34. In metalloenzymes, the metal centres are covalently linked through the side chains of the amino acid residues. The correct set of amino acids which are involved in the primary coordinates spheres of metalloenzymes is (A) Ala, Leu, His (B) Glu, His, Cys (C) Leu, Glu, Cys (D) Ala, His, Glu (E) Val, Phe, Asn

4. Both ZnS and CaF₂ have a face-centered cubic unit cell where the S²⁻ and Ca²⁺ ions are closest packed in each structure. Which of the following is true? (A) There are 4 tetrahedral holes empty in each structure. (B) In both compounds, one-half of the tetrahedral holes are filled. (C) In both compounds, all the tetrahedral holes are filled. (D) There are 8 Zn²⁺ ions and 4 F⁻ ions in the unit cell. (E) In ZnS, one-half of the tetrahedral holes are filled by Zn²⁺ ions, whereas in CaF₂ all the tetrahedral holes are filled with F⁻ ions.

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