Bioinorganic Chemistry MCQs
CSIR-NET | GATE | IIT-JAM
Q1. The ligand system present in vitamin B12 is:
- porphyrin
- corrin
- phthalocyanine
- crown ether
Q2. Carboxypeptidase contains:
- Zn(II) and hydrolyzes CO₂
- Zn(II) and hydrolyzes peptide bonds
- Mg(II) and hydrolyzes CO₂
- Mg(II) and hydrolyzes peptide bonds
Q3. Superoxide dismutase contains the metal ions:
- Zn(II) and Ni(II)
- Cu(II) and Zn(II)
- Ni(II) and Co(III)
- Cu(II) and Fe(III)
Q4. The reduction of nitrogen to ammonia carried out by the enzyme nitrogenase needs:
- 2 electrons
- 4 electrons
- 6 electrons
- 8 electrons
Q5. In bacterial rubredoxin, the number of iron atoms, sulfur bridges and cysteine ligands respectively are:
- 4, 4, 4
- 2, 2, 4
- 2, 2, 2
- 1, 0, 4
Q6. The oxidation state of iron in met-hemoglobin is:
- Three
- Two
- Four
- Zero
Q7. The changes which occur when O₂ binds to hemerythrin are:
- B and C
- B and D
- A and D
- A and C
Statements:
- A. One iron atom is oxidized
- B. Both the iron atoms are oxidized
- C. O₂ binds to one iron atom and is also hydrogen bonded
- D. O₂ binds to both the iron atoms and is also hydrogen bonded
Q8. The correct set of biologically essential elements is:
- Fe, Mo, Cu, Zn
- Fe, Cu, Co, Ru
- Cu, Mn, Zn, Ag
- Fe, Ru, Zn, Mg
Q9. Based on the behaviour of metalloenzymes, consider the following statements:
- A. In the enzymes, zinc activates O₂ to form peroxide species.
- B. In the enzymes, zinc activates H₂O and provides a zinc-bound hydroxide.
- C. In the oxidases, iron activates O₂ to break the bonding between the two oxygens.
- D. Zinc ion acts as a nucleophile and attacks the peptide carbonyl.
- A and B
- B and C
- C and D
- A and D
Q10. Fe²⁺ porphyrins fail to exhibit reversible oxygen transport and cannot differentiate CO from O₂. However, hemoglobin is free from both these pitfalls. Choose the correct statements:
- A. Fe²⁺ porphyrins undergo μ-oxo dimer formation and the same is prevented in hemoglobin.
- B. Fe-CO bond strength is much lower in hemoglobin when compared to Fe²⁺ porphyrins.
- C. While Fe-CO is linear, Fe-O₂ is bent and is recognized by hemoglobin.
- D. The interlinked four monomeric units in hemoglobin are responsible to overcome the pitfalls.
- A and B
- A and C
- C and D
- B and D
Q11. In oxyhemocyanin, the coordination number, mode of oxygen binding, colour and the net magnetic behaviour of copper ions, respectively are:
- Four, µ-η¹:η¹-O₂⁻, Colourless and paramagnetic
- Five, µ-η²:η²-O₂⁻, Colourless and paramagnetic
- Five, µ-η²:η²-O₂⁻, blue and diamagnetic
- Four, µ-η¹:η¹-O₂⁻, blue and diamagnetic
Q12. Match the metalloproteins with their respective functions:
Metalloproteins: P. Ferritin, Q. Rubredoxin, R. Cobalamin, S. Carbonic anhydrase
Functions: I. Electron transfer, II. Acid-base catalysis, III. Metal storage, IV. Methyl transfer
Q13. Match columns I, II and III:
Metal (I): A. Ni, B. Zn, C. Mo
Enzyme (II): i. Carbonic anhydrase, ii. Xanthine oxidase, iii. Coenzyme F430
End product (III): X. Uric acid, Y. Methane, Z. Carbonic acid
The correct match is:
- A-iii-Y; B-i-Z; C-ii-X
- A-iii-Y; B-ii-X; C-i-Z
- A-ii-X; B-i-Y; C-iii-Z
- A-i-X; B-iii-Z; C-ii-Y
Q14. Choose the correct statements for oxymyoglobin and cytochrome P450 (resting state):
- both contain dianion of protoporphyrin-IX
- they have fifth ligand bonded to metal centre from the protein backbone
- they contain single active site
- they contain metal ion in +3 oxidation state
Options:
- a, b and c
- a, c and d
- a, b and d
- b and c only
Q15. During oxygen transport by hemerythrin, oxygen is bound as:
- O₂ molecule end-on to one Fe center
- O₂²⁻ bridged to two Fe³⁺ centers
- O₂²⁻ bridged to two Fe²⁺ centers
- Superoxide (O₂⁻) bound to one Fe³⁺ center
(Note: Upon binding O₂, both Fe(II) are oxidized to Fe(III), and O₂ is reduced to peroxide O₂²⁻, which bridges the two iron centers.)
