Bioinorganic Chemistry MCQs with Answer for B.Sc.

Bioinorganic Chemistry MCQs with Answer for B.Sc. Students

Syllabus:

Metal ions present in biological systems, classification of elements according to their action in biological system. Na/K-pump, carbonic anhydrase and carboxypeptidase. Excess and deficiency of some trace metals. Toxicity of metal ions (Hg, Pb, Cd and As), reasons for toxicity, Use of chelating agents in medicine.
Iron and its application in bio-systems, Haemoglobin and myoglobin.
Role of Mg²⁺ ions in energy production and chlorophyll. Role of Ca²⁺ in blood clotting, and structural role (bones).

1. The metal ion which is an essential component of hemoglobin?

a) Na⁺
b) Ca²⁺
c) Fe²⁺
d) Zn²⁺

Fe²⁺ is the central ion in hemoglobin responsible for oxygen binding and transport in blood.

2. What is the primary action of the Na⁺/K⁺ ATPase pump?

a) Transports two Na⁺ into and three K⁺ out of the cell
b) Transports three Na⁺ out and two K⁺ into the cell
c) Transports equal numbers of Na⁺ and K⁺ ions
d) Moves K⁺ ions only

The pump exports three Na⁺ ions and imports two K⁺ ions per cycle, maintaining membrane potential and cellular ion homeostasis.

3. Zinc is a key metal ion in which enzyme?

a) Myoglobin
b) Carbonic anhydrase
c) Hemocyanin
d) Hemoglobin

Carbonic anhydrase contains Zn²⁺ at its active site, which is vital for its ability to rapidly convert carbon dioxide to bicarbonate and vice versa.

4. Which trace metal is required for the proper function of carboxypeptidase?

a) Fe²⁺
b) Mg²⁺
c) Zn²⁺
d) Cu²⁺

Carboxypeptidase requires Zn²⁺ at its catalytic site to hydrolyze peptide bonds in proteins.

5. Which describes a main function of iron in biological systems?

a) Bone structure formation
b) Oxygen transport
c) Hormone synthesis
d) Genetic code translation

Iron is an essential component of hemoglobin and myoglobin, where it enables the transport and storage of oxygen in the body.

6. What happens if copper is deficient in the diet?

a) High blood pressure
b) Anemia
c) Hyperglycemia
d) Goitre

Copper is required for iron metabolism, so its deficiency can result in anemia due to impaired hemoglobin synthesis.

7. Which ion is toxic due to its ability to mimic calcium and disrupt biological systems?

a) Mg²⁺
b) Cd²⁺
c) Zn²⁺
d) Fe²⁺

Cadmium (Cd²⁺) can displace calcium ions in biological systems, leading to toxic effects and disruption of cellular processes.

8. How does mercury (Hg) exert its toxic effects?

a) By affecting DNA replication
b) By binding to sulfhydryl groups in proteins
c) By replacing iron in hemoglobin
d) By inhibiting ATP synthesis

Mercury binds strongly to sulfhydryl (-SH) groups in proteins, inhibiting enzyme function and causing cellular toxicity.

9. Which chelating agent is commonly used to treat lead poisoning?

a) EDTA
b) Penicillin
c) Heparin
d) Vitamin B₁₂

EDTA is an effective chelating agent that binds to lead ions, forming complexes that can be excreted in urine.

10. Myoglobin mainly functions in which biological process?

a) Nerve transmission
b) Oxygen storage
c) Glycogen breakdown
d) Calcium transport

Myoglobin is responsible for storing oxygen in muscle tissues, ensuring a supply during intense activity.

11. Which of the following is the correct classification of essential, beneficial, and toxic elements in living organisms.

a) Only essential elements are present
b) All metals are toxic
c) Elements can be essential, beneficial, or toxic depending on concentration
d) No elements are toxic at any dose

An element's role depends on its concentration; it can be essential in trace amounts but toxic at high levels.

12. The ultratrace element for humans is

a) Iron
b) Zinc
c) Selenium
d) Sodium

Selenium is required in extremely small (ultratrace) amounts by the human body for normal function.

13. What is the main physiological cause of iron-deficiency anemia?

a) Decreased calcium uptake
b) Reduced hemoglobin synthesis
c) Excess potassium intake
d) Impaired zinc utilization

Iron deficiency leads to reduced hemoglobin synthesis, lowering the blood's oxygen-carrying capacity and resulting in anemia.

