Lehninger biochem test bank

Lehninger biochem test bank 1. Under which circumstances are amino acids not metabolized via oxidative degradation? A) Starvation B) Plants growing in nutrient-rich soils C) Normal protein turnover D) A diet rich in proteins E) Uncontrolled diabetes - ANS B 2. Which of these is not a protease that acts in the small intestine? A) Chymotrypsin B) Elastase C) Enteropeptidase D) Secretin E) Trypsin - ANS D 3. In the digestion of protein that occurs in the small intestine, which enzyme is critical in the activation of zymogens? A) Enteropeptidase B) Hexokinase C) Papain D) Pepsin E) Secretin - ANS A 4. 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 - ANS E 5. In amino acid catabolism, the first reaction for many amino acids is a(n): A) decarboxylation requiring thiamine pyrophosphate (TPP). B) hydroxylation requiring NADPH and O2. C) oxidative deamination requiring NAD+. D) reduction requiring pyridoxal phosphate (PLP). E) transamination requiring pyridoxal phosphate (PLP). - ANS E 6. The coenzyme required for all transaminations is derived from: A) niacin. B) pyridoxine (vitamin B6). C) riboflavin. D) thiamin. E) vitamin B12. - ANS B 7. The coenzyme involved in a transaminase reaction is: A) biotin phosphate. B) lipoic acid. C) nicotinamide adenine dinucleotide phosphate (NADP+). D) pyridoxal phosphate (PLP). E) thiamine pyrophosphate (TPP). - ANS D 8. Transamination from alanine to alpha-ketoglutarate requires the coenzyme: A) biotin. B) NADH. C) No coenzyme is involved. D) pyridoxal phosphate (PLP). E) thiamine pyrophosphate (TPP). - ANS D 9. Which of the following reactions involving an amino acid cannot be catalyzed via a PLP-dependent mechanism? A) Hydrolysis B) Decarboxylation C) Racemization D) Transamination E) Transimination - ANS A 10. Which of the following is not true of the reaction catalyzed by glutamate dehydrogenase? A) It is similar to transamination in that it involves the coenzyme pyridoxal phosphate (PLP). B) NH4+ is produced. C) The enzyme can use either NAD+ or NADP+ as a cofactor. D) The enzyme is glutamate-specific, but the reaction is involved in oxidizing other amino acids. E) -Ketoglutarate is produced from an amino acid. - ANS A 11. Glutamate is metabolically converted to -ketoglutarate and NH4+ by a process described as: A) deamination. B) hydrolysis. C) oxidative deamination. D) reductive deamination. E) transamination. - ANS C 12. The conversion of glutamate to an alpha-ketoacid and NH4+: A) does not require any cofactors. B) is a reductive deamination. C) is accompanied by ATP hydrolysis catalyzed by the same enzyme. D) is catalyzed by glutamate dehydrogenase. E) requires ATP. - ANS D 13. Urea synthesis in mammals takes place primarily in tissues of the: A) brain. B) kidney. C) liver. D) skeletal muscle. E) small intestine. - ANS C 14. 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 - ANS D 15. 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 - ANS B 16. Conversion of ornithine to citrulline is a step in the synthesis of: A) aspartate. B) carnitine. C) pyruvate. D) tyrosine. E) urea. - ANS E 17. In the urea cycle, ornithine transcarbamoylase catalyzes: A) cleavage of urea to ammonia. B) formation of citrulline from ornithine and another reactant. C) formation of ornithine from citrulline and another reactant. D) formation of urea from arginine. E) transamination of arginine. - ANS B 18. Which of the following statements is false in reference to the mammalian synthesis of urea? A) Krebs was a major contributor to the elucidation of the pathway involved. B) The amino acid arginine is the immediate precursor to urea. C) The carbon atom of urea is derived from mitochondrial HCO3-. D) The precursor to one of the nitrogens of urea is aspartate. E) The process of urea production is an energy-yielding series of reactions. - ANS E 19. Which of the following amino acids are essential for humans? A) Alanine B) Aspartic acid C) Asparagine D) Serine E) Threonine - ANS E 20. 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) High carbohydrate, very low protein B) Very high carbohydrate, no protein, no fat C) Very very high fat, high carbohydrate, no protein D) Very high fat, very low protein E) Very low carbohydrate, very high protein - ANS E 21. Which of these amino acids can be directly converted into a citric acid cycle intermediate by transamination? A) Glutamic acid B) Serine C) Threonine D) Tyrosine E) Proline - ANS A 22. Which of these amino acids are both ketogenic and glucogenic? 1. Isoleucine 2. Valine 3. Histidine 4. Arginine 5. Tyrosine A) 1 and 5 B) 1, 3, and 5 C) 2 and 4 D) 2, 3, and 4 E) 2, 4, and 5 - ANS A 23. Tetrahydrofolate (THF) and its derivatives shuttle between different substrates. A) electrons B) H+ C) acyl groups D) one carbon units E) NH2 groups - ANS D 24. Which of the following is not a form of the most oxidized state of tetrahydrofolate (THF)? A) N10-formyl THF B) N5N10-methenyl THF C) N5N10-methylene THF D) N5-formyl THF E) N5-formimino THF - ANS C 25. The amino acids serine, alanine, and cysteine can be catabolized to yield: A) fumarate. B) pyruvate. C) succinate. D) alpha-ketoglutarate. E) None of the above - ANS B 26. 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. - ANS C 27. The human genetic disease phenylketonuria (PKU) can result from: A) deficiency of protein in the diet. B) inability to catabolize ketone bodies. C) inability to convert phenylalanine to tyrosine. D) inability to synthesize phenylalanine. E) production of enzymes containing no phenylalanine. - ANS C 28. In the human genetic disease maple syrup urine disease, the metabolic defect involves: A) a deficiency of the vitamin niacin. B) oxidative decarboxylation. C) synthesis of branched chain amino acids. D) transamination of an amino acid. E) uptake of branched chain amino acids into liver. - ANS B 29. Which of these amino acids are converted to alpha-ketoglutarate? 1. Glycine 2. Glutamate 3. Histidine 4. Arginine 5. Proline A) 1, 3, and 5 B) 2, 3, and 4 C) 2, 3, and 5 D) 2, 3, 4, and 5 E) 3, 4, and 5 - ANS D 30. Which of these amino acids are converted to succinyl CoA? 1. Isoleucine 2. Valine 3. Methionine 4. Arginine 5. Threonine A) 2 and 4 B) 2, 3, and 4 C) 2, 4, and 5 D) 1 and 5 E) 1, 3, and 5 - ANS E 31. Which of these amino acids are converted to oxaloacetate? 1. Asparagine 2. Glutamine 3. Serine 4. Arginine 5. Aspartate A) 2 and 4 B) 2, 3, and 4 C) 2, 4, and 5 D) 1 and 5 E) 1, 3, and 5 - ANS D