UNE Medical Biochemistry Midterm Review Already Graded A

UNE Medical Biochemistry Midterm Review Already Graded A A family presents for genetic counseling. The couple has two female children who are alive and well; however, their infant son recently died in the nursery with severe hemolysis (lysis of red blood cells) and jaundice. The wife recalls she lost a brother in infancy with severe hemolysis, induced after a viral infection. The physician suspects a glucose-6-phosphate dehydrogenase deficiency, this would result in a deficiency in which of the following compounds in red blood cells? Ribose and NADPH A patient presents to the emergency department with lactic acidosis. A deficiency in thiamine (TPP) is suspected and this will be consistent with a decrease in the activity of following enzymes? Transketolase Galactose 1-phosphate is initially converted to glucose 1-phosphate and requires which of the following compounds? UDP-Glucose Which of the following cofactors is required for transketolase activity? Thiamine diphosphate Aldolase B facilities a reaction that cleaves fructose 1-phosphate into two 3-carbon molecules that will enter glycolysis as which of the following compounds? Glyceraldehyde 3-phosphate High levels of activity of the non-oxidative portion of the pentose phosphate pathway will directly produce intermediates of which of the following pathways? Glycolysis The major regulatory step of the pentose phosphate pathway is catalyzed by which enzyme? Glucose 6-phosphate dehydrogenase Insulin stimulates fatty acid synthesis in the liver. These fatty acids are transported to the adipose tissue as which of the following? VLDL particles A young woman goes to work without eating breakfast and skips lunch. In this scenario, which of the following pathways is providing substrates used to generate ATP in the liver? Free fatty acids Caffeine is a natural inhibitor of phosphodiesterase. If you were to consume a large amount of coffee you would likely see a prolonged response to which of the following stimulants or hormones? Glucagon A teenage female presenting with lack of menstruation (amenorrhea) is found to have a dysfunctional steroid receptor characteristic of androgen insensitivity syndrome. Which of the following statements accurately describes steroid hormones? They enhance transcription when bound to receptors Steroid hormones bind which of the following types of receptors? Intracellular receptors Which of the following is a characteristic of all receptors? They are specific to a chemical messenger What is the primary oxidized fuel for skeletal muscle in the fasted state? Free fatty acids cAMP elicits multiple cellular responses. The effects of cAMP on gene transcription are directly mediated by which of the following DNA binding proteins? Cyclic-AMP response element binding protein (CREB) An individual is recently diagnosed with Type 2 diabetes. In this individual, hyperglycemia may in part be due to inactivity of which of the following glucose transporters on skeletal muscle? GLUT4 Glycogen degradation in the liver can be enhanced by elevated glucagon and the activation of a Gαs receptor. The initial step in this cascade involves which of the following second messengers or active enzymes? Adenylyl cyclase Which of the following combinations of compounds is required to fully activate pyruvate carboxylase (+ indicates compound is necessary; - indicates compound is not necessary)? 1. Biotin + Acetyl-CoA + Oxaloacetate + Malate - 2. Biotin + Acetyl-CoA + Oxaloacetate - Malate - 3. Biotin - Acetyl-CoA + Oxaloacetate + Malate + 4. Biotin - Acetyl-CoA - Oxaloacetate + Malate + 2 Which of the following compounds is not a substrate for gluconeogenesis? Acetyl-CoA A 1-month-old boy is brought to the emergency department in a coma after sleeping through the night and failing to awaken in the morning. He is given intravenous glucose and awakens. Serum levels of pyruvate, lactate, and alanine are elevated, whereas oxaloacetate and aspartate levels are reduced. Which of the following is the most likely diagnosis in this patient? Pyruvate carboxylase deficiency Which of the following would occur in the liver when glucose levels are high (think insulin is elevated)? Generation of glucose 1-phosphate to be used for glycogen synthesis Which of the following best describes the role of the Cori cycle? The process using lactate from skeletal muscle and red blood cells to generate glucose Which of the following compounds allosterically activates phosphofructokinase-1 (PFK1)? Fructose 2,6-bisphosphate Pyruvate dehydrogenase kinase catalyzes a reaction that results in which of the following? The phosphorylation and inactivation of E1 subunit of PDC (pyruvate dehydrogenase complex) Which of the following enzymes is correctly paired with its activator? Pyruvate dehydrogenase complex; pyruvate A farmer finds a cow dead in his field and notices an unusual plant nearby. Autopsy results show an elevated level of citrate present in the cow's mitochondria. This data collectively suggest inhibition of which of the following enzymes? Aconitase A 10-year-old girl is swimming in a local competition. The intense exercise will increase intracellular calcium levels which in turn will increase flux through the TCA cycle by stimulating the activity of all of the following enzymes EXCEPT? Succinate thiokinase Glycolysis provides intermediates that can be used to make other necessary substrates. One example of this is the direct conversion of pyruvate to which of the following amino acids? Alanine Pyruvate dehydrogenase complex is highly regulated. The enzyme will be most active when which of the following compounds is high? Pyruvate A newborn is determined to have hyperinsulinemia. Which of the following is likely to occur as a result of this deficiency? Increased activity of pyruvate kinase The glycerophosphate shuttle is the major shuttle of