Important MCQs on Enzymes

MCQs on Enzymes 



Enzymes are the biocatalyst which enhance the rate of  biochemical reaction by decreasing activation energy. Initially, enzymes react with molecules known as substrates converting it into distinct molecules known as products. They exist in all fluids and tissues of the body. The intracellular enzymes catalyze reactions taking place in metabolic pathways.

Enzymes also have valuable industrial and medical applications. The fermenting of wine, leavening of bread, curdling of cheese, and brewing of beer, The uses of enzymes in medicine include killing disease-causing microorganisms, promoting wound healing, and diagnosing certain diseases.

All enzymes are proteins, except certain nucleic acids, called ribozymes (or catalytic RNAs),

Important MCQs on ENZYMES


1. A __________is a biocatalyst that increases the rate of the reaction without being changed.
a) Aluminum oxide
b) Silicon dioxide
c) Enzyme
d) Hydrogen peroxide
Answer : C

2. The nature of an enzyme is____
a) Lipid
b) Vitamin
c) Carbohydrate
d) Protein
Answer: (d)


3. What is an apoenzyme?
a) It is a protein portion of an enzyme
b) It is a non-protein group
c) It is a complete, biologically active conjugated enzyme
d) It is a prosthetic group
Answer : a


4. the coenzyme of riboflavin (B2)?
a) NAD or NADP
b) FAD and FMN
c) Coenzyme A
d) Thiamine pyrophosphate
Answer : b


5. In alcoholism, this enzyme is elevated?
a) acid phosphatase
b) hepatitis
c) serum glutamate pyruvate trasmittase
d) glutamyl transpeptidase
Answer: (d)


6. Which of this vitamin is associated with the coenzyme Biocytin?
a) Nicotinic acid
b) Thiamine
c) Biotin
d) Pyridoxine
Answer : c


7. With regards to enzyme action, this statement is incorrect
a) Malonate is a competitive inhibitor of succinic dehydrogenase

b) substrate binds with enzyme as its active site

c) non competitve inhibitor binds the enzyme at a site distinct from that binding the substrate

d) addition of lot of succinate does not reverse the inhibition of succinic dehydrogenase
by malonate
Answer: d)


8. What is the count of genes that determine the synthesis of one enzyme?
a) One
b) Four
c) Eight
d) Sixteen
Answer: a


9. Name the enzyme which catalyzes the oxidation-reduction reaction?
a) Transaminase
b) Glutamine synthetase
c) Phosphofructokinase
d) Oxidoreductase
Answer : d


10. What is the function of phosphorylase?
a) Transfer inorganic phosphate
b) Transfer a carboxylate group
c) Use H2O2 as the electron acceptor
d) Transfer amino group
Answer : a


11. Mark the CORRECT function of enzyme, Peptidase?
a) Cleave phosphodiester bond
b) Cleave amino bonds
c) Remove phosphate from a substrate
d) Removal of H2O
Answer : b


12. This enzyme was first isolated and purified in the form of crystals
a) Urease
b) pepsin
c) Amylase
d) Ribonuclease
Answer: a


13. Macromolecule chitin is____
a) a simple polysaccharide
b) sulphur containing polysaccharide
c) phosphorous containing polysaccharide
d) nitrogen containing polysaccharide
Answer: d


14. Which of the following reaction is catalyzed by Lyase?
a) Breaking of bonds
b) Formation of bonds
c) Intramolecular rearrangement of bonds
d) Transfer of group from one molecule to another
Answer : a


15. Which of the following is an example of ligases enzyme?
a) Mutases
b) Epimerases
c) Racemases
d) Carboxylases
Answer : d


16. What is the binding energy?
a) Free energy released in the formation of enzyme-substrate interaction
b) The energy required to form a bond
c) The energy required to bind substrate
d) It is the activation energy
Answer : a


17. Enzyme-driven metabolic pathways can be made more efficient by
a) grouping enzymes into multienzyme free-floating complexes
b) concentrating enzymes with specific cellular compartments
c) fixing enzymes into membranes so they are adjacent to each other
d) all of these
Answer: d


18. Tryptophan synthetase of E.coli, a typical bifunctional oligomeric enzyme consists of
a) a protein A and one subunit A
b) a protein designated A
c) two proteins designated A and B
d) a protein designated B
Answer: c


19. This statement about enzymes is true
a) enzymes accelerate reactions by lowering activation energy

b) enzymes are proteins whose three-dimensional form is key to their function

c) enzymes do not alter the overall change in free energy for a reaction

d) all of these
Answer: d


20. Which of the following is not a catalytic strategy for an enzyme to perform specific reaction?
a) Covalent catalysis
b) Metal ion catalysis
c) Michaelis constant
d) Acid-base catalysis
Answer : c


21. What is the SI unit of enzyme activity?
a) Km
b) Kat
c) Kcat
d) Vmax
Answer : b


22. The enzyme COX-1 is vital for human health in this way:
a) it is a chemical derivative of aspirin

b) catalyzes the hormone-production which maintains the stomach lining

c) critical for the biosynthesis of DNA

d) helps in the transportation of carbon dioxide in the blood
Answer: b


23. Which of the following is not an example of irreversible enzyme inhibitor?
a) Cyanide
b) Sarin
c) Diisopropyl phosphoflouridate (DIPF)
d) Statin drugs
Answer : d


