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UNE BIOCHEMISTRY LATEST FINAL EXAM
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END OF PAGE Thyroid hormone is classified as a peptide hormone but it signals in a manner more closely related to which of the following hormones? A. cortisol B. Insulin C. epinephrine D. Growth hormone - ANSWERS-Cortisol Which of the following hormones will inhibit the release of growth hormone from the anterior pituitary? A. Insulin B. Growth hormone releasing factor C. Somatostatin
END OF PAGE D. Growth hormone - ANSWERS-Somatostatin Release of ACTH, from the pituitary, can be inhibited by which of the following hormones? A. Cortisol B. Insulin like growth factor C. Growth hormone D. Epinephrine - ANSWERS-Cortisol When cortisol is elevated which of the following processes is enhanced?
END OF PAGE The thyroid is unique as it can store thyroid hormone within the colloid space. Within the space the thyroid hormone is primarily stored in which of the following forms? - ANSWERS-As part of the thyroglobulin protein Which of the following processes does epinephrine enhance? - ANSWERS-Hepatic glycogenolysis Which two hormones bind intracellular receptors that can function as transcription factors? - ANSWERS-Cortisol and T In the absence of thyroid hormone, where is the thyroid hormone receptor located? - ANSWERS-Within the nucleus bound to DNA The catecholamines are part of the body's fight or flight response and will increase many different responses. Which of the following is not increased by release of catecholamines? - ANSWERS-Release of insulin Which of the following hormones signal through Tyrosine Receptor Kinase (TRK) receptors?
END OF PAGE A. aldosterone B. insulin C. thyroxin D. cortisol - ANSWERS-Insulin When levels of insulin are elevated which of the following processes is active? - ANSWERS-Skeletal muscle protein synthesis Within the pancreas, which of the following is a true statement with regards to the regulation of hormone release? - ANSWERS- Somatostatin inhibits the release of glucagon from alpha cells Exams can also be very stressful and elicit the release of cortisol. Cortisol will help maintain blood glucose levels, to supply your brain with glucose, by which of the following mechanisms - ANSWERS- Decreasing glucose uptake
END OF PAGE Which of the following compounds stimulates the synthesis of N- acetylglutamate? A. fumarate B. carbamoyl phosphate C. arginosuccinate D. arginine - ANSWERS-Arginine The pancreatic zymogen trypsinogen is activated by which of the following enzymes or compounds? A. Enteropeptidase B. HCO3- C. Trypsin
END OF PAGE D. H+ - ANSWERS-Enteropeptidase Which of the following is an insulin insensitive glucose transporter on the liver? - ANSWERS-GLUT Which of the following enzymes is the regulatory step in the urea cycle?
END OF PAGE 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? - ANSWERS-Alanine Which of the following enzymes is correctly paired with its activator? - ANSWERS-N-acetylglutamate synthatase; arginine The urea cycle takes place in which of the following subcellular locations? - ANSWERS-the cytosol and the mitochondria Which of the following enzymes is regulated by N-acetylglutamate (NAGs)? - ANSWERS-CPS I Which of the following enzymes is the regulatory step in the urea cycle?
END OF PAGE 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? - ANSWERS-Ornithine 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? - ANSWERS- Increased 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? - ANSWERS-Increases degradation of HMG-CoA reductase Dietary cholesterol is primarily transported in the body by which of the following lipoproteins? - ANSWERS-Chylomicron 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? - ANSWERS-Decrease solubility
END OF PAGE In the reaction catalyzed by cholesterol ester transfer protein (CETP), the VLDL particle receives which of the following compounds from HDL particles? - ANSWERS-Cholesterol-ester In reverse cholesterol transport HDL interacts with the ABCA transporter to move cholesterol from the cell to the HDL. This also requires the activity of which of the following enzyme? - ANSWERS- Lecithin 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? - ANSWERS-Cholesterol ester transfer protein (CETP) Which of the following is a major source of extracellular cholesterol for human tissues? - ANSWERS-LDLs 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? - ANSWERS- Thiamine
END OF PAGE 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? - ANSWERS-Cysteine Phenylketonuria can be caused by an enzymatic deficiency or it can present due to a deficiency in which of the following required metabolic cofactors? - ANSWERS-Tetrahydrobiopterin (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? - ANSWERS-Conversion 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? - ANSWERS-Tryptophan
END OF PAGE 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? - ANSWERS-Thioredoxin In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPSII) can be allosterically activated by which of the following compounds? - ANSWERS- 5 - phosphoribosyl 1-pyrophosphate (PRPP) Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)? - ANSWERS-Thymidylate 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? - ANSWERS-When 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? - ANSWERS- Orotate phosphoribosyltransferase
END OF PAGE The transamination of all amino acids requires which of the following cofactors? - ANSWERS-Pyridoxal phosphate (PLP) Ubiquitination is a means of targeting a protein for which of the following cellular processes? - ANSWERS-Proteasomal degradation Which of the following reactions of the urea cycle takes place in the mitochondria? - ANSWERS-The 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. Which of the following amino acids has a nitrogen in its side chain and is an intermediate of the urea cycle? - ANSWERS-Arginine 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? - ANSWERS-Loss of function of cystathionine-β synthase
END OF PAGE 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? - ANSWERS-PRPP (5- phosphoribosylpyrophosphate) 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? - ANSWERS- Xanthine oxidase In the salvage of purines, hypoxanthine-guanine phosphoribosyl transferase (HGPRT) is responsible for which of the following processes? - ANSWERS-Conversion of guanine to guanosine monophosphate (GMP) In the case of a deficiency of biotin, which of the following enzymes required for fatty acid metabolism will be impaired? - ANSWERS- 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? - ANSWERS-Malonyl-CoA
END OF PAGE 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) - ANSWERS- 4 A 2 - day-old infant test positive for hyperphenylalaninemia. This is most likely caused by a heritable defect in which of the following enzymes? - ANSWERS-Phenylalanine hydroxylase 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? - ANSWERS-Tyrosine In pyrimidine synthesis, uridine triphosphate (UTP) can feedback and inhibit which of the following enzymes? - ANSWERS-Carbamoyl phosphate synthase II Which of the following characteristics distinguish most RNA molecules from DNA? - ANSWERS-Uridine base on RNA, whereas a thymidine base on DNA
