TRB PG Assistant - Iron‑sulfur proteins, metalloenzymes and metal storage and transport for Fe, Cu and Zn Online Test (MCQ Quiz)

1. What is the primary role of iron-sulfur (Fe-S) clusters in biological systems?

A) Oxygen transport B) Electron transfer and redox reactions C) Energy storage D) DNA replication

2. Which of the following is a common type of Fe-S cluster found in proteins?

A) [1Fe-1S] B) [2Fe-2S] C) [3Fe-4S] D) All of the above

3. In which cellular process are iron-sulfur proteins critically involved?

A) Photosynthesis and respiration B) Protein synthesis C) Lipid metabolism D) Carbohydrate breakdown

4. What amino acid residue is typically involved in coordinating iron atoms within Fe-S clusters in proteins?

A) Serine B) Cysteine C) Histidine D) Glutamate

5. Which metalloenzyme utilizes iron-sulfur clusters for its catalytic activity in nitrogen fixation?

A) Nitrogenase B) Catalase C) Superoxide dismutase D) Cytochrome P450

6. What is the function of aconitase, a metalloenzyme containing an iron-sulfur cluster?

A) Catalyzing the isomerization of citrate to isocitrate B) Transferring electrons in the electron transport chain C) Detoxifying reactive oxygen species D) Synthesizing heme

7. Which metal is primarily stored in the protein ferritin?

A) Copper B) Zinc C) Iron D) Manganese

8. What is the main function of ferritin in the body?

A) Transporting oxygen B) Storing iron in a soluble and non-toxic form C) Catalyzing metabolic reactions D) Regulating blood glucose levels

9. How is iron transported in the bloodstream?

A) Bound to albumin B) Bound to transferrin C) As free ions D) Encapsulated in lipoproteins

10. What is the role of transferrin in iron metabolism?

A) Releasing iron from storage B) Transporting iron from the intestines and macrophages to cells C) Breaking down iron-containing compounds D) Excreting excess iron

11. Which protein is responsible for transporting copper in the blood?

A) Albumin B) Ceruloplasmin C) Transferrin D) Hemoglobin

12. What is the primary function of ceruloplasmin?

A) Iron transport B) Copper transport and oxidation of Fe(II) to Fe(III) C) Zinc storage D) Oxygen binding

13. Wilson's disease is a genetic disorder characterized by the accumulation of excess which metal in the body?

A) Iron B) Zinc C) Copper D) Manganese

14. Which protein is involved in the cellular uptake and storage of zinc?

A) Metallothionein B) Ferritin C) Transferrin D) Ceruloplasmin

15. What is the primary role of metallothioneins?

A) Iron storage B) Copper transport C) Zinc and copper detoxification and storage D) Electron transfer

16. Which of the following metalloenzymes is involved in the detoxification of reactive oxygen species by converting superoxide radicals to oxygen and hydrogen peroxide?

A) Carbonic anhydrase B) Superoxide dismutase (SOD) C) Alcohol dehydrogenase D) Carboxypeptidase A

17. Which metal is the central atom in carbonic anhydrase, an enzyme crucial for CO2 transport in the blood?

A) Iron B) Copper C) Zinc D) Magnesium

18. What is the function of heme oxygenase, an enzyme containing iron?

A) Synthesizing heme B) Degrading heme and producing biliverdin C) Transporting iron D) Storing copper

19. Which iron-containing protein is responsible for oxygen transport in red blood cells?

A) Myoglobin B) Hemoglobin C) Cytochrome c D) Transferrin

20. Myoglobin, an oxygen-binding protein found in muscle tissue, contains which metal?

A) Copper B) Zinc C) Iron D) Cobalt

21. What is the role of cytochrome P450 enzymes, which often contain heme iron?

A) DNA repair B) Drug metabolism and biosynthesis of steroids C) Energy production D) Hormone regulation

22. Which protein is responsible for transporting zinc from the diet into intestinal cells?

A) ZIP transporters B) ATP-binding cassette (ABC) transporters C) Metallothioneins D) Transferrin

23. What is the typical oxidation state of iron in the active site of many iron-sulfur proteins during electron transfer?

A) +1 B) +2 C) +3 D) Varies between +1 and +3

24. Which of the following is a metalloenzyme that plays a role in DNA synthesis and repair, utilizing zinc?

A) DNA polymerase B) RNA polymerase C) Reverse transcriptase D) Telomerase

25. What is the function of hephaestin, a ferroxidase similar to ceruloplasmin?

A) Iron absorption in the intestine B) Iron release from macrophages C) Copper transport D) Zinc storage

26. Which disease is associated with a deficiency in copper transport due to a defect in the ATP7A protein?

A) Wilson's disease B) Menkes disease C) Hemochromatosis D) Anemia

27. What is the primary mechanism by which metallothioneins bind to zinc and copper?

A) Ionic interactions with carboxylate groups B) Coordination with sulfhydryl groups of cysteine residues C) Hydrogen bonding D) Covalent bonding with nitrogen atoms

