Final Exam Review UNE medical biochemistry questions and answers already passed

Final Exam Review UNE medical biochemistry questions and answers already passed Under fasting conditions (ratio of insulin: glucagon <1), elevated glucagon will activate which of the following enzymes? hormone sensitive lipase Ketonuria, hypoglycemia, and severe acidosis are prime diagnostic indicators of the presentation of type 1 diabetic ketoacidosis. Which of the following compounds are "ketone bodies" that would be elevated in serum of urine of a patient in this condition? D-3-hydroxybutyrate and acetoacetate What is the purpose of cholesterol esterification within the cell? (the conversion of cholesterol to cholesteryl ester) a. this modification makes cholesterol more soluble in the plasma membrane b. this modification does not change the chemical properties of cholesterol c. esterification is the first step in the synthesis of cortisol d. esterification traps cholesterol in the cell esterification traps cholesterol in the cell An individual goes to bed around 8 pm and doesn't wake up until 9 am the next morning. During this time, which of the following is the primary oxidizable substrate in the skeletal muscle? a. free fatty acids b. glycogen c. amino acids d. lactate free fatty acids A 22-year-old woman engaging in a political protest goes on a hunger strike on a prominent corner in a city park. She refuses all offers of food for except for water through the first 2 weeks. Under these conditions there is a decreased reliance on which of the following pathways for fuel? a. β-oxidation b. ketogenesis c. gluconeogenesis d. lipolysis gluconeogenesis 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? a. lipoprotein lipase b. cholesteryl ester transfer protein (CETP) c. lecithin cholesterol acyltransferase (LCAT) d. LDL receptor lecithin cholesterol acyltransferase (LCAT) A 16-year-old woman presents to her primary care physician for a follow up visit. At her initial visit, 3 months ago, her serum cholesterol was 255 mg/dL (above normal). She finds this very disappointing as she started a strict dietary regime reducing all fats and cholesterol, replacing them with a high carbohydrate diet. You tell her that high carbohydrate diets can increase serum triglyceride levels in some individuals. This can be attributed in an increase in the synthesis of which of the following lipoproteins? a. chylomicrons b. VLDL c. IDL d. HDL e. LDL VLDL a 5-year-old presents to her primary care physician. Her mother is concerned due to persistent diarrhea which is worse when eating fatty foods. The child also has some clinical signs of a deficiency in fat-soluble vitamins. Based on this information the child likely has a deficiency in the ability to synthesize which of the following lipoproteins? a. chylomicrons b. VLDLs c. LDLs d. HDLs chylomicrons The interaction of chylomicorns with lipoprotein lipase is stimulated by which of the following Apo proteins? a. ApoB 100 b. Apo B 48 c. Apo C II d. Apo E Apo C II A defect in the thioesterase subunit of fatty acid synthase would impair which of the following activities of the enzyme complex? a. liberation of newly assembled palmitate from the enzyme b. priming of the enzyme iwth acetyl-CoA c. Liberation of Co2 from 3-ketoacyl synthase d. binding of malonyl-CoA to an SH group liberation of newly assembled palmitate from the enzyme An increase in the ratio of insulin to glucagon leads to which of the following metabolic shifts? a. acetyl-CoA carboxylase will become dephosphorylated and active b. cytosolic levels of malonyl-CoA will decrease c. hormone sensitive lipase will become dephosphorylated and active d. VLDL synthesis will decrease acetyl-CoA carboxylase will become dephosphorylated and active HDL particles interact with VLDL particles to exchange cholesterol ester for triacylglyerols. Which of the following enzymes is responsible for this process? a. cholesterol ester transfer protein (CETP) b. LCAT (lecithin cholesterol acyltransferase) c. ABCA 1 trasnporter d. HMG CoA reductase cholesterol ester transfer protein (CETP) The LDL receptor is also highly regulated in the cell. Which of the following proteins targets the LDL receptor for degradation? a. proprotein convertase subtilisin/kexin type 9 (PSK9) b. Acyl-CoA: cholesterol acyltransferase (ACAT) c. Cholesterol esterase transfer protein (CETP) d. AMPK kinase PSK 9 Feedback: PSK9 is a regulator of LDL receptor recycling. IT targets the receptors for degradation rather than allowing them to be recycled to the cell surface. 