Biochemistry Exam Questions, Exams of Biochemistry

Download Biochemistry Exam Questions and more Exams Biochemistry in PDF only on Docsity! BMB 514 --- Exam II --- October 8, 2007 1A Name: __________________________________________ College: CHM COM (please print) (please circle) Please complete the following information on your Answer Sheet: (a) your name and signature (b) your student number (PID) (c) your college (in the area under SECTION): mark 001 for CHM student mark 002 for COM student (d) your version of the exam is 1A --- mark this in the area under FORM • There are 32 questions on this exam. For each question, mark the letter corresponding to what you consider is the BEST answer on the Answer Sheet provided. • When you leave the exam room, please turn in your Answer Sheet AND your exam to the proctors standing by the doors INSIDE the auditorium. Once you exit the auditorium, please leave the building. Hallway conversations disturb those still taking the exam. • There will be answer keys to this exam posted on the course website after the exam is completed. You may wish to copy your responses from your Answer Sheet onto the answer grid on the LAST page of this exam so that you can check your results. You can tear off the last page and take it with you. • You have 60 minutes to complete this exam. We will close the exam promptly at 8:30 a.m. Once we withdraw the boxes for the Answer Sheets from the doors, no additional Answer Sheets will be accepted. • Do well and good luck. 1) The conversion between malate and oxaloacetate plays an important role in the TCA cycle and gluconeogenesis. Which of the following statements best describes malate dehydrogenase, the enzyme that catalyzes this conversion? A) In the presence of high concentrations of NADH it favors the production of malate B) Inside the cell, it catalyzes an irreversible reaction C) It is only found in the mitochondria D) In the mitochondria, the production of oxaloacetate is favored during gluconeogenesis E) In the mitochondria the conversion of malate to oxaloacetate is a very favorable reaction (ΔGo’ <<0) 2) Which of the following CORRECTLY describes a step in the TCA cycle? A) Increased concentration of FADH2 will activate the succinate dehydrogenase enzyme B) The reaction catalyzed by succinate thiokinase produces one mole of GTP C) Citrate synthase is positively regulated by ATP D) Only two steps produce NADH E) Malate dehydrogenase is positively regulated by a high NADH/NAD+ ratio 3) In a red blood cell which of the following enzymes are required to produce NADPH and energy from glucose 6-phosphate? A) glucose-6-phosphate dehydrogenase, transketolase and glucokinase B) transaldolase, glucose 6-phosphate dehydrogenase, and hexokinase C) glucokinase, transaldolase, and phosphoglucose isomerase D) glucose 6-phosphate dehydrogenase, transaldolase and phosphofructokinase E) transaldolase, transketolase and glucokinase 4) Which of the following is NOT true about the structure of the mitochondria? A) Contains regulated uncoupler proteins in the inner membrane for heat production B) The outer membrane is permeable to ions and small proteins C) In a functional mitochondria, the intermembrane space has a low proton concentration D) The inner membrane contains a series of specialized transporters E) The mitochondrial matrix contains enzymes involved in the TCA cycle and fatty acid oxidation 5) The enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is involved in the energy transfer of the glycolytic pathway. Which of the following statements does NOT accurately describe GAPDH? A) Under anaerobic conditions it requires lactate dehydrogenase to supply NADH B) Contains a free sulfhydryl necessary to bind the substrate C) Produces a high energy intermediate that is used for substrate level phosphorylation D) Utilizes inorganic phosphate to produce 1,3-bisphosphoglycerate E) The substrate glyceraldehyde 3-phosphate is oxidized to form a high energy thioester 6) The synthesis of glycogen from glucose 6-phosphate can be CORRECTLY described by which of the following? A) Glycogenin is involved in creating 1,6-glycosidic bonds B) Requires no ATP C) Glucose 1-phosphate is first attached to uridine monophosphate via UTP D) Glycogen synthase is unphosphorylated in the presence of glucagon E) Branching enzyme creates 1,4 glycosidic linkages 17) Which of the following correctly describes the electron transport chain (ETC)? A) Inhibition of complex V stops the ETC due to build up of protons in the intermembrane space B) Coenzyme Q10 accepts electrons from complex II and Complex III C) Complex III is comprised of a TCA cycle enzyme D) Complex IV uses iron and cytochrome c as electron carriers E) All four complexes can transfer electrons and pump protons 18) Following the consumption of a high carbohydrate meal what following group of enzymes would you expect to be POSITIVELY regulated? A) pyruvate dehydrogenase, hexokinase, phosphofructokinase