Assessment Exam:Biochemistry

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1. Which statement is correct concerning the T (deoxy) and R(oxy) states of tetrameric hemoglobin?
   A. in the T to R transition, the central cavity of the tetramer decreases in size, preventing the binding of the allosteric modulator, 2,3-bisphosphoglycerate
   B. the R form involves interchain salt links that are broken in transition to the T form
   C. in the T to R transition, the position of several helices change, but the position of the iron atom in heme remains fixed
   D. in the Bohr effect, lowering pH preferentially stabilizes the R form and enhances oxygen binding
   E. none of the statements are correct
   


2. Cleavage of disulfide bonds in globular proteins may be brought about by
   A. reaction with fluoro-2,4-dinitrobenze (FDNB) at pH 5.0
   B. reaction with diisopropylfluorophosphate (DIFP) at pH 7.0
   C. incubation at pH 4.0 in the absence of oxygen
   D. reaction with b-mercaptoethanol at pH 8.0 in 8M urea
   E. digestion with trypsin
   


3. The carnitine derivatives of long chain fatty acids are used
   A. to transport fatty acids from the plasma membrane to the mitochondia
   B. to transport acetate units out of the mitochondria
   C. as complexes of fatty acids during fatty acid synthesis
   D. as complexes of fatty acids during fatty acid degradation
   E. to transport long chain fatty acids across the mitochondrial membrane
   


4. A technique that is widely used to amplify DNA sequences is
   A. polymerase chain reaction
   B. replica plating
   C. Southern blotting
   D. genomic walking
   E. directional cloning
   


5. After the respiratory inhibitor, cyanide (CN^-), is added to a suspension of actively respiring, tightly coupled, mitochondria
   A. the rate of mitochondrial ATP synthesis will increase
   B. the rate of oxygen consumption will decrease
   C. the P/O ratio will approach a value of 2.5
   D. ubiquinone will become more reduced and cytochrome c will become more oxidized
   E. the inner membrane will become permeable to ATP
   


6. Which metabolic process requires a "branching" enzyme?
   A. gluconeogenesis
   B. glycolysis
   C. glycogen synthesis
   D. glycogenolysis (glycogen degradation)
   E. Calvin cycle
   


7. The pentose phosphate pathway (also called the phosphogluconate pathway) is active in animal cells that synthesize fatty acids and steroids. The pentose phosphate pathway
   A. can catabolize glucose but not glucose-6-phosphate
   B. produces ribose-5-phosphate that is used in fatty acid synthesis
   C. is maximally active, relative to glycolysis, when the cellular ATP to ADP ratio is very low
   D. produces NADPH that is used as a reducing agent in anabolic pathways
   E. is also the main pathway for the oxidative degradation of serine and isoleucine
   


8. Malonic acid is a competitive inhibitor of succinate dehydrogenase. Suppose you add an amount of malonic acid that completely inhibits succinate dehydrogenase but effects no other cellular functions. How many high-energy nucleoside triphosphates would be generated by the aerobic conversion of one molecule of pyruvate to products assuming this amount of malonic acid is present? (assume a P/O ratio of 2.5)
   A. 2.5
   B. 5.0
   C. 7.5
   D. 8.5
   E. 10.0
   


9. According to the simplest version of the chemiosmotic coupling hypothesis, ATP synthesis in mitochondria is coupled directly to
   A. the flavin-linked oxidation of coenzyme Q
   B. the extrusion of water from the mitochondrial matrix across the inner membrane
   C. the spontaneous exchange of K⁺ for Na⁺ across the outer mitochondrial membrane
   D. the movement of protons across the inner mitochondrial membrane into the matrix
   E. the exergonic efflux of ADP across the outer mitochondrial membrane into the cytoplasmism
   


10. Reverse transcriptase is an enzyme that synthesizes
    A. RNA using DNA as a template
    B. RNA using RNA as a template
    C. DNA using RNA as a template
    D. DNA using protein as a template
    E. RNA using protein as a template
    


11. DNA polymerase synthesizes DNA in what direction?
    A. 2^' to 3^'
    B. 3^' to 5^'
    C. 5^' to 3^'
    D. 3^' to 2^'
    E. two of these are correct
    


12. Which characteristic of the B form of DNA is incorrect?
    A. adjacent nucleotides in the same strand are covalently joined by phosphodiester linkages
    B. the two DNA strands have opposite polarities with respect to backbone orientation
    C. the sugar-phosphate backbone is oriented toward the outside of the helix
    D. the base pairs are stacked over one another inside the helix
    E. the helical twist is opposite to that in the A-form of DNA
    


13. Acetyl CoA is important because it is
    A. the form in which fatty acids enter the citric acid cycle
    B. a form in which carbohydrates enter the citric acid cycle
    C. a key intermediate in the conversion of carbohydrates to fats
    D. a form in which amino acids enter the citric acid cycle
    E. all of these things
    


14. Dialysis would be most useful for the separation of
    A. ATP from ADP
    B. DNA from protein
    C. glucose from lactose
    D. ammonium sulfate from an enzyme
    E. hydrophobic amino acids from hydrophilic amino acids
    


15. An inhibitor that increases K_m and does not alter the V_max value is
    A. a competitive inhibitor
    B. an irreversible inhibitor
    C. a non-competitive inhibitor
    D. an uncompetitive inhibitor
    E. a suicide inhibitor
    


16. The sigma factor (s) that is associated with bacterial RNA polymerase is necessary to
    A. correctly initiate RNA synthesis at promoter regions
    B. correctly terminate RNA synthesis
    C. enhance the rate of chain elongation after initiation of RNA synthesis is over
    D. recognizes nonsense codons
    E. recognizes splice donor sites
    


17. Coenzymes that are required by the pyruvate dehydrogenase multienzyme complex are
    A. biotin, CoA, NAD⁺, pyridoxal phosphate, and lipoic acid
    B. thiamine pyrophosphate, tetrahydrofolate, lipoic acid, FAD, and CoA
    C. thiamine pyrophosphate, lipoic acid, FAD, CoA, and NAD⁺
    D. FAD, CoA, NAD⁺, pyridoxal phosphate, and tetrahydrofolate
    E. lipoic acid, FAD, CoA, NAD⁺, and cobalamin
    


18. Ketosis is characterized by the abnormal accumulation of ____________ in the blood and urine.
    A. ketosugars, such as fructose, xyulose, and ribulose
    B. a-ketoacids, such as pyruvate and a-ketoglutarate
    C. long chain b-ketoacyl-CoA thioesters
    D. succinate,oxaloacetate, and isocitrate
    E. acetoacetate, b-hydroxybutyrate, and acetone