IGCSE Biology Paper-2: Specimen Questions with Answers 139 - 139 of 203
Question 139
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 () .
