Question

The core metal of chlorophyll is
A. Fe
B. Mg
C. Ni
D. Cu

Answer 1

Hint: A chlorophyll is a photosynthetic pigment located in the thylakoid membrane. Chlorophylls are green in colour and are of five types. Chlorophyll ‘a’ is the universal photosynthetic pigment. It possesses an atom that has the atomic number 12.

Complete answer:
Chlorophylls are green in colour and are of five types: a, b, c, d and e. Every one of them dissolves in organic solvents. Chlorophyll 'a' is found in all the oxygen-evolving photosynthetic plants apart from photosynthetic bacteria. Hence, it is called universal photosynthetic pigment.

The chlorophyll molecule is made up of a squarish tetrapyrrole ring known as head and phytol tail. The magnesium atom is present in the central position of the tetrapyrrole ring. The four pyrrole rings of porphyrin heads are linked together by methine bridges forming a ring system. Phytol is an insoluble long chain of carbon and hydrogen ${C_{20}}{H_{39}}OH$ attached to the fourth ring.

Chlorophyll ‘a’ possesses methyl group at third position, which is replaced by CHO (an aldehyde) group in chlorophyll ‘b’. Chlorophylls are synthesized from precursors ‘Protochlorophyll’. Its synthesis starts from glycine and succinyl CoA. Chlorophyll ‘a’ without Mg core is colourless and is called pheophytin. It is an early electron acceptor.

So, the correct answer is option B.

Note: Chlorophylls are lipid-soluble and are found in the green parts of plants. Carotenoids absorb light energy and transfer it to chlorophyll 'a' and thus, act as accessory pigments. They protect the chlorophyll molecules from photo-oxidation by picking up nascent oxygen and converting it into the harmless molecular stage, called shield pigments.