Enzyme Technology Multiple Choice Questions on “Enzymes – Proenzyme & Cofactors – 1”.
1. Enzymes which are present in inactive and need to cleaved in order to be activated are referred to as __________
A. cofactors
B. coenzymes
C. isoenzyme
D. proenzyme
Answer: D
Clarification: Enzymes that are present in inactive and need to cleaved in order to be activated are referred to as proenzyme. This is also called as zymogen. Additional non protein group in an enzyme required for its optimal activity is referred to as cofactors. Complex organic or metallo-organic compound in an enzyme is called coenzyme. Two or more enzymes with identical function but the different structure is referred to as isoenzyme.
2. Trypsin is used to activate __________ to form chymotrypsin.
A. pepsinogen
B. trypsinogen
C. chymotrypsinogen
D. prothrombin
Answer: C
Clarification: Chymotrypsin is secreted by the pancreas as Chymotrypsinogen. It is activated in the digestive tract by trypsin, which is proteolytic enzyme and acts by cleaving off a small peptide from N-terminal region of chymotrypsinogen. This leads to conformation changes and creates a binding site for the substrate in the enzyme.
3. Pick the odd one out.
A. Pepsinogen
B. Prothrombin
C. Trypsin
D. Procarboxypeptidase
Answer: C
Clarification: Trypsin is the odd one out as it is the activated form of proenzyme trypsinogen. Whereas pepsinogen, prothrombin, procarboxypeptidase are proenzymes that are activated to form pepsin, thrombin and carboxypeptidase respectively.
4. Which of these is not a cofactor?
A. Folic acid
B. Nickel
C. Biotin
D. Coenzyme A
Answer: B
Clarification: Nickel is a cofactor that is used by urease enzyme. Additional non protein chemical component required for optimum activity of enzymes is referred to as cofactors. Coenzyme is referred to as a complex organic or metallo-organic compound present in an enzyme. Cofactors are folic acid, biotin, coenzyme A, etc.
5. Which of the following enzymes do not use Mg2+ ions as cofactors?
A. Hexokinase
B. Pyruvate kinase
C. Glutathione peroxidase
D. Glucose-6-phosphatase
Answer: C
Clarification: Cofactors are additional non protein chemical components required for optimum activity of the enzyme. The enzymes which use Mg2+ ions as cofactors are hexokinase, pyruvate kinase, and Glucose-6-phosphatase. For glutathione peroxidase enzyme, Se+ is used as the cofactor.
6. Pick the odd one out.
A. Molybdenum
B. Dinitrogenase
C. Iron
D. Manganese
Answer: B
Clarification: Additional non protein chemical component of an enzyme which is required for optimum activity is referred to cofactors. Dinitrogenase is an enzyme that uses molybdenum as a cofactor. Whereas molybdenum, iron and manganese are coenzymes for nitrate reductase, peroxidase and ribonucleotide reductase.
7. Which of the following enzymes do not use Zn2+ ions as cofactors?
A. Carbonic anhydrase
B. Propionyl CoA carboxylase
C. Alcohol dehydrogenase
D. Carboxypeptidase A
Answer: B
Clarification: The following enzymes use Zn2+ ions as cofactors: carbonic anhydrase, alcohol dehydrogenase, carboxypeptidase A and B. Propionyl CoA carboxylase is an enzyme which uses potassium as the cofactor.
8. Which of the following is not a function of coenzyme-pyridoxal phosphate?
A. Transamination
B. Redox reaction
C. Deamination
D. Decarboxylation