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? a. malonyl-CoA b. acyl-CoA c. acetyl-CoA d. succinyl-CoA malonyl-CoA Secondary bile salts lack a hydroxyl group when compared to primary bile salts. What is the consequence of the loss of the OH group? a. secondary bile salts are more soluble b. secondary bile salts are more readily resorbed in the intestinal lumen c. the loss of the OH group does not change their functionality d. secondary bile salts are less soluble secondary bile salts are less soluble 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? a. have no change on solubility b. increase solubility c. decrease solubility decrease solubility The cellular uptake of LDL increases intracellular cholesterol levels. This has which of the following impacts on de novo cholesterol synthesis? increases degredation of HMG CoA reductase Which of the following enzymes is correctly paired with its allosteric inhibitor? Acetyl-CoA carboxylase; palmitoyl-CoA Which of the following is the regulated step of lipogenesis in eukaryotes? carboxylation of acetyl-CoA 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 Which of the following enzymes is correctly paired with its activator? N-acetylglutamate synthase; arginine Which of the followin genzymes is used directly in the synthesis of dTMP (thymidine) Thymidylate synthase 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? a. thioredoxin b. NADP+ c. Tetrahydrofolate d. NADH thioredoxin An elevation of purine nucleotides will negatively regulate pyrimidine synthesis through which of the following mechanisms? inhibiting the activity of carbamoyl phosphate synthetase II Folate is an essential compound in the synthesis of nucleotides. All of the following nucleotides require folate for synthesis except: CTP 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 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 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 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 In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPS II) can be allosterically activated by which of the following compounds? PRPP CPS II is the primary regulatory enzyme of pyrimidine synthesis. it is activated by PRPP and inhibited by UDP Which of the following reactions of the urea cycle takes place in the mitochondria? the synthesis of carbamoyl phosphate The urea cycle takes place in which of the following subcellular locations? the cytosol AND the mitochondria Which of the following non-essential amino acids is synthesized as part of the urea cycle? arginine 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 a deficiency in OTC is consisten with elevated orotic acid levels Your patient presents with a deficiency in the enzyme that catalyzes synthesis of N-acetylglutamate (NAGs). Which of the following would be a consequence of this deficiency? a. increased amino acids in the blood b. decreased digestion of dietary protein c. decreased excretion of uric acid d. increased glucose in the blood increased amino acids in the blood loss of the activator NAG will decrease urea cycle activity and lead to an increase of amino acids in the blood 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) An individual is suspected of having a deficiency in branched chain keto acid dehydrogenase (BCKAD). Supplementation of which of the following vitamins or cofactors may help resolve this issue? thiamine dehydrogenase enzymes (PDC, BCKAD, etc) require thiamine Which of the following statements is consistent with nitrogen transport in the fasted state? a. hepatic glutamate dehydrogenase will primarily produce glutamate b. transport of alanine from skeletal muscle will be reduced c. glutaminase will be inactive d. the urea cycle will be active the urea cycle will be active A plasma amino acid test in an infant with Maple syrup urine disease (MSUD) would show elevated levels of which of the following amino acids? a. arginine b. aspartic acid c. isoleucine d. lysine e. threonine isoleucine Alkaptonuira is a diagnosis of a deficiency in which of the following enzymes? homogentisate oxidase Which of the following enzymes is the regulatory step in the urea cycle? Carbamoyl phosphate synthetase I (CPS I) The reaction of ammonia with α-ketoglutarate is catalyzed by _________ and requires _________ as a reactant. glutamate dehydrogenase; NADH or NADPH glutamate dehydrogenase fixes ammonia to α-ketoglutarate and requires an energy donor Ubiquitination is a means of targeting a protein for which of the following cellular proceses? proteasomal degredation A deficiency in B6 (pyridoxal phosphate) would negatively impact which of the following pathways: 1. transsulfuration of homocysteine 2. remethylation of homocysteine 3. the folate cycle 1 only (metabolism of homocysteine to cysteine) phenylalanine to tyrosine requires BH4 methylation of malonyl-CoA to succinyl-CoA requires cobalamin Glucogenic amino acids that are used in the process of gluconeogenesis will be metabolized to all of the following compounds except: a. fumarate b. oxaloacetate c. succinyl-CoA d. Acetyl-CoA Acetyl-CoA Glucogenic AA are not oxidized to Acetyl-CoA. Acetyl-CoA is fully oxidized in the TCA cycle and therefore does not provide carbons to be used for gluconeogenesis 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? a. conversion of homocysteine to cysteine b. conversion of methyl malonyl-CoA to succinyl-CoA c. conversion of methionine to S-adenosyl homocysteine d. conversion of betaine to methionine Conversion of methyl malonyl-CoA to succinyl-CoA Which of the following compounds or substrates is required for the synthesis of tyrosine? (check all that apply) tetrahydrofolate (THF) tetrahydrobiopterin (BH4) Tryptophan Phenylalanine BH4 and Phenylalanine deficiency of BH4 would impair metabolism of phenylalanine to tyrosine and cause phenylketonuria