Culmination Practice Quiz

54 Questions | Total Attempts: 145

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Culmination Practice Quiz

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Questions and Answers
  • 1. 
    A 27-year-old intravenous drug user who shared needles with others for several years experiences flu-like symptoms with fever, malaise and muscle aches. The patient also suffers from anorexia, diarrhea and severe weight loss. Physical examination revealed generalized lymph node enlargement and laboratory tests were positive for the human immunodeficiency virus (HIV). Your diagnosis indicates that this patient suffers from acute immunodeficiency syndrome (AIDS) and you prescribe therapy with the nucleoside analog dideoxycytidine (ddC). All of the following statements regarding ddC are true, EXCEPT:
    • A. 

      Dideoxycytidine tri-phosphate cannot be incorporated into growing DNA chains.

    • B. 

      Dideoxycytidine is an analog of the nucleoside deoxycytidine.

    • C. 

      Dideoxycytidine tri-phosphate is used to terminate DNA chain elongation during DNA sequencing.

    • D. 

      Dideoxycytidine has hydrogen groups on the 2’- and 3’-carbons of deoxyribose.

    • E. 

      Dideoxycytidine is converted to a nucleoside tri-phosphate by cellular kinases.

  • 2. 
    A strain of E. coli is unable to induce the operons encoding the genes responsible for the metabolism of several sugars that can normally act as carbon sources when glucose is unavailable. The most likely explanation is a mutation that...
    • A. 

      Alters the specificity of the sigma factor of RNA polymerase.

    • B. 

      Prevents the binding of RNA polymerase to promoters.

    • C. 

      Increases the affinity of CAP for cAMP.

    • D. 

      Decreases the affinity of CAP for cAMP.

    • E. 

      Causes CAP to bind constitutively to CAP-binding sites.

  • 3. 
    What two organelles are shown in the micrograph?
    • A. 

      Peroxisomes, Rough Endoplasmic Reticulum

    • B. 

      Lipid Droplets, Smooth Endoplasmic Reticulum

    • C. 

      Mitochondrion, Smooth Endoplasmic Reticulum

    • D. 

      Lysosomes, Golgi Apparatus

  • 4. 
    Biochemical mechanisms for regulating enzyme activity include ALL of the following EXCEPT which ONE:
    • A. 

      Allosteric interactions

    • B. 

      Phosphorylation of amino acid side chains

    • C. 

      Proteolytic cleavage of peptide bonds within the zymogen

    • D. 

      Degradation of the enzyme

    • E. 

      Converting activated enzymes to zymogens

  • 5. 
    Match each of the statements with one or more of the structures shown below. Which statement CANNOT be matched with a structure?
    • A. 

      This amino acid residue can form disulfide bonds under oxidizing conditions.

    • B. 

      This residue can adopt a cis conformation of the peptide bond within a protein.

    • C. 

      The side chain of this amino acid has multiple atoms that can participate in hydrogen bonds.

    • D. 

      The side chain of this amino acid is positively charged at physiologic pH.

    • E. 

      This amino acid can serve as an attachment site for O-linked polysaccharides (sugars) in glycoproteins.

  • 6. 
    Which ONE of the following best explains the side effects of ALLI (ORLISTAT), including fatty stools, diarrhea, and flatulence?
    • A. 

      Failure to inhibit gastric lipase

    • B. 

      Excess undigested fats

    • C. 

      Accumulation of Orlistat in the intestinal tract

    • D. 

      Liver damage

    • E. 

      Non-specific inhibition of many enzymes

  • 7. 
    One of our cases of the week is a 32 year old male college graduate who works full time. He is 68” inches tall and weighs 154 pounds. His blood pressure is 135/82 and his glycated hemoglobin (a1C) is 6.2%. Which of the following statements is false?
    • A. 

      His blood pressure of 135/82 identifies him as risk for hypertension

    • B. 

      His BMI places him in the “normal” range

    • C. 

      We should repeat the a1C and order a fasting plasma glucose (FPG) test on a non-urgent basis

    • D. 

      His blood pressure is within the “normal” range

    • E. 

      His hemoglobin a1C level of 6.2% identifies him as at increased risk of diabetes

  • 8. 
    Hemoglobin is an allosteric protein. This means that an interaction at one site has an effect at a spatially distinct site in the protein. Which ONE of the following statements about allosteric effects of hemoglobin is CORRECT?
    • A. 

      Nitric oxide (NO) is