Iron‑sulfur proteins, metalloenzymes and metal storage and transport for Fe, Cu and Zn - Question Bank

1. The protein Rubredoxin contains which type of iron-sulfur cluster?
A) [1Fe-1S]
B) [2Fe-2S]
C) [3Fe-4S]
D) [4Fe-4S]
2. 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
3. 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
4. Which metal is essential for the activity of alcohol dehydrogenase, involved in alcohol metabolism?
A) Iron
B) Copper
C) Zinc
D) Manganese
5. 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
6. 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
7. 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
8. 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
9. What is the role of the protein ferroportin?
A) Iron import into cells
B) Iron export from cells
C) Copper transport
D) Zinc uptake
10. Which protein is responsible for sequestering excess intracellular copper and preventing its toxicity?
A) Ceruloplasmin
B) Metallothionein
C) ATP7A
D) Transferrin
11. 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
12. 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]
13. 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
14. Which copper-containing enzyme is involved in the synthesis of melanin?
A) Tyrosinase
B) Ceruloplasmin
C) Superoxide dismutase
D) Cytochrome c oxidase
15. 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
16. 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
17. 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
18. 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
19. 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
20. 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
21. 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
22. 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
23. 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
24. Which iron-sulfur protein is a key component of the mitochondrial electron transport chain?
A) Ferredoxin
B) Aconitase
C) Succinate dehydrogenase
D) Rubredoxin
25. 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
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 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
28. 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
29. 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
30. 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
31. 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
32. Myoglobin, an oxygen-binding protein found in muscle tissue, contains which metal?
A) Copper
B) Zinc
C) Iron
D) Cobalt
33. Which iron-containing protein is responsible for oxygen transport in red blood cells?
A) Myoglobin
B) Hemoglobin
C) Cytochrome c
D) Transferrin
34. 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
35. 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
36. 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
37. What is the primary role of metallothioneins?
A) Iron storage
B) Copper transport
C) Zinc and copper detoxification and storage
D) Electron transfer
38. Which protein is involved in the cellular uptake and storage of zinc?
A) Metallothionein
B) Ferritin
C) Transferrin
D) Ceruloplasmin
39. 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
40. 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
41. Which protein is responsible for transporting copper in the blood?
A) Albumin
B) Ceruloplasmin
C) Transferrin
D) Hemoglobin
42. 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
43. How is iron transported in the bloodstream?
A) Bound to albumin
B) Bound to transferrin
C) As free ions
D) Encapsulated in lipoproteins
44. 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
45. Which metal is primarily stored in the protein ferritin?
A) Copper
B) Zinc
C) Iron
D) Manganese
46. 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
47. Which metalloenzyme utilizes iron-sulfur clusters for its catalytic activity in nitrogen fixation?
A) Nitrogenase
B) Catalase
C) Superoxide dismutase
D) Cytochrome P450
48. 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
49. In which cellular process are iron-sulfur proteins critically involved?
A) Photosynthesis and respiration
B) Protein synthesis
C) Lipid metabolism
D) Carbohydrate breakdown
50. 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
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