UNE BioChem unit 4 multiple choice questions with certified answers

UNE BioChem unit 4 multiple choice questions with certified answers Which of the following non-essential amino acids is synthesized as part of the urea cycle? Arginine Which of the following reactions of the urea cycle takes place in the mitochondria? The synthesis of carbamoyl phosphate The transamination of all amino acids requires which of the following cofactors? Pyridoxal phosphate (PLP) A comatose infant is brought to the ER. In the course of the examination, plasma ammonia was found to be elevated 20-fold over normal values. Urine orotic acid and uracil were both greater than normal. A defect of which of the following enzymes is the most likely diagnosis? Ornithine transcarbamoylase Which of the following enzymes is likely to be active in both the fed and fasted states? Glutaminase The reaction of ammonia with α-ketoglutarate is catalyzed by _________ and requires _________ as a reactant. Glutamate dehydrogenase; NADH or NADPH Which of the following enzymes is regulated by N-acetylglutamate (NAGs)? Carbamoyl phosphate synthetase I (CPS I) Your patient presents with a deficiency of the enzyme that catalyzes synthesis of N-acetylglutamate (NAGs). Which of the following would be a consequence of this deficiency in the patient? Increased amino acids in the blood Homocystinuria can be caused by several different enzyme or vitamin deficiencies. An elevation of homocysteine and a decrease in cysteine would most likely present due to which of the following deficiencies? Loss of function of cystathionine-β synthase A 15-year-old female presents to her pediatrician with concerns over her inability to sleep, increased feelings of depression and generalized fatigue. A full laboratory work-up is ordered and based on these findings she is diagnosed with a melatonin deficiency. Based on this information, metabolism of which of the following amino acids is likely impaired? Tryptophan In an individual with a deficiency in the branched chain ketoacid dehydrogenase complex, metabolism of which of the following amino acids would not likely be impaired? Tyrosine A 52-year- old male sought medical help complaining about progressive appearance of hyperchromic (hyper pigmented) papules on the edge of the second finger of both hands. He also complained about darkening of urine. Incisional biopsy of one of the spots on his hands and urine sample tested positive for or homogentisic acid. Based on these findings a diagnosis of alkaptonuria is made. This diagnosis is consistent with a deficiency in which of the following enzymes? Homogentisate oxidase Which of the following compounds or substrates is required for the synthesis of tyrosine? (+ indicates the compound is required; - indicates the compound is not required) (THF) (BH4) Tryptophan Phenylalanine 1. + + + - 2. - + + - 3. + - - + 4. - + - + 4 An individual is suspected of having a deficiency in branched chain keto acid dehydrogenase. Supplementation of which of the following vitamins or cofactors may help resolve this issue? Thiamine A 2-day-old infant test positive for hyperphenylalaninemia. This is most likely caused by a heritable defect in which of the following enzymes? Phenylalanine hydroxylase A deficiency in B6 (pyridoxal phosphate) would negatively impact which of the following pathways: 1. Metabolism of homocysteine to cysteine 2. Metabolism of phenylalanine to tyrosine 3. Conversion of methyl malonyl-CoA to succinyl-CoA 1 only The ribonucleotide reductase is important for converting ribose bases to the deoxy form. This conversion is coupled with the oxidation of which of the following compounds? Thioredoxin A patient recently diagnosed with colon cancer is being treated with 5-fluorouracil. Which of the following enzymes will this drug directly inhibit? Thymidylate synthase Purine biosynthesis starts with the activation of a 5-carbon sugar. In this initial reaction, ribose 5-phosphate is converted into which of the following compounds? PRPP (5- phosphoribosylpyrophosphate) In the salvage of purines, hypoxanthine-guanine phosphoribosyl transferase (HGPRT) is responsible for which of the following processes? Conversion of guanine to guanosine monophosphate (GMP) A 4-year-old girl presented to the clinic with megaloblastic anemia and failure to thrive. Urinalysis showed significant sediment with extremely high levels of orotic acid. A deficiency in which of the following enzymes would be consistent with this presentation? Orotate phosphoribosyltransferase Which of the following characteristics distinguish most RNA molecules from DNA? Uridine base on RNA, whereas a thymidine base on DNA A 40-year-old male comes in to the doctor's office with severe pain in his big toe. He is diagnosed with gout. Allopurinol is administered and this drug will inhibit which of the following enzymes? Xanthine oxidase Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)? Thymidylate synthase Which of the following enzymes is likely to be active in both the FED and FASTED states? glutaminase A 52 year old male sought medical help complaining bout progressive appearance of hyperchromic papules on the edge of the second finger of both hands. He also complained about darkening of urine. INcisional biopsy of one of the spots on his hand and urine sample tested positivie for homogentisic acid. Based on these findings, a diagnosis of alkaptonuria is made. This diagnosis is consistenet with a deficiency in which of the following enzymes? homogentisate oxidase `An elevation of purine nucleotides will negatively regulate pyrimidine synthesis through which of the following mechanisms? inhibiting the activity of carbamoyl phosphate synthetase II Methotrexate is a potent anticancer agent that starves dividing cells of deoxyribonucleotides through direct inhibition of which of the following