28. Which iron-sulfur protein is a key component of the mitochondrial electron transport chain?

A) Ferredoxin B) Aconitase C) Succinate dehydrogenase D) Rubredoxin

29. What is the role of the protein hepcidin in iron homeostasis?

A) Promoting iron absorption B) Degrading iron C) Regulating iron release from cells by degrading ferroportin D) Transporting iron in the blood

30. Which metalloenzyme is involved in the synthesis of neurotransmitters and plays a role in copper metabolism?

A) Tyrosinase B) Dopamine beta-hydroxylase C) Superoxide dismutase D) Carbonic anhydrase

31. What is the structure of the [4Fe-4S] cluster?

A) Four iron atoms coordinated by four sulfide ions B) Four iron atoms coordinated by four cysteine residues C) A cube-like structure with alternating iron and sulfur atoms D) Two iron atoms bridged by two sulfur atoms

32. Which of the following is a characteristic feature of iron-sulfur proteins related to their function?

A) High catalytic turnover rates B) Ability to participate in one-electron redox reactions C) Requirement for ATP hydrolysis D) Involvement in signal transduction

33. What is the primary function of copper in the enzyme superoxide dismutase (Cu/Zn-SOD)?

A) Facilitating electron transfer from superoxide B) Stabilizing the enzyme structure C) Binding to oxygen D) Catalyzing the reduction of hydrogen peroxide

34. Which of the following is a metalloenzyme that uses zinc and is involved in the breakdown of peptides?

A) Carboxypeptidase A B) Alcohol dehydrogenase C) Lysozyme D) Chymotrypsin

35. What is the function of the protein DMT1 (divalent metal transporter 1)?

A) Iron export from cells B) Iron and other divalent metal ion uptake into cells C) Copper transport D) Zinc storage

36. Which iron-storage protein is found within cells and has a hollow core where iron can be deposited as ferric oxyhydroxide polymers?

A) Transferrin B) Ferritin C) Heme D) Myoglobin

37. What is the role of iron in the electron transport chain?

A) Directly producing ATP B) Accepting electrons from NADH and FADH2 C) Acting as a cofactor in cytochromes and iron-sulfur proteins for electron transfer D) Transporting oxygen

38. Which copper-containing enzyme is involved in the synthesis of melanin?

A) Tyrosinase B) Ceruloplasmin C) Superoxide dismutase D) Cytochrome c oxidase

39. What is the typical coordination environment for zinc in metalloenzymes like carbonic anhydrase?

A) Tetrahedral coordination with histidine residues B) Square planar coordination with cysteine residues C) Octahedral coordination with water molecules D) Linear coordination with proline residues

40. Which iron-sulfur cluster is found in ferredoxins and participates in electron transfer in photosynthesis and respiration?

A) [1Fe-1S] B) [2Fe-2S] C) [4Fe-4S] D) [3Fe-4S]

41. What is the significance of the redox activity of iron in biological systems?

A) It allows for the storage of large amounts of energy B) It is essential for catalyzing electron transfer reactions C) It is primarily involved in structural stabilization of proteins D) It helps in the transport of ions across membranes

42. Which protein is responsible for sequestering excess intracellular copper and preventing its toxicity?

A) Ceruloplasmin B) Metallothionein C) ATP7A D) Transferrin

43. What is the role of the protein ferroportin?

A) Iron import into cells B) Iron export from cells C) Copper transport D) Zinc uptake

44. Which metalloenzyme, containing zinc, plays a critical role in maintaining acid-base balance by catalyzing the rapid interconversion of carbon dioxide and water to bicarbonate and protons?

A) Alcohol dehydrogenase B) Carboxypeptidase A C) Carbonic anhydrase D) Superoxide dismutase

45. What is the primary function of copper in cytochrome c oxidase?

A) Binding oxygen B) Transferring electrons to oxygen C) Storing electrons D) Catalyzing the reduction of protons

46. The [2Fe-2S] cluster is commonly found in which type of proteins?

A) Nitrogenase B) Rubredoxin C) Bacterial ferredoxins and plant-type ferredoxins D) Succinate dehydrogenase

47. What is the function of the protein ICP (Iron-Regulated Transporter 1)?

A) Iron export B) Iron import into cells C) Copper transport D) Zinc storage

48. Which metal is essential for the activity of alcohol dehydrogenase, involved in alcohol metabolism?

A) Iron B) Copper C) Zinc D) Manganese

49. What is the function of the protein hemojuvelin in iron homeostasis?

A) Regulating iron absorption in the gut B) Regulating hepcidin expression C) Transporting iron in the blood D) Storing iron in the liver

50. Which of the following is a metalloenzyme containing copper and involved in the breakdown of extracellular matrix components?

A) Lysyl oxidase B) Tyrosinase C) Ceruloplasmin D) Cytochrome P450

Iron‑sulfur proteins, metalloenzymes and metal storage and transport for Fe, Cu and Zn - Online Test

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