Q16. Amongst the following, the group that is bound to the metal ion in coenzyme B₁₂ (active form) is:
- Methyl
- Adenosyl
- Cyanide
- Hydroxyl
Q17. Match the reactions/conversions catalyzed by metalloenzymes (List-1) with the corresponding metalloenzymes (List-2):
List-1 (Reaction/Conversion):
- (A) O₂ + 4 e⁻ + 8 H⁺ → 2 H₂O + 4 H⁺
- (B) R-H + O₂ + 2 H⁺ + 2 e⁻ → R-OH + H₂O
- (C) 2 H₂O₂ → 2 H₂O + O₂
- (D) NH₂-CH₂-CO₂H → NH₂-CH(CH₂OH)-CO₂H
List-2 (Metalloenzymes):
- (I) Cytochrome c oxidase
- (II) Cytochrome P-450
- (III) Coenzyme B₁₂
- (IV) Catalase
Q18. The correct statements about the iron-containing protein haemerythrin are:
- A. In blood, the metalloprotein consists of eight subunits.
- B. The two Fe(II) centres in deoxyhaemerythrin are strongly antiferromagnetically coupled through the Fe–O–Fe bridge.
- C. O₂ is stored by haemerythrin in marine invertebrates.
- D. The active site has Fe(II) bound by histidine, glutamate and cysteine residues.
Options:
- A and B
- A and C
- B and C
- C and D
Q19. Both plastocyanin and azurin act as electron carriers. The amino acid ligand that is not common in their copper-binding sites is:
- Histidine
- Cysteine
- Glycine
- Methionine
Q20. Which of the following are correct statements about metallothioneins?
- A. Metallothioneins bind soft metals such as Cd²⁺ and Hg²⁺.
- B. Cd²⁺ and Hg²⁺ bind in tetrahedral environment.
- C. It can also bind Cu⁺ in a 3-coordinate environment.
- D. Cysteine residues are present in metallothioneins.
Options:
- A and B
- A, B and D
- A, C and D
- A, B, C and D
Q21. The metal ion present in the active site of carboxypeptidase A, which hydrolyzes peptide bonds, is:
- Mg²⁺
- Zn²⁺
- Fe²⁺
- Cu²⁺
Q22. The oxygen-binding protein in marine invertebrates that contains binuclear copper centres is:
- Hemoglobin
- Myoglobin
- Hemocyanin
- Hemerythrin
Q23. The cofactor containing a corrin ring system and involved in methyl transfer reactions is:
- Heme
- Coenzyme B₁₂
- Iron-sulfur cluster
- Molybdenum cofactor
Q24. In nitrogenase enzyme, the metal cluster responsible for nitrogen fixation is:
- [4Fe-4S]
- FeMo-cofactor
- [2Fe-2S]
- Mn cluster
Q25. The protein responsible for iron storage in humans is:
- Transferrin
- Ferritin
- Cytochrome c
- Rubredoxin
Q26. The type of oxygen binding in oxyhemocyanin is:
- End-on to one Cu
- Bridging peroxide (µ-η²:η²)
- Superoxide to Fe
- Hydroperoxide
Q27. Superoxide dismutase enzyme primarily contains which metal ions in its active site (for Cu/Zn SOD)?
- Fe and Mn
- Cu and Zn
- Ni and Fe
- Mo and Fe
Q28. The axial ligand provided by the protein in deoxyhemoglobin is:
- Tyrosine
- Histidine
- Cysteine
- Methionine
Q29. Vitamin B₁₂ contains cobalt in which oxidation state in its resting form?
- Co(I)
- Co(II)
- Co(III)
- Co(IV)
Q30. The non-heme iron protein involved in electron transfer with a single iron centre coordinated by four cysteines is:
- Ferredoxin
- Rubredoxin
- Hemerythrin
- Cytochrome P450