14. Carbonic anhydrase catalyzes the interconversion of:

a) Ammonia and urea
b) Water and hydrogen peroxide
c) Carbon dioxide and bicarbonate
d) Glucose and pyruvate

Carbonic anhydrase rapidly interconverts carbon dioxide and water into bicarbonate and protons, a key reaction for pH regulation.

15. What is a common consequence of excessive intake of selenium?

a) Tooth decay
b) Hair and nail brittleness
c) Visual impairment
d) Muscle hypertrophy

Toxic levels of selenium (selenosis) often present as brittle hair and nails, along with skin lesions and gastrointestinal problems.

16. Arsenic is toxic because it can substitute for which biological component?

a) Phosphate in ATP
b) Potassium in enzymes
c) Calcium in bones
d) Sodium in nerve cells

Arsenic can replace phosphate in biochemical pathways, especially during ATP synthesis, disrupting cellular energy production.

17. Deficiency of iodine in the body leads to:

a) Diabetes
b) Anemia
c) Goitre
d) Rickets

Iodine deficiency impairs thyroid hormone synthesis, often causing enlargement of the thyroid gland known as goitre.

18. Which of the following is NOT an action of chelating agents?

a) Bind metal ions
b) Increase metal toxicity
c) Promote metal excretion
d) Reduce metal bioavailability

Chelators generally reduce the toxicity of metals by tightly binding them for easier excretion and lowering their bioavailability.

19. In what way does lead (Pb) primarily exert toxicity?

a) Enhances ATP production
b) Disrupts heme biosynthesis
c) Increases oxygen binding
d) Repairs DNA mutations

Lead inhibits enzymes required for heme synthesis, resulting in anemia and impaired oxygen transport.

20. The prosthetic group in hemoglobin is known as:

a) Flavin
b) Heme
c) Biotin
d) NADH

The heme group contains an iron ion and is responsible for the oxygen-carrying capacity of hemoglobin.

21. Which trace element is essential for thyroid gland function?

a) Zinc
b) Iron
c) Iodine
d) Copper

Iodine is required for synthesis of thyroid hormones; deficiency results in thyroid gland dysfunction.

22. The primary biological role of Mg²⁺ is:

a) Oxygen transport
b) DNA and ATP stabilization
c) Blood clotting
d) Hormone regulation

Magnesium stabilizes DNA, RNA, and ATP structures and is a necessary cofactor in many enzymatic reactions.

23. What happens during the process of chelation therapy in metal poisoning?

a) Enhancement of metal uptake
b) Conversion of metals to gases
c) Formation of stable, excretable complexes with metals
d) Destruction of all cells containing metals

Chelation therapy binds metal ions, forming complexes that are soluble and can be eliminated from the body, reducing toxicity.

24. Functionality of carbonic anhydrase depends mainly on presence of:

a) Mn²⁺
b) Zn²⁺
c) Co²⁺
d) Mg²⁺

Zinc is coordinated at the enzyme's active site and is essential for catalysis in carbonic anhydrase.

25. Which metal ion is commonly found in cytochromes and is essential for electron transport?

a) Iron
b) Sodium
c) Potassium
d) Calcium

Iron in the form of Fe^2+/3+ cycles between oxidation states and is crucial for the function of electron transport chain cytochromes.

26. Deficiency of which trace element impairs glucose tolerance?

a) Chromium
b) Nickel
c) Cobalt
d) Zinc

Chromium is needed for optimal functioning of insulin, and its deficiency can result in glucose intolerance.

27. Which property makes Pb²⁺ particularly hazardous in biological systems?

a) Poor solubility
b) Mimicks Ca²⁺ in nerves and bones
c) Enhances hemoglobin synthesis
d) Decreases protein binding

Because lead mimics calcium, it can be incorporated into bone and interfere with calcium-dependent processes in nerves.

28. What is the effect of excessive zinc intake?

a) Copper deficiency
b) Iron overload
c) Selenium toxicity
d) Iodine deficiency

High intakes of zinc can inhibit copper absorption, leading to copper deficiency and associated symptoms.

29. What gives myoglobin its ability to store oxygen?

a) A prosthetic phosphate group
b) Iron atom in a heme group
c) Bound magnesium ion
d) Disulfide bridges

The heme group in myoglobin contains Fe²⁺ which reversibly binds oxygen, allowing oxygen storage in muscle.