most tissues. Which of the following best describes the transfer of electrons by this shuttle? Electrons are directly transferred from glycerol 3-phosphate to an FAD containing glycerol phosphate dehydrogenase The fully reduced quinol form of CoQ contains which of the following combinations of electrons and protons? Two electrons and two protons A series of reactions have the following ΔG. A + B --> C ΔG = -1 C + D --> E ΔG = +3 E + F --> G ΔG = -5 The overall ΔG for this series of reactions is determined to be which of the following values? -3 As electrons flow through complexes in the inner mitochondrial membrane, protons are pumped from the matrix to the intermembrane space. Which of the following statements is most reflective of the pH in the intermembrane space? The pH is higher in the matrix when compared to the intermembrane space. Which of the following describes a correct and complete electron transfer pathway necessary for oxidative phosphorylation? NADH → complex I → CoQ → complex III → cyt c → complex IV Complex II (Succinate Q-reductase) is not considered to be part of the process of oxidative phosphorylation because it is unable to do which of the following activities? Pump protons from the mitochondrial matrix to the intermembrane space ATP is used to carry energy within the cell. The majority of energy in ATP is stored within which of the following bonds indicated on the image below? Which of the following components of the electron transport chain is not bound to the mitochondrial membrane? CoQ The malate-aspartate shuttle is used to move reducing equivalents of cytosolic NADH into the mitochondria where it can be oxidized. Which of the following compounds is used to move the reducing equivalents from cytosolic NADH into the mitochondria? Malate Succinate is a substrate for which complex in the electron transport chain? Complex II (Succinate-Q reductase) An enzyme is participating in a general acid-base catalysis reaction with an optimal reaction pH of 6.0. If acid is added to the environment reducing the pH to 3, what is the likely impact to the rate of reaction? The rate of the reaction is likely to decrease as the pH is out of optimal catalytic range If a mutation is made within the active site of an enzyme resulting in a decrease in Km, which of the following will be true with respect to the enzyme kinetics? The enzyme will require a lower substrate concentration to reach ½Vmax Which of the following is an example of enzyme regulation through covalent modification? Phosphorylation of muscle glycogen phosphorylase Which of the following best describes an enzyme inhibitor that increases the Km but does not change the Vmax? A competitive inhibitor The association of DNA and histones can be modified by histone acetylation. A decrease in histone acetylation will have which of the following impacts on the association of DNA and histones? Increase DNA: histone association Children with cystinosis have growth delay and both renal and ocular issues due to accumulation of cysteine in cellular lysosomes. The defect involves a specific lysosomal membrane receptor that facilitates cysteine removal from the cell. An effective therapy has been administration of a drug with a similar structure to cysteine. This therapy reflects the general principle that competitive inhibitors typically resemble the structure of which of the following? Substrates or ligands that bind the active site A new enzyme is discovered that increases in activity when it is phosphorylated on an exposed tyrosine residue. Phosphorylation of this amino acid is classified as which of the following? Covalent modification Cleavage of fructose 1, 6-bisphosphate to dihydroxyacetone and glyceraldehyde 3-phosphate is achieved by what class of enzymes? Lyase Changes in the physiological variables listed below can alter the affinity of hemoglobin for oxygen. Which of the following will lower the affinity of hemoglobin for oxygen? Increase in 2,3 bisphosphoglycerate (BPG) Prosthetic groups are complex nonprotein molecules that participate in catalysis by providing functional groups that form a covalent intermediate between the enzyme and the substrate. Which of the following is an example of a coenzyme or cofactor that participates in a covalent catalysis reaction? Pyridoxal phosphate An enzyme has a mutation within the substrate binding site that reduces the binding of the coenzyme needed for covalent catalysis. Which of the following is likely to result as a consequence of this mutation? The enzyme will not be able to form the transition state complex A 19-year-old boy is diagnosed with Creutzfeldt-Jakob Disease which is caused by the introduction of an amyloid fold in the disease-causing protein. The introduction of this fold causes the protein to transition from a primarily α-helical structure to an aggregate of mostly β-sheets. This change in protein structure (leading to disease) is best attributed to changes in which of the following? Folding of the secondary structures α-helices and β-sheets are primarily stabilized by which of the following interactions? Hydrogen bonding Chymotrypsin is a protease that cleaves peptide bonds. It is characterized as which of the following classes of enzymes? Hydrolases Covalent catalysis is used by many enzymes to cleave peptide bonds. Which of the following amino acids would not facilitate this type of catalysis? (Think of the structure of the R-group of these amino acids) Valine A 55-year old man is brought to the emergency room with a chief complaint of chest pain and tingling in his left arm. Elevation of which of the following enzymes in circulation would be most indicative of a myocardial infarction? Troponin Which of the following proteins is likely to have quaternary structure? A multimeric protein that contains multiple peptide chains Hemoglobin has the ability to display cooperative binding while myoglobin