Q.Cytochrome oxidase contains __________ mineral.

Each mineral has a signature biochemical role: Molybdenum → nitrogenase, Zinc → auxin synthesis, Magnesium → chlorophyll, Sulphur → sulphur-containing amino acids like methionine — giving (1)-(iv), (2)-(iii), (3)-(i), (4)-(ii).

Match each mineral to its well-known biochemical function:

(1) Molybdenum — an essential component/cofactor of the enzyme nitrogenase (used by nitrogen-fixing organisms to reduce atmospheric N2) and also of nitrate reductase → matches (iv) Nitrogenase.

(2) Zinc — required for the biosynthesis of the auxin indole-3-acetic acid (IAA), and it activates several enzymes → matches (iii) Auxin.

(3) Magnesium — is the central metal atom coordinated within the porphyrin ring of the chlorophyll molecule; without magnesium, chlorophyll cannot be formed → matches (i) Chlorophyll.

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Cytochrome oxidase, the enzyme that catalyses the final electron-transfer step to oxygen in respiration, contains copper as its essential mineral component.

Among the essential micronutrients required by plants, copper (Cu) plays a key catalytic role as a component of the active sites of several important enzymes involved in redox reactions — such as cytochrome oxidase, plastocyanin (involved in photosynthetic electron transport), and various oxidases. Copper's ability to readily cycle between its Cu+ and Cu2+ oxidation states makes it well suited to electron-transfer reactions.

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Carbonic anhydrase is a zinc-dependent (Zn2+-activated) enzyme.

Many plant enzymes require a specific mineral element (usually a trace/micronutrient) bound at or near their active site to be catalytically active — this is one of the main physiological roles of micronutrients in mineral nutrition.

Carbonic anhydrase catalyses the reversible reaction CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-. It is a well-known zinc metalloenzyme: a Zn2+ ion held in the active site polarises a water molecule, which then attacks CO2 — this is essential for its catalytic mechanism. Without zinc, the enzyme cannot function, which is one reason zinc deficiency in plants affects processes like photosynthesis and CO2 exchange.

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