Enzyme Technology Assessment Questions and Answerson “Enzymes – Proenzyme & Cofactors – 2”.
1. Which of the following is not a proenzyme?
A. Prothrombin
B. Pepsinogen
C. Trypsin
D. Trypsinogen
Answer: C
Clarification: Proenzymes either have prefixes pro-like prothrombin, proelastase etc., or suffix–ogen like pepsinogen, trypsinogen, etc. Trypsin is an enzyme and not a proenzyme.
2. Chymotrypsinogen: Chymotrypsin:: Pepsinogen: _____________
A. Pepsin
B. Trypsin
C. Carboxypeptidase
D. Thrombin
Answer: A
Clarification: Chymotrypsin is an activated form of proenzyme chymotrypsinogen. In the same way, pepsin is an activated form of proenzyme pepsinogen. Trypsin, carboxypeptidase and thrombin are activated forms of proenzymes like trypsinogen, procarboxypeptidase and prothrombin respectively.
3. Additional non protein chemical component required for optimum activity of enzymes is referred to as ___________
A. coenzymes
B. holoenzyme
C. cofactors
D. isoenzyme
Answer: C
Clarification: Additional non protein chemical component required for optimum activity of enzymes is referred to as cofactors. Coenzymes are those complex organic or metallo-organic compound present in an enzyme. Holoenzyme is referred to as a complete catalytically active enzyme together with its bound coenzyme and/or metal ion. Isoenzyme is referred to as two or more enzymes with identical function but different structure.
4. Pick the odd one out.
A. Thiamine pyrophosphate
B. FAD
C. NAD
D. Zinc
Answer: D
Clarification: Zinc is the odd one out as it is the cofactor for enzymes such as carbonic anhydrase, alcohol dehydrogenase, carboxypeptidase A and B. Whereas thiamine pyrophosphate, FAD, NAD are coenzymes.
5. Copper: Cytochrome oxidase:: Potassium: _________
A. Arginase
B. Propionyl CoA carboxylase
C. Dintrogenase
D. Catalase
Answer: B
Clarification: Copper acts as cofactor for cytochrome oxidase. In the same way, potassium acts as cofactor for propionyl CoA carboxylase. For arginase, dinitrogenase and catalase, cofactors used are manganese, molybdenum and iron respectively.
6. Which of the following is not an enzyme?
A. Ribonucleotide reductase
B. Selenium
C. Glutathione peroxidase
D. Carbonic anhydrase
Answer: C
Clarification: Enzyme is referred to as a substance which acts as a catalyst to bring about a specific biochemical reaction. Ribonucleotide reductase, Glutathione peroxidase, and Carbonic anhydrase are the enzymes. Whereas selenium is not an enzyme but a cofactor, which are referred to as additional non protein chemical component of an enzyme which is required for optimum activity.
7. Which of the following enzymes do not use Fe2+ or Fe3+ ions as cofactors?
A. Cytochrome oxidase
B. Dinitrogenase
C. Catalase
D. Peroxidase
Answer: B
Clarification: Cofactor are those additional non protein chemical component of an enzyme which are required for its optimum activity. Cytochrome oxidase, catalase, and peroxidase are the enzymes which uses Fe2+ or Fe3+ ions as cofactors. For dinitrogenase, the cofactor used is molybdenum.
8. Coenzyme A: Acyl carrier:: Methylcobalamin: _____________
A. Transketolase reaction
B. Isomerization
C. Carboxylation reaction
D. Carrier of one carbon group
Answer: B
Clarification: Coenzyme A which is also pantothenic acid vitamin has the function of carrying acyl groups. Methylcobalamin which is a coenzyme performs function of isomerization along with the transfer of methyl groups in a reaction. Transketolase reaction, Carboxylation reaction and Carrier of one carbon group are the functions of thiamine pyrophosphate, biocytin and tetrahydrofolate coenzymes.
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