does not display this binding kinetic pattern. Which of the following differences between the two proteins accounts for this difference in binding kinetics? The presence of quaternary structure in hemoglobin Which of the following best describes the structure of heme? A planar porphyrin ring that binds iron Which amino acid would not be commonly found in the middle of an a-helical domain? Proline Which of the following best describes tertiary structure? Interactions between a-helices and B-sheets to form a domain Which of the following best describes a protein domain? A section of a protein structure sufficient to perform a particular chemical or physical task Under low energy conditions, AMP will bind to phosphofructokinase-1 and glycogen phosphorylase at a site unique to the active site. This enhances the activity of these enzymes. This is an example of which of the following types of enzyme regulation? Allosteric activation A new enzyme is discovered that increases in activity when phosphorylated on an exposed tyrosine residue. Phosphorylation of this amino acid is classified as which of the following? Covalent modification Which of the following is an example of enzyme regulation through covalent modification? Phosphorylation of muscle glycogen phosphorylase An example of enzyme activation by cleavage is best illustrated by which of the following? Activation of chymotrypsinogen to chymotrypsin Children with cystinosis have growth delayed both renal and ocular issues due to accumulation of cysteine in cellular lysosomes. The defect involves a specific lysosomal membrane receptor that facilitates cysteine removal from the cell. An effective therapy has been administration of a drug with a similar structure to cysteine. This therapy reflects the general principle that competitive inhibitors typically resemble the structure of which of the following? Substrates or ligands that bind the active site The association of DNA and histones can be modified by histone acetylation. A decrease in histone acetylation will have which of the following impacts on the association of DNA and histones? Increase DNA:histone association In the malate aspartate shuttle, glutamate is converted to ____________ in the mitochondria while aspartame is converted to _____________ in the cytosol. a-ketoglutarate; oxaloacetate As electrons flow through complexes in the inner mitochondrial membrane, protons are pumped from the matrix in the intermembrane spaces. Which of the following statements is most reflective of the pH in the intermembrane space? The pH is higher in the matrix when compared to the inter membrane space Which of the following statements is consistent with the actions of epinephrine? Epinephrine enhances glucose output from the liver under stressful conditions Which of the following pathways directly provides oxidizable substrate to red blood cells during the fasted state? Hepatic glycogenolysis Order the following statements to illustrate the correct cascade of events that occurs after ligand binding the G-protein coupled receptor (heptahelical receptor) 1. Degradation of cAMP by phosphodiesterase 2. Dissociation of GB + GY subunits 3. G protein exchanges GDP for GTP in the G-as subunit 4. Activation of adenylyl cyclase (effector E) to generate cAMP 3,2,4,1 Which of the following enzymes is responsible for the degradation of cAMP? Phosphodiesterase A suspected mutation in the cortisol receptor is discovered. Cortisol can still bind its receptor but the dimerized complex remains in the cytosol. Based on this description which region on the receptor is likely impacted? Nuclear localization signal Which of the following pathways provides the primary oxidizable fuel for skeletal muscle in the fasted state? Lipolysis from adipose tissue After a meal, fructose 2,6-bisphosphate levels are elevated. This compound will allosterically activate which of the following glycolytic compounds? Phosphofructokinase-1 (PFK-1) Which of the following best describes the net effect of the 8 steps of the TCA cycle? This process completely oxidizes an acetyl group to carbon dioxide Which of the following intermediates of the TCA cycle is required in the cytosol for fatty acid synthesis? Citrate In order for glucose to be retained within the cell, which of the following modifications must occur? Phosphorylation Certain metabolic conditions will reduce flux through the TCA cycle due to an increase in TCA cycle inhibitions. Elevation of which of the following would be an example of a compound that will reduce activity through the TCA? NADH Elevated levels of glucagon can enhance or inhibit many processes. Which of the following processes is not impacted by elevated levels of glucagon? Skeletal muscle glycogenolysis Which of the following events occurs during the formation of phosphoenolpyruvate from pyruvate during Gluconeogenesis? CO2 is required During an overnight fast, which of the following is the major source of blood glucose? Hepatic glycogenolysis When insulin levels are high, which of the following is true? Glycogen synthase is dephosphorylated and active In the non-oxidative portion of the pentose phosphate pathway, 2-carbon fragments of kept-sugars can be transferred to other sugars to generate a large sugar molecule. This reaction is catalyzed by which of the following enzymes? Transketolase An 18-month old is newly diagnosed with hereditary fructose intolerance (deficiency of Aldolase B). His mother reports he is particularly upset when he gets up in the morning or if he has not eaten in a while. Laboratory testing showed low blood glucose levels at the time of presentation. This presentation is likely due to an accumulation of fructose-1-phosphate and inhibition of which of the following pathways? Gluconeogenesis and glycogenolysis Which of the following enzymes is involved in the non-oxidative portion of the Pentose Pathway? Transaldolase