This question tests knowledge of metal ion cofactors essential for enzyme function in biological nitrogen fixation, respiration, glycolysis, and antioxidant defense.

Correct Matching

The standard scientific pairing of cofactors from Column I with enzymes from Column II is:

  • P. Cu²⁺ → (ii) Cytochrome oxidase
  • Q. Se → (iv) Glutathione peroxidase
  • R. Ni²⁺ → (v) Urease
  • S. K⁺ → (iii) Pyruvate kinase
  • T. Mo → (i) Nitrogenase

Note: None of the given options (A-D) perfectly match this standard pairing. The closest are options B and D (3/5 correct each). Verify against your question paper image for possible OCR/print errors.

Enzyme Cofactors Matching Table

Cofactor (Column I) Enzyme (Column II) Biological Role
P. Cu²⁺ (ii) Cytochrome oxidase Electron transfer in respiration, reduces O₂ to H₂O at complex IV
Q. Se (iv) Glutathione peroxidase Reduces H₂O₂ and lipid peroxides using GSH to protect cells
R. Ni²⁺ (v) Urease Hydrolyzes urea to ammonia and CO₂ in bacteria/plants
S. K⁺ (iii) Pyruvate kinase Transfers phosphate from PEP to ADP in glycolysis
T. Mo (i) Nitrogenase Catalyzes N₂ to NH₃ in nitrogen fixation

Option Analysis

Option (A) P-(v); Q-(ii); R-(iv); S-(i); T-(iii)

Cu-urease (wrong, needs Ni), Se-cytochrome oxidase (wrong, needs Cu), K-nitrogenase (wrong, needs Mo). 0 correct matches.

Option (B) P-(ii); Q-(v); R-(iv); S-(iii); T-(i)

Cu-cytochrome oxidase (correct), K-pyruvate kinase (correct), Mo-nitrogenase (correct), but Se-urease (wrong), Ni-glutathione peroxidase (wrong). 3/5 correct.

Option (C) P-(v); Q-(i); R-(iii); S-(ii); T-(iv)

Cu-urease (wrong), Se-nitrogenase (wrong), Ni-pyruvate kinase (wrong), K-cytochrome oxidase (wrong), Mo-glutathione peroxidase (wrong). 0 correct.

Option (D) P-(i); Q-(iv); R-(v); S-(iii); T-(ii)

Se-glutathione peroxidase (correct), Ni-urease (correct), K-pyruvate kinase (correct), but Cu-nitrogenase (wrong), Mo-cytochrome oxidase (wrong). 3/5 correct.

Key Biological Facts

  • Nitrogenase (Mo): Molybdenum-iron protein fixes atmospheric N₂ in diazotrophs.
  • Cytochrome c oxidase (Cu): Copper centers (CuA, CuB) in mitochondrial complex IV.
  • Pyruvate kinase (K⁺): Requires potassium ions for glycolytic ATP production.
  • Glutathione peroxidase (Se): Selenocysteine residue detoxifies reactive oxygen species.
  • Urease (Ni): Nickel active site hydrolyzes urea in Helicobacter pylori, plants.