30. Nickel is considered essential for:

a) Human insulin synthesis
b) Urease activity in plants
c) DNA replication in animals
d) Nerve conduction in mammals

Nickel is an essential component of urease, an enzyme involved in nitrogen metabolism in plants.

31. What is a typical symptom of cadmium toxicity?

a) Liver enlargement
b) Kidney damage
c) Muscle cramps
d) Hypoglycemia

Cadmium accumulates in the kidneys, causing dysfunction and potentially leading to kidney failure over time.

32. The Na⁺/K⁺ ATPase pump is best described as:

a) Uniporter
b) Antiporter
c) Symporter
d) Channel protein

This pump simultaneously moves Na⁺ and K⁺ in opposite directions, hence is an antiporter.

33. The primary metal ion in carboxypeptidase A is:

a) Manganese
b) Copper
c) Zinc
d) Iron

Zinc is crucial for the enzymatic activity of carboxypeptidase A, aiding in peptide bond hydrolysis.

34. Hemoglobin transports oxygen from:

a) Muscles to lungs
b) Lungs to tissues
c) Tissues to blood
d) Digestive tract to liver

Hemoglobin binds oxygen in the lungs and delivers it to tissues throughout the body for cellular respiration.

35. Which statement best describes the role of trace elements?

a) They are toxic at any level
b) Essential in minute amounts for health
c) Replace macronutrients
d) Function only as enzyme inhibitors

Trace elements are vital in very small quantities for proper enzyme function and other physiological activities.

36. What is the main dietary source of iron for humans?

a) Leafy vegetables
b) Red meat
c) Fruits
d) Dairy products

Red meat supplies heme iron, which is absorbed more efficiently than the non-heme iron found in plants.

37. Which enzyme uses Zn²⁺ in its active site to hydrolyze peptide bonds?

a) Carboxypeptidase
b) Hexokinase
c) DNA polymerase
d) Lipase

Carboxypeptidase is a zinc metalloenzyme critical for protein digestion via peptide bond hydrolysis.

38. Select the best description for metalloenzymes:

a) Enzymes lacking metal ions
b) Enzymes with covalently bound metals
c) Enzymes with essential metal ions for activity
d) Inhibitory proteins

Metalloenzymes contain metal ions such as Zn²⁺, Fe²⁺, or Cu²⁺ necessary for their catalytic functions.

39. Which toxicity symptom is associated mainly with chronic arsenic exposure?

a) Gigantism
b) Hyperkeratosis
c) Night blindness
d) Osteoporosis

Chronic arsenic exposure leads to hyperkeratosis, especially thickening of skin on palms and soles.

40. The correct statement about haemoglobin is

a) It has only one polypeptide chain
b) It contains four heme groups
c) It transports carbon dioxide only
d) Iron in hemoglobin is in the Fe³⁺ state

Hemoglobin is a tetrameric protein, each unit having a heme group with Fe²⁺ at its core.

41. In biological systems, potassium (K⁺) functions primarily in:

a) Bone mineralization
b) Nerve impulse transmission
c) Blood clotting
d) Oxygen transport

Potassium is vital for nerve impulse transmission and maintaining cell potential across membranes.

42. The toxicity of cadmium in humans is mainly due to its effect on:

a) Central nervous system
b) Renal tubules
c) Thyroid gland
d) Blood sugar regulation

Cadmium accumulates in the renal tubules causing nephrotoxicity and kidney malfunction.

43. Which of the following would not be classified as a trace element?

a) Magnesium
b) Selenium
c) Chromium
d) Zinc

Magnesium is a macronutrient, needed by the body in relatively large amounts, unlike trace elements.

44. The heme iron of hemoglobin can bind:

a) Two O₂ molecules at once
b) One O₂ molecule per heme group
c) Four O₂ per heme
d) Only carbon dioxide

Each heme group binds a single O₂ molecule, and hemoglobin with four heme groups can bind up to four O₂ molecules in total.

45. When can a metal ion be considered as “beneficial” in biological systems?

a) Always, regardless of dose
b) Only under deficiency states
c) When it enhances physiological function without toxicity
d) Only as an enzyme cofactor

Beneficial elements improve physiological functions at specific concentrations, but can be harmful if levels are too high.

46. How does EDTA act as a chelating agent?

a) By precipitating metal ions
b) By redox reactions
c) By binding to metals at multiple coordination sites
d) By hydrolyzing metal complexes

EDTA has multiple donor atoms that bind strongly to metals, forming stable, soluble complexes that can be excreted.