24. Lineweaver-Burk plot is also known as______
a) Double reciprocal plot
b) Hanes-Woolf plot
c) Eadie-Hofstee plot
d) Steady-state equation
Answer : a


25. Name the enzyme which is found in tears, sweat, and an egg white?
a) Ribozyme
b) Lysozyme
c) Zymogen
d) Isozymes
Answer :b


26. What is an Isozyme?
a) Same structure, different function
b) Different structure, the same function
c) Same structure, the same function
d) Different structure, different function
Answer : b


27. Which of the following statement is/are correct about Enzyme:
a) An Enzyme is a protein and is used as a catalyst to accelerate the reaction.
b) Life would not exist without the presence of enzymes.
c) Enzymes participate in cellular metabolic processes.
d) All the above
Answer : D


28. Which enzyme is used in making Baby Foods?
a)Amylase
b)Rennin
c)Trypsin
d)None of the above
Answer. C


29. Name an enzyme that is derived from the stomachs of young ruminant animals and also used in dairy industry to produce cheese?
a) Trypsin
b) Pepsin
c) Liginase
d) Rennin
Answer : D


30. Name an enzyme that digests fat?
a)  Lipase
b) Sucrase
c)  Maltase
d)Fructose
Answer. A


31. Who coined the word enzyme?
a) Wilhelm Kuhne
b)  Alfred Russel
c)  Robert Koch
d) Rosalind Franklin
Answer. A


32. Name an enzyme which is not proteinaceous in nature?
a) Cellulases
b) Xylanases
c) Ribozyme
d) Peptidiase
Answer. C


33. The ‘lock and key hypothesis’ mechanism is related with:
A. Digestion of fat in the body
B. For enzyme specificity
C. For the formation of vacuole
D. Explosives
Answer. B


34. In humans salivary amylase enzyme breaks down starch. The optimum pH for this reaction is:
A. 6
B. 6.2
C. 6.4
D. 6.7
Ans. D


35. Inactive enzymes which are not bound to their cofactors are called
A. Apoenzymes
B. Coenzymes
C. Enzyme inhibitors
D. Holoenzymes
Answer : A


36. Which enzyme is used by the biscuit manufacturers to lower the protein level of flour?
A. Amylase
B. Protease
C. Cellulase
D. Xylanase
Answer. B


37. Fat is hydrolysed by the enzyme known as
a) Trypsin
b) Lipase
c) pepsin
d) Amylase
Answer : b


38. The term apoenzyme is applicable to
a) Simple enzyme
b) Protein part of conjugate enzyme
c) Organic cofactor of a conjugate enzyme
d) Inorganic cofactor of a conjugate enzyme
Answer : b


39. Enzymes___
a) Do not require activation energy
b) Do not change requirement of activation energy
c) Increase requirement of activation energy
d) Lowest requirement of activation energy
Answer : d


40. Zymogen is
a) Enzyme poison
b) Enzyme modulator
c) Enzyme precursor
d) Enzyme inhibitor
Answer : c


41. Allosteric enzyme possesses
a) Active site and an allosteric site
b) Active site and two types of allosteric sites
c) Active site and three types of allosteric sites
d)  Three types of allosteric sites
Answer : d


42. Enzyme generally have
a) Same pH and temperature optima
b) Same pH but different temperature optima
c) Different pH but same temperature optima
d) Different pH and different temperature optima
Answer : a


43. The enzyme which forms the peptide bond is known as
a) Carbonic unhydrase
b) Peptidase
c) Carbohydrase
d) Peptidyl transferase
Answer : d


44. The enzyme, tyrosinase, is activated by
a) Iron
b) Copper
c) Zinc
d) Potassium
Answer : b 


45. Trypsin are active in
a) Acidic
b) Alkaline
c) neutral
d) None of these
Answer : b


46. Which one of the following statements regarding enzyme inhibition is correct?
a) Competitive inhibition is seen when a substrate competes with an enzyme for binding to a inhibitor protein

b) Non Competitive inhibition of an enzyme can be overcome by adding large amount of substrate

c) Non competitive efficiency inhibitors often bind to the enzyme irreversibly

d) Competitive inhibition is seen when the substrate and the inhibitor compete for the active site on the enzyme
Answer : d


47. The catalytic efficiency of two different enzymes can be compared by the__
a) Formation of the product
b) Km value
c) Molecular size of the enzymes
d) pH of optimum value
Answer : b


48. The nuclease enzyme, which begins its attack from free of a polynucleotide, is
a) Polymerase
b) kinase
c) exonclease
d) endonuclease
Answer : c


49. The enzymes enterokinase helps in the conversion of
a) Caseinogens into casein
b) Trypsinogen into trypsin
c) Pepsigenogen into pepsin
d) proteins into polypeptides
Answer : b


50. Which of the following is a typical example ‘feedback inhibition’?
a) Cyanide and cytochrome reaction

b) Sulpha drugs and folic acid synthesizer bacteria

c) allosteric inhibition of hexokinase by glucose- 6 -phosphate

d) Reaction between succinic dehydrogenase and succinic acid
Answer : c


51. Some of the enzymes, which are associated in converting fats into carbohydrates, are present in
a) liposomes
b) golgi bodies
c) glyoxysomes
d) microsomes
Answer : c


52. In which one of the following enzymes, is copper necessarily associated as an activator?
a) tyrosinase
b) Lactic dehydrogenase
c) Carbonic unhydrase
d) Trypsinase
Answer : d