Chapter 18

1. Pyridoxal phosphate is a cofactor in this class of reactions:

Acetylation.

Desulfuration.

Methylation.

Reduction.

Transamination.

2. Urea synthesis in mammals takes place primarily in tissues of the:

Brain.

Kidney

Liver

Skeletal muscle

Small intestine

3. The coenzyme involved in a transaminase reaction is:

Biotin phosphate.

Lipoic acid.

Nicotinamide adenine dinucleotide phosphate (NADP+).

Pyridoxal phosphate (PLP).

Thiamine pyrophosphate (TPP).

4. The coenzyme required for all transaminations is derived from:

Niacin.

Pyridoxine (vitamin B6).

Riboflavin.

Thiamin.

Vitamin B12.

5. Conversion of ornithine to citrulline is a step in the synthesis of:

Aspartate.

Carnitine.

Pyruvate.

Tyrosine.

Urea.

6. The human genetic disease phenylketonuria (PKU) can result from:

Deficiency of protein in the diet.

Inability to catabolize ketone bodies.

Inability to convert phenylalanine to tyrosine.

Inability to synthesize phenylalanine.

Production of enzymes containing no phenylalanine.

7. Transamination from alanine to -ketoglutarate requires the coenzyme:

Biotin.

NADH.

No coenzyme is involved.

Pyridoxal phosphate (PLP).

Thiamine pyrophosphate (TPP).

8. 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?

High carbohydrate, very low protein

Very high carbohydrate, no protein, no fat

Very very high fat, high carbohydrate, no protein

Very high fat, very low protein

Very low carbohydrate, very high protein

9. The amino acids serine, alanine, and cysteine can be catabolized to yield:

Fumarate.

Pyruvate.

Succinate.

-ketoglutarate.

None of the above.

10. Which of these amino acids can be directly converted into a citric acid cycle intermediate by transamination?

Glutamic acid

Serine

Thronine

Tyrosine

Proline

11. In amino acid catabolism, the first reaction for many amino acids is a(n):

Decarboxylation requiring thiamine pyrophosphate (TPP).

Hydroxylation requiring NADPH and O2.

Oxidative deamination requiring NAD+.

Reduction requiring pyridoxal phosphate (PLP).

Transamination requiring pyridoxal phosphate (PLP).

12. Serine or cysteine may enter the citric acid cycle as acetyl-CoA after conversion to:

Oxaloacetate.

Propionate.

Pyruvate.

Succinate.

Succinyl-CoA.

13. In the digestion of protein that occurs in the small intestine, which enzyme is critical in the activation of zymogens?

Enteropeptidase

Hexokinase

Papain

Pepsin

Secretin

14. Which substance is not involved in the production of urea from NH4 + via the urea cycle?

Asparate

ATP

Carbamoyl phosphate

Malate

Ornithine

15. Which of these amino acids are both ketogenic and glucogenic? 1. Isoleucine 2. Valine 3. Histidine 4. Arginine 5. Tyrosine

1 and 5

1, 3 and 5

2 and 4

2, 3 and 4

2, 4 and 5

16. Which of these directly donates a nitrogen atom for the formation of urea during the urea cycle?

Adenine

Aspartate

Creatine

Glutamate

Ornithine

17. Glutamate is metabolically converted to -ketoglutarate and NH4 + by a process described as:

Deamination.

Hydrolysis.

Oxidative deamination.

Reductive deamination.

Transamination.

18. Which of the following statements is false in reference to the mammalian synthesis of urea?

Krebs was a major contributor to the elucidation of the pathway involved.

The amino acid arginine is the immediate precursor to urea.

The carbon atom of urea is derived from mitochondrial HCO3–.

The precursor to one of the nitrogens of urea is aspartate.

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

19. In the urea cycle, ornithine transcarbamoylase catalyzes:

Cleavage of urea to ammonia.

Formation of citrulline from ornithine and another reactant.

Formation of ornithine from citrulline and another reactant.

Formation of urea from arginine.

Transamination of arginine.

20. Which of these is not a protease that acts in the small intestine?

Chymotrypsin

Elastase

Enteropeptidase

Secretin

Trypsin

21. The conversion of glutamate to an -ketoacid and NH4 +:

Does not require any cofactors.

