Dental Students Biochemistry Exam V Questions - 2006 ( Note: In all cases, the only correct answer is the best answer) 1. Essential fatty acids are: A. precursors of biotin B. precursors of tyrosine C. precursors of prostaglandins D. precursors of coenzyme A E. precursors of riboflavin 2. Regulation of fatty acid biosynthesis occurs: A. when carnitine oxidizes acetyl-coa B. when acetyl-coa carboxylase is phosphorylated and dephosphorylated C. when biotin binds to and inactivates acetyl-coa-carboxylase D. when glucagon stimulates dehydration of the alpha beta double bond 3. This reversible reaction is pulled in one direction for fatty acid oxidation and in the other direction for fatty acid biosynthesis. Identify the one reaction. A. amination, deamination B. carboxylation, decarboxylation C. phosphorylation, dephosphorylation D. hydration, dehydration 4. This amino acid is used to biosynthesize phosphoglycerides and cysteine: A. serine B. glycine C. arginine D. taurine E. carnitinine 1
5. The two coenzymes that are utilized to metabolize propionate to succinate are: A. NAD, biotin B. B 6, biotin C. B 12, NAD D. biotin,b 12 6. Omega 3 fatty acids, in fish oils: A. are metabolized similar to cholesterol B. are metabolized similarly to archidonic acid, and replace arachidonic acid in phosphoglyerides C. are not digestable D. are linked to acidic peptides 7. Transport of dietary triglycerides is via the (a) particle while transport of triglycerides made in the liver is via the (b) Particle. A. (a) serum albumin (b) LDL B. (a) LDL (b) chylomicon C. (a) chylomicron (b) VLDL D. (a) VLDL (b) chylomicron E. (a) LDL (b) VLDL 8. Gangliosides are formed from a: A. ceramide plus carnitine B. ceramide plus taurine C. cerebroside plus glycine D. ceramide plus oligosaccharides with acidic sugars 2
9. The regulated step in cholesterol biosynthesis is: A. acetyl-coa carboxylase B. propionyl-coa carboxylase C. hydroxymethylglutaryl-coa reductase D. PRPP synthetase E. carnitine deaminase 10. The five-carbon building block used to make cholesterol is: A. ceramide B. glutamine C. CTP D. inositol E. isopentenyl-pyrophosphate 11. The three drugs or types of drugs which block cholesterol biosynthesis, block VLDL synthesis and secretion and sequester a major metabolite of cholesterol are: A. biotin: riboflavin; bile acid binders B. statins; biotin; lysolecithin C. statins; nicotinic acid; bile acid binders D. statins; pantothenic acid; hydrochloric acid binders E. biotin; pantothenic acid; lysolecithin 12. The oxidation of a polyunsaturated fatty acid involves two steps in addition to all the steps for the oxidation of saturated fatty acid. The two additional steps are: A. isomerization; oxidation B. carboxylation; oxidation C. methylation; reduction D. reduction; carboxylation E. reduction; isomerization 3
13. Which of the following amino acids can all be directly converted to α ketoglutarate? A. proline, lysine, alanine B proline, glutamic acid, histidine C. histidine, glycine, cysteine D. alanine, valine, methionine E. methionine, arginine, serine 14. The amino acids that all belong to the family involved in one carbon metabolism are: A. lysine, glycine,alanie B. methionine, isoleucine, leucine C. tryptophan, phenylalanine, tyrosine D. histidine, serine, methionine E. aspartic acid, asparaine, glutamine 15. The following amino acid is metabolized to an iodinated hormone and also to bioactive compounds called catecholamines. (select one correct answer) A. guanine B. methionine C. cysteine D. arginine E. tyrosine 16. The direct metabolic origin of the two nitrogens (N) and one carbon of urea is: A. the amide N of glutamine, CO 2 (or HCO 3 ), the epsilon N of lysine B. the amino N of histidine, ammonia and CO 2 (or HCO 3 ) C. the amino N of aspartate, ammonia and CO 2 (or HCO 3 ) D. the amide N of asparagine, the amino group of aspartic acid and formic acid E. the amino N of alanine acid, the amino N of arginine and CO 2 (or HCO 3 ) 4
17. The other substrate used by phosphoribosyl transferases to form IMP from hypoxanthine, to form AMP from adenine and to form OMP from orotic acid is: A. glutamine (GluNH 2 ) B. aspartic acid (Asp) C. carbamoyl phosphate D. phosphoribosyl-pyrophosphate (PRPP) E. glycine 18. The carbons and nitrogen(s) of this amino acid are directly used in the synthesis of the purine ring skeleton: (select one correct answer) A. aspartate B. glutamic acid C. glutamine D. alanine E. glycine 19. After the old red blood cell with its heme molecule is engulfed by phagocytes of the reticuloendothelial system, the: A. iron is excreted and the protoporphyrin recycled B. billirubin is converted to new heme by these cells C. the porphyrin ring is metabolized to δ aminolevulinate D. iron is recycled to new heme and the porphyrin ring catabolized to billirubin E. the phagocyte delivers the damaged red blood cell to the bone marrow to be repaired 20. The unique folate dependent enzyme that catalyzes the transfer of a one carbon moiety and the concerted reduction of the oxidation state of that one carbon moiety is: A. thymidylate synthase B. AICAR transformylase C. aspartate transcarbamoylase D. dihydrofolate reductase E. Hypoxanthine Guanine Phosphoribosyl Transferase (HGRPT) 5
21. These two enzymes act as a ph and ammonia buffering system: (select the one correct answer) A. glutamine synthetase, glutaminase B. methylmalonyl CoA mutase, dihydrofolate reductase C. carbamoyl phosphate synthetase, AICAR transformylase D. adenosine deaminase, purine nucleoside phosphorylase E. glutamic pyruvate transaminase, adenosine deaminase 22. In vivo, this enzyme catalyzes the formation of glycine and is a major supplier of one carbon fragments carried by tetrahydrofolate coenzymes. Identify the correct substrate and the name for this enzyme: A. homocysteine, methionine synthase B. dump, thymidylate synthase C. serine, serine hydroxymethyl transferase D. valine, branched chain keto acid dehydrogenase E. creatinine, creatine kinase 23. The amino acid used to make pyrimidines is A. Alanine B. Aspartic Acid C. Arginine D. Adenosine E. Ornithine 24. The form(s) of tetrahydrofolate (THF) that are used to make purines and pyrimidines are (a) and the form(s) that are trapped in B 12 deficiency are (b) A. (a) 5-methy-THF b. 5-formyl-THF B. (a) 10-formyl THF, 5, 10 methylene THF (b) 5-methyl THF C. (a) 5-formyl-THF, 5-methyl-THF (b)10-formyl-thf, THF D. (a) 5-methyl-THF (b) THF 6
25. The transamination reaction requires the following coenzyme(s) A. B 12, Biotin B. Thiamine pyrophosphate C. Pyridoxal phosphate (B 6 ) D. FAD E. NAD 26. A defective hydroxylation enzyme causes this inborn error in metabolism (a) and, in this individual, this amino acid is essential (b) A. (a) Phenylketonuria (PKU) (b) tyrosine B. (a) Carbamoylphosphate synthetase (b) urea C. (a) Homocysteinuria (b) glycine D. (a) aspartate transaminase (b) histidine 27. Lack of feedback inhibition of this enzyme (a) by nucleotides due to a defective enzyme (b) causes this syndrome (c) A. (a) Cystathionine synthase (b) HGPRT (c) homocysteinuria B. (a) Aspartate transcarbamoylase (b) adenosine deaminase (c) gout C. (a) PRPP amido transferase (b) HGPRT (c) Lesch Nyhan 28. The major metabolic fuel for the liver is A. glucose B. fatty acids C. ketone bodies D. α-keto acids E. NADPH 7
29. What effect does vigorous exercise have on the catabolism of ingested alcohol? A. no effect B. decreases the rate of alcohol breakdown C. increases the rate of alcohol breakdown D. leads to the synthesis of long chain alcohols 30. A major source of energy for an athlete running a marathon is A. creatine phosphate B. anaerobic glycolysis C. ketone bodies D. fatty acids E. stored muscle ATP 31. The activation of protein kinase A is an example of A. allosteric activation B. hormonal activation by reversible phosphorylation C. hormonal activation acting through a modulator protein D. post-translational modification 32. The regulation of the activity of what enzyme is most important for controlling the rate of glycolysis? A. glucose-6-phosphatase B. hexokinase C. pyruvate kinase D. glyceraldehyde-3-phosphate dehydrogenase E. phosphofructokinase 8
33. What step in a complex biochemical pathway is usually highly regulated? A. the last step that yields the final product of the pathway B. the first committed step in the pathway that yields the final product. C. the step catalyzed by a monomeric enzyme D. the second step in the pathway E. the step that utilizes ATP 9
Dental Biochemistry Exam V (Key) 1. C 2. B 3. D 4. A 5. D 6. B 7. C 8. D 9. C 10. E 11. C 12. E 13. B 14. D 15. E 16. C 17. D 18. E 19. D 20. A 21. A 22. C 23. B 24. B 25. C 26. A 27 C 28. D 29. B 30. D 31. C 32. E 33. B 10