Biochemistry Multiple Choice Questions on “Metabolic Fates of Amino Groups”.
1. Glutamate is metabolically converted to α-ketoglutarate and NH4+ by a process ___________
A. Oxidative deamination
B. Transamination
C. Reductive deamination
D. Deamination
Answer: A
Clarification: Glutamate is metabolically converted to α-ketoglutarate and NH4+ by a process oxidative deamination catalyzed by L-glutamate dehydrogenase.
2. Free ammonia combined with glutamate to yield glutamine by the action of ___________
A. Glutaminase
B. Glutamine synthase
C. Glutamate dehydrogenase
D. Amino transferase
Answer: B
Clarification: The free ammonia is combined with glutamate to yield glutamine by the action of glutamine synthase.
3. Pyridoxal phosphate and its aminate form, pyridoxamine phosphate are tightly bound coenzymes of ___________
A. Amino transferases
B. Glutaminase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: A
Clarification: All aminotransferases have pyridoxal phosphate (PLP) as cofactor.
4. What is the necessary coenzyme for transamination reactions?
A. Pyridoxal phosphate
B. Thiamine pyrophosphate
C. NAD
D. Coenzyme A
Answer: A
Clarification: Pyridoxal phosphate functions as an intermediate carrier of amino groups at the active site of amino transferases.
5. Which is the first step in the catabolism of most L-amino acids once they have reached the liver is promoted?
A. Amino transferases
B. Glutaminase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: A
Clarification: The first step in the catabolism of most L-amino acids once they have reached the liver is removal of the α-amino groups promoted by enzymes called amino transferases or trasaminases.
6. The combined action of aminotransferase and glutamate dehydrogenase is referred as ___________
A. Oxidative deamination
B. Transamination
C. Reductive deamination
D. Transdeamination
Answer: D
Clarification: The combined action of aminotransferase and glutamate dehydrogenase is referred as transdeamination.
7. Glutamine is converted to glutamate and NH4+ by ___________
A. Amino transferases
B. Glutaminase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: B
Clarification: In the tissues of intestine, liver and kidneys, the amide nitrogen is released as ammonium ion in the mitochondria, where glutaminase converts glutamine to glutamate and NH4+.
8. Which of the following operates at an important intersection of carbon and nitrogen metabolism?
A. Amino transferases
B. Glutaminase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: D
Clarification: Glutamate dehydrogenase operates at an important intersection of carbon and nitrogen metabolism.
9. Trypsinogen is converted to its active state by ___________
A. Enteropeptidase
B. Glutaminase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: A
Clarification: Trypsinogen is converted to its active state by enteropeptidase, a proteolytic enzyme secreted by intestinal cells.
10. Which of the following hydrolyzes successive amino-terminal residues from short peptides?
A. Aminopeptidase
B. Enteropeptidase
C. Glutamine synthase
D. Glutamate dehydrogenase
Answer: A
Clarification: Aminopeptidase hydrolyzes successive amino-terminal residues from short peptides.
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