B) fructose 1,6-bisphosphatase, phosphofructokinase, hexokinase C) phosphoenolpyruvate carboxykinase, pyruvate kinase, pyruvate carboxylase D) glycogen phosphorylase, pyruvate dehydrogenase, glucokinase E) phosphofructokinase, phosphoenolpyruvate carboxykinase, glucokinase 19) Complex V (ATP synthase) is most accurately described by which of the following? A) Requires NAD+ to transfer protons across membrane B) Is comprised of two portions, one to allow proton flow and one to synthesize ATP C) Produced ATP is released directly into the cytoplasm D) Antimycin inhibits Complex V by stopping the flow of protons E) Its inhibition has no effect on mitochondrial oxygen consumption 20) A patient with a genetic defect in glucose-6-phosphate dehydrogenase wants to take a trip to Africa and is required to take mefloquine (an antimalarial drug) prior to obtaining her visa. Two nights after starting her mefloquine, she has a special meal of fava beans and liver. Soon after finishing the meal she collapses and is rushed into the emergency room where she is diagnosed with severe hemolytic anemia. All of the following are involved in her anemia EXECPT? A) The mefloquine is inhibiting her electron transport chain and she has run out of ATP B) Her inability to maintain NADPH within her RBCs following the oxidative stress of mefloquine and fava beans C) Her inability to maintain a pool of reduced glutathione because of the genetic defect and high oxidative power of the mefloquine and fava beans D) Her red blood cells cannot maintain membrane integrity under oxidative conditions 21) To produce the maximum ATP per mole of glucose consumed, the reducing power of the NADH produced by glyceraldehyde 3-phosphate dehydrogenase must make it into the mitochondria. Which of the following is NOT involved in shuttling these reducing equivalents via the malate-aspartate shuttle? A) an aspartate-glutamate shuttle B) a glutamate-oxaloacetate transaminase C) two copies of the malate dehydrogenase enzyme D) a malate-oxaloacetate transporter molecule C molecule A molecule D molecule B Reaction 1 Reaction 2 Reaction 3 [G] [H] [I] [J] [K] [L] Reaction 4 CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 C O SCoA CH3 [CH2]8 CH2 C O SCoAC H C H CH3 [CH2]8 CH2 C CH2 C O SCoA OH H CH3 [CH2]8 CH2 C CH2 C O SCoA O CH3 [CH2]8 CH2 O C SCoA CH3 O SCoAC molecule E molecule F + The following two questions (22-23) refer to the pathway drawn above. 22) Which of the following statements describing the above pathway is correct? A) The pathway oxidizes NADPH to NADP+ in reactions 1 and 3. B) The enzymes that carry out all 4 reactions are organized into a large complex. C) Insulin stimulates this pathway. D) The 4 reactions, respectively, are dehydrogenation, hydration, dehydrogenation, and cleavage. E) Citrate is the carrier of molecule A into the mitochondrial matrix. 23) Repeating reactions 1 through 4 will ultimately yield: A) Palmitate B) 8 acetyl CoA, 7 FADH2, 7 NADH + H+ C) 1 propionyl CoA, 6 acetyl CoA, 6 FADH2, 6 NADH + H+ D) 6 acetyl CoA, 6 FADH2, 6 NADH + H+ E) 1 propionyl CoA, 5 acetyl CoA, 5 FADH2, 5 NADH + H+ 24) A patient has a defective mitochondrial beta-ketothiolase enzyme. In this person’s skeletal muscle cells, which of the following pathways would be immediately affected? A) ketone body synthesis B) cholesterol synthesis C) beta-oxidation of fatty acids D) ketone body synthesis and beta-oxidation of fatty acids E) ketone body synthesis, cholesterol synthesis, and beta-oxidation of fatty acids 25) Linoleic acid and linolenic acid are essential fatty acids because A) They are precursors for palmitate. B) They are local hormones. C) They are omega-6 fatty acids. D) They have cis-double bonds beyond carbon 9. E) They are omega-3 fatty acids. 26) Which of the following statements regarding ketone body synthesis is false? A) Acetoacetate and beta-hydroxybutyrate are used as fuels by other tissues. B) Ketone bodies are hydrophobic and require a carrier for transport in the blood. C) Acetoacetate spontaneously decarboxylates because it is a beta-keto acid. D) Acetone is expired through the lungs. E) An intermediate of ketone body synthesis is formed from 3 molecules of acetyl CoA. 27) The process of fatty acid synthesis involves all of the following except: A) A large multi-enzyme complex B) Acetyl CoA carboxylase C) NADPH D) Malonyl CoA E) CAT I (carnitine acyl transferase I) 28) Dr. LaPres has decided to eliminate sugar from his diet for several days. Which of the following pathways would increase in his liver under these conditions? A) beta-oxidation, ketone body synthesis, and gluconeogenesis B) glycolysis and fatty acid synthesis C) ketone body synthesis and glycolysis D) gluconeogenesis and fatty acid synthesis E) glycolysis and beta-oxidation 29) The intermediate that serves as the key branch point between phosphosphingolipid and glycolipid synthesis is A) sphingosine B) ceramide C) phosphatidate D) arachidonate E) 1,2-diacylglycerol