47. What is the net charge movement in one cycle of the Na⁺/K⁺ ATPase?

a) No net charge
b) One positive charge out
c) Two positive charges in
d) One negative charge in

As three Na⁺ are moved out and only two K⁺ enter, there is a net movement of one positive charge out of the cell per cycle.

48. Which metal ion is implicated in “Minamata disease”?

a) Zinc
b) Mercury
c) Lead
d) Cadmium

Mercury, especially in its organic methylmercury form, caused neurological symptoms in Minamata disease.

49. What generally determines whether an element acts as nutrient or toxin in the body?

a) Only its atomic radius
b) Its concentration in the organism
c) The color of its compounds
d) Mode of administration

The concentration of an element is the major factor in determining its nutritional or toxic effect in the body.

50. The Fe²⁺ in hemoglobin is coordinated by:

a) Four nitrogen atoms of the porphyrin ring and one histidine
b) Four oxygen atoms of the globin chain
c) One nitrogen and three phosphorus atoms
d) Two sulfur and two nitrogen atoms

The iron ion in the heme is ligated by four nitrogen atoms of the porphyrin ring and histidine residues from the globin protein.

51. What is the role of Mg²⁺ ions in cellular energy production?

a) Structural support only
b) Transport of sodium
c) Acts as a cofactor for ATP-utilizing enzymes
d) Regulates pH only

Mg²⁺ ions stabilize ATP and are vital for the activity of enzymes involved in energy production.

52. Chlorophyll contains which essential metal ion at its core?

a) Iron
b) Magnesium
c) Zinc
d) Copper

Magnesium is the central metal ion in chlorophyll molecules, enabling photosynthetic light absorption.

53. The main source of calcium for structural functions in the body is:

a) Hair
b) Bones and teeth
c) Plasma
d) Liver tissues

Calcium is primarily stored in bones and teeth, providing rigidity and structural support.

54. Which property of Mg²⁺ is vital for its biological functions?

a) Large ionic radius
b) High redox activity
c) Small ionic radius and strong hydration
d) Colorless solutions

The small size and strong hydration of Mg²⁺ favor its role in stabilizing nucleotide triphosphates such as ATP.

55. Which of the following is a structural role of Ca²⁺ in mammals?

a) Component of ATP
b) Constituent of ribosomes
c) Main mineral in bones and teeth
d) Electron transport chain

Calcium forms hydroxyapatite crystals, which provide strength and structure to bones and teeth.

56. Which main function does Ca²⁺ serve in blood clotting?

a) Acts as a hormone
b) Coenzyme in ATP production
c) Cofactor that activates various clotting factors in the cascade
d) Inhibits hemoglobin formation

Ca²⁺ is essential as a cofactor for multiple enzymes and proteins that drive the blood clotting cascade.

57. What happens if Mg²⁺ is absent in a biochemical ATP-requiring reaction?

a) ATP is more reactive
b) Reaction proceeds faster
c) Reaction rate drops dramatically
d) No effect at all

In the absence of Mg²⁺, many ATP-dependent enzymes cannot function effectively, reducing reaction rates sharply.

58. Ca²⁺ serves as a secondary messenger in:

a) Hemoglobin oxygen transport
b) DNA replication
c) Cellular signaling pathways
d) Cell wall synthesis in plants

Calcium ions (Ca²⁺) act as secondary messengers in numerous signal transduction pathways.

59. What is a medicinal example involving bioinorganic chemistry?

a) Cisplatin used in chemotherapy
b) DNA isolation
c) Glucose monitoring
d) PCR amplification

Cisplatin, a platinum-containing inorganic compound, is used to treat certain cancers, demonstrating applications of bioinorganic chemistry in medicine.

60. Which statement best describes the role of Ca²⁺ ions in blood clotting?

a) They only strengthen blood vessels
b) They act as cofactors activating multiple clotting factors in the coagulation cascade
c) They break down fibrin clots
d) They transport oxygen in blood

Calcium ions (Ca²⁺), also known as clotting factor IV, are essential cofactors in multiple steps of the blood coagulation cascade, including the activation of prothrombin to thrombin, which ultimately leads to the formation of fibrin and the blood clot. Deficiency or removal of Ca²⁺ blocks blood coagulation entirely.

Bioinorganic Chemistry MCQs with Answer for B.Sc.