Is a reductive deamination.

Is accompanied by ATP hydrolysis catalyzed by the same enzyme.

Is catalyzed by glutamate dehydrogenase.

Requires ATP.

22. Which of the following is not true of the reaction catalyzed by glutamate dehydrogenase?

It is similar to transamination in that it involves the coenzyme pyridoxal phosphate (PLP).

NH4+ is produced.

The enzyme can use either NAD+ or NADP+ as a cofactor.

The enzyme is glutamate-specific, but the reaction is involved in oxidizing other amino acids.

-Ketoglutarate is produced from an amino acid.

23. Which of the following conversions require more than one step?Which of the following conversions require more than one step? 1. Alanine  pyruvate 2. Aspartate  oxaloacetate 3. Glutamate ketoglutarate 4. Phenylalanine  hydroxyphenylpyruvate 5. Proline  glutamate

1 and 4

1, 2, and 4

1, 3, and 5

2, 4, and 5

4 and 5

24. Which of the following amino acids are essential for humans?

Alanine

Aspartic acid

Aspargenine

Serine

Threorine

25. Tetrahydrofolate (THF) and its derivatives shuttle__________between different substrates.

Electrons

H+

Acyl groups

One carbon units

NH2 groups

26. Which of the following is a zymogen that can be converted to an endopeptidase that hydrolyzes peptide bonds adjacent to Lys and Arg residues?

Chymotrypsinogen

Pepsin

Pepsinogen

Trypsin

Trypsinogen

27. In the human genetic disease maple syrup urine disease, the metabolic defect involves:

A deficiency of the vitamin niacin.

Oxidative decarboxylation.

Synthesis of branched chain amino acids.

Transamination of an amino acid.

Uptake of branched chain amino acids into liver.

Chapter 18

1. Pyridoxal phosphate is a cofactor in this class of reactions:

2.

What first name or nickname would you like us to use?

2. Urea synthesis in mammals takes place primarily in tissues of the:

3. The coenzyme involved in a transaminase reaction is:

4. The coenzyme required for all transaminations is derived from:

5. Conversion of ornithine to citrulline is a step in the synthesis of:

6. The human genetic disease phenylketonuria (PKU) can result from:

7. Transamination from alanine to -ketoglutarate requires the coenzyme:

8. 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?

9. The amino acids serine, alanine, and cysteine can be catabolized to yield:

10. Which of these amino acids can be directly converted into a citric acid cycle intermediate by transamination?

11. In amino acid catabolism, the first reaction for many amino acids is a(n):

12. Serine or cysteine may enter the citric acid cycle as acetyl-CoA after conversion to:

13. In the digestion of protein that occurs in the small intestine, which enzyme is critical in the activation of zymogens?

14. Which substance is not involved in the production of urea from NH4 + via the urea cycle?

15. Which of these amino acids are both ketogenic and glucogenic? 1. Isoleucine 2. Valine 3. Histidine 4. Arginine 5. Tyrosine

16. Which of these directly donates a nitrogen atom for the formation of urea during the urea cycle?

17. Glutamate is metabolically converted to -ketoglutarate and NH4 + by a process described as:

18. Which of the following statements is false in reference to the mammalian synthesis of urea?

19. In the urea cycle, ornithine transcarbamoylase catalyzes:

20. Which of these is not a protease that acts in the small intestine?

21. The conversion of glutamate to an -ketoacid and NH4 +:

22. Which of the following is not true of the reaction catalyzed by glutamate dehydrogenase?

23. Which of the following conversions require more than one step?Which of the following conversions require more than one step? 1. Alanine  pyruvate 2. Aspartate  oxaloacetate 3. Glutamate ketoglutarate 4. Phenylalanine  hydroxyphenylpyruvate 5. Proline  glutamate

24. Which of the following amino acids are essential for humans?

25. Tetrahydrofolate (THF) and its derivatives shuttle__________between different substrates.

26. Which of the following is a zymogen that can be converted to an endopeptidase that hydrolyzes peptide bonds adjacent to Lys and Arg residues?

27. In the human genetic disease maple syrup urine disease, the metabolic defect involves: