) possesses (methyl group), which is replaced by –CHO (an aldehyde) group in chlorophyll – b ( ).

A molecule of chlorophyll

A Molecule of Chlorophyll

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