MCQ Amino Acid Oxidation & Production Urea

Question 1

Which of these is not a protease that acts in the small intestine?
A) Chymotrypsin B) Elastase
C) Enteropeptidase D) Secretin
E) Trypsin

Answer 1

D) Secretin

Question 2

Which of the following is a zymogen that can be converted to an endopeptidase that hydrolyzes peptide bonds adjacent to Lys and Arg residues?
A) Chymotrypsinogen B) Pepsin
C) Pepsinogen
D) Trypsin
E) Trypsinogen

Answer 2

E) Trypsinogen

Question 3

In amino acid catabolism, the first reaction for many amino acids is a(n):
A) decarboxylationrequiringthiaminepyrophosphate(TPP).
B) hydroxylation requiring NADPH and O2.
C) oxidative deamination requiring NAD+.
D) reductionrequiringpyridoxalphosphate(PLP).
E) transamination requiring pyridoxal phosphate (PLP).

Answer 3

E) transamination requiring pyridoxal phosphate (PLP).

Question 4

The coenzyme required for all transaminations is derived from:
A) niacin.
B) pyridoxine (vitamin B6).
C) riboflavin.
D) thiamin.
E) vitamin B12.

Answer 4

B) pyridoxine (vitamin B6).

Question 5

The coenzyme involved in a transaminase reaction is:
A) biotinphosphate.
B) lipoic acid.
C) nicotinamide adenine dinucleotide phosphate (NADP+).
D) pyridoxalphosphate(PLP).
E) thiamine pyrophosphate (TPP).

Answer 5

D) pyridoxalphosphate(PLP).

Question 6

Transamination from alanine to α-ketoglutarate requires the coenzyme:
A) biotin.
B) NADH.
C) No coenzyme is involved.
D) pyridoxalphosphate(PLP).
E) thiamine pyrophosphate (TPP).

Answer 6

D) pyridoxalphosphate(PLP).

Question 7

Pyridoxal phosphate is a cofactor in this class of reactions:
A) acetylation.
B) desulfuration. C) methylation. D) reduction.
E) transamination.

Answer 7

E) transamination.

Question 8

Which of the following is not true of the reaction catalyzed by glutamate dehydrogenase?
A) Itissimilartotransaminationinthatitinvolvesthecoenzymepyridoxalphosphate(PLP).
B) NH4+ is produced.
C) The enzyme can use either NAD+ or NADP+ as a cofactor.
D) Theenzymeisglutamate-specific,butthereactionisinvolvedinoxidizingotheraminoacids.
E) α-Ketoglutarate is produced from an amino acid.

Answer 8

A) Itissimilartotransaminationinthatitinvolvesthecoenzymepyridoxalphosphate(PLP).

Question 9

Glutamate is metabolically converted to α-ketoglutarate and NH4+ by a process described as:
A) deamination.
B) hydrolysis.
C) oxidative deamination.
D) reductivedeamination.
E) transamination.

Answer 9

C) oxidative deamination.

Question 10

The conversion of glutamate to an α-ketoacid and NH4+:
A) doesnotrequireanycofactors.
B) is a reductive deamination.
C) is accompanied by ATP hydrolysis catalyzed by the same enzyme.
D) iscatalyzedbyglutamatedehydrogenase.
E) requires ATP.

Answer 10

D) iscatalyzedbyglutamatedehydrogenase.

Question 11

Which of the following conversions require more than one step?
1. Alanine → pyruvate
2. Aspartate → oxaloacetate
3. Glutamate → α−ketoglutarate
4. Phenylalanine → hydroxyphenylpyruvate 5. Proline → glutamate
A) 1and4
B) 1,2,and4
C) 1,3,and5
D) 2,4,and5
E) 4and5

Answer 11

E) 4and5

Question 12

Which substance is not involved in the production of urea from NH4+ via the urea cycle?
A) Aspartate
B) ATP
C) Carbamoyl phosphate
D) Malate
E) Ornithine

Answer 12

E) Ornithine

Question 13

Which of these directly donates a nitrogen atom for the formation of urea during the urea cycle?
A) Adenine B) Aspartate C) Creatine D) Glutamate E) Ornithine

Answer 13

B) Aspartate

Question 14

Conversion of ornithine to citrulline is a step in the synthesis of:
A) aspartate. B) carnitine. C) pyruvate. D) tyrosine. E) urea.

Answer 14

E) urea.

Question 15

In the urea cycle, ornithine transcarbamoylase catalyzes:
A) cleavageofureatoammonia.
B) formation of citrulline from ornithine and another reactant.
C) formation of ornithine from citrulline and another reactant.
D) formationofureafromarginine.
E) transamination of arginine.

Answer 15

formation of citrulline from ornithine and another reactant.

Question 16

Which of the following statements is false in reference to the mammalian synthesis of urea?
A) Krebswasamajorcontributortotheelucidationofthepathwayinvolved.
B) The amino acid arginine is the immediate precursor to urea.
C) The carbon atom of urea is derived from mitochondrial HCO3–.
D) Theprecursortooneofthenitrogensofureaisaspartate.
E) The process of urea production is an energy-yielding series of reactions.

Answer 16

E) The process of urea production is an energy-yielding series of reactions.

Question 17

If a person’s urine contains unusually high concentrations of urea, which one of the following diets has he or she probably been eating recently?
A) Highcarbohydrate,verylowprotein
B) Very high carbohydrate, no protein, no fat
C) Very very high fat, high carbohydrate, no protein
D) Veryhighfat,verylowprotein
E) Very low carbohydrate, very high protein

Answer 17

E) Very low carbohydrate, very high protein

Question 18

Which of these amino acids are both ketogenic and glucogenic?
1. Isoleucine 2. Valine
3. Histidine 4. Arginine 5. Tyrosine
A) 1and5
B) 1,3,and5
C) 2and4
D) 2,3,and4
E) 2,4,and5

Answer 18

A) 1and5

Question 19

The amino acids serine, alanine, and cysteine can be catabolized to yield:
A) fumarate.
B) pyruvate.
C) succinate.
D) α-ketoglutarate.
E) none of the above.

Answer 19

B) pyruvate.

Question 20

Serine or cysteine may enter the citric acid cycle as acetyl-CoA after conversion to:
A) oxaloacetate. B) propionate. C) pyruvate.
D) succinate.
E) succinyl-CoA.

Answer 20

C) pyruvate.

Question 21

The human genetic disease phenylketonuria (PKU) can result from:
A) deficiencyofproteininthediet.
B) inability to catabolize ketone bodies.
C) inability to convert phenylalanine to tyrosine.
D) inabilitytosynthesizephenylalanine.
E) production of enzymes containing no phenylalanine.

Answer 21

C) inability to convert phenylalanine to tyrosine.