UNE Biochemistry Final Exam Review Questions With 100% Correct Answers

UNE Biochemistry Final Exam Review Questions With 100% Correct Answers 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? - answerOrnithine transcarbamoylase 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? - answerIncreased amino acids in the blood The cellular uptake of LDL increases intracellular cholesterol levels. This has which of the following impacts on de novo cholesterol synthesis? - answerIncreases degradation of HMG-CoA reductase Dietary cholesterol is primarily transported in the body by which of the following lipoproteins? - answerChylomicron Secondary bile salts are generated by bacterial modification of primary bile salts in the intestinal lumen. These modifications have which of the following impacts on bile salt solubility? - answerDecrease solubility A 47-year-old male is prescribed a statin (HMG-CoA reductase inhibitor) to manage his elevated LDL cholesterol. What is the initial mechanism of action for obtaining the desired effect in this man? - answerDecreasing hepatic cholesterol biosynthesis A deficiency in the LDL receptor will result in an initial decrease in which of the following? - answerIntracellular cholesterol A 45-year-old man has a mild heart attack and a history of vascular disease. He is placed on a Mediterranean diet and statin drug therapy. Which of the following will be the most likely result of this drug therapy? - answerLow blood LDLs A 45-year-old man is found to have an elevated serum triglycerides of > 730mg/dL. He tells you he forgot to fast before his visit and he ate a full breakfast of bacon and eggs before the labs were drawn. Which of the following lipoproteins would be the largest contributors to a measurement of plasma triglycerides in this situation? - answerChylomicrons and VLDLs In the reaction catalyzed by cholesterol ester transfer protein (CETP), the VLDL particle receives which of the following compounds from HDL particles? - answerCholesterol-ester In reverse cholesterol transport HDL interacts with the ABCA1 transporter to move cholesterol from the cell to the HDL. This also requires the activity of which of the following enzyme? - answerLecithin cholesterol acyltransferase (LCAT) HDL particles interact with VLDL particles to exchange cholesterol ester for triacylglyerols. Which of the following enzymes is responsible for this process? - answerCholesterol ester transfer protein (CETP) Which of the following is a major source of extracellular cholesterol for human tissues? - answerLDLs 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? - answerThiamine 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? - answerCysteine Phenylketonuria can be caused by an enzymatic deficiency or it can present due to a deficiency in which of the following required metabolic cofactors? - answerTetrahydrobiopterin (BH4) 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? - answerConversion of methyl malonyl-Co A to succinyl-CoA 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? - answerTryptophan 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? - answerHomogentisate oxidase Methotrexate is a potent anticancer agent that starves dividing cells of deoxyribonucleotides through direct inhibition of which of the following processes? - answerMetabolism of folic acid 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? - answerElevated uric acid Which of the following is the common intermediate for purine synthesis? - answerInosine monophosphate 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? - answerThioredoxin In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPSII) can be allosterically activated by which of the following compounds? - answer5-phosphoribosyl 1- pyrophosphate (PRPP) Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)? - answerThymidylate synthase 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? - answerWhen both GDP and ADP are elevated 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? - answerOrotate phosphoribosyltransferase The transamination of all amino acids requires which of the following cofactors? - answerPyridoxal phosphate (PLP) Ubiquitination is a means of targeting a protein for which of the following cellular processes? - answerProteasomal degradation Which of the following reactions of the urea cycle takes place in the mitochondria? - answerThe synthesis of carbamoyl phosphate 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.