processes? Metabolism of folic acid The glucose-alanine cycle is a method of transferring ammonia from the skeletal muscle to the liver. In this process the non-toxic carrier of ammonia is which of the following compounds? alanine Which of the following enzymes is correctly paired with its activator? N-acetylglutamate synthatase; arginine The urea cycle takes place in which of the following subcellular locations? the cytosol and the mitochondria Which of the following enzymes is the regulatory step in the urea cycle? Carbamoyl phosphate synthetase I (CPS I) Which of the following statements is consistent with nitrogen transport in the fasted state? The urea cycle will be active Phenylketonuria can be caused by an enzymatic deficiency or it can present due to a deficiency in which of the following required metabolic cofactors? (BH4) A 55-year old man presents to his primary care physician with bouts of dizziness and confusion. He is diagnosed with hyperhomocysteinemia due to a deficiency of cystathionine-ß synthase. In this individual which of the following amino acids could potentially become essential? Cysteine A 17-year old female presents to her primary care and is diagnosed with a Vitamin B12 (cobalamin) deficiency. In this individual, which of the following reactions would be compromised? Conversion of methyl malonyl-Co A to succinyl-CoA A 47-year-old man complains of pain in the joints of his left big toe, which are obviously swollen and tender. The pain has been chronic but became intolerable the day after Thanksgiving when he had a large meal and several glasses of red wine. Based on this information a diagnosis of gout is made. Which of the following is involved in the pathophysiology of this patient's condition? Elevated uric acid Which of the following is the common intermediate for purine synthesis? Inosine monophosphate In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPSII) can be allosterically activated by which of the following compounds? PRPP The regulation of PRPP synthetase is critical in the production of both purines and pyrimidines. This enzyme is inhibited under which of the following conditions? When both GDP and ADP are elevated Ubiquitination is a means of targeting a protein for which of the following cellular processes? Proteasomal degradation Several amino acids are intermediates of the urea cycle, having side ammonia groups that join with free carbon dioxide (CO2) and ammonia to produce net excretion of ammonia as urea. Which of the following amino acids has a nitrogen in its side chain and is an intermediate of the urea cycle? Arginine S-adenosylmethionine (SAM) is synthesized from ATP and methionine. A deficiency in which of the following enzymes would impair the production of SAM? Methionine adenosyltransferase (MAT) The conversion of ribose bases into deoxy-bases will be occurring under which of the following conditions? When cells are proliferating In the case of a deficiency of biotin, which of the following enzymes required for fatty acid metabolism will be impaired? Acetyl-CoA carboxylase During fatty acid synthesis, after the initial step involving acetyl-CoA, the fatty acid chain is elongated by the addition of which of the following compounds? Malonyl-CoA You and a friend are being chased by a bear. Under these conditions levels of epinephrine are increased due to metabolism of which of the following amino acids? Tyrosine In pyrimidine synthesis, uridine triphosphate (UTP) can feedback and inhibit which of the following enzymes? Carbamoyl phosphate synthase II Increase in ethanol consumption leads to an increase in the ratio of NADH/NAD+. This promotes the conversion of pyruvate to which fo the following compounds? Lactate The oxidation of ethanol increases the ratio of NADH/ NAD in both the mitochondria and the cytosol. This leads to the inhibition of which of the following enzymes in the TCA cycle? Isocitrate dehydrogenase Several friends went out Saturday evening to celebrate an exam. They skipped dinner and decided to head straight to the bar. The next morning one of the individuals was found laying unconscious at the bottom of the stairs. He was rushed to the emergency department and blood glucose levels of 30mg/ dL (normal range 100-120mg/ dL). At the time of presentation, which of the following would be consistent with this individuals signs and symptoms (when compared to a normal individual)? Increase lactate levels Which will not increase orotic acid? NAG Which of the following is the primary role of glutaminase in the liver? To free an amine group from glutamine A newborn infant was resuscitated at birth and was found to be neurologically compromised, with marked flaccidity (lack of muscle tone), and cardiac insufficiency. Glutamine was largely absent from the serum and ammonia levels were excessively elevated and urea production was otherwise not impaired. Based on this information which of the following enzymes is likely deficient in this infant? Glutamine synthetase Which of the following amino acids is essential? Methionine An infant is normal at birth but becomes lethargic after several feedings. The assigned nurse describes an unusual smell to the urine but is ignored. Infection (sepsis) is suspected, and blood tests show normal white blood cell counts with a serum pH of 7.0. Evaluation for an inborn error of metabolism shows an abnormal amino acid screen. The report states that branch-chain amino acids are strikingly elevated. Elevation of which of the following amino acids would be consistent with the report? Isoleucine Glucogenic amino acids that are used used in the process of gluconeogenesis and will be metabolized to all of the following compounds except: Acetyl-CoA Folate is an essential compound in the synthesis of nucleotides. All of the following nucleotides require folate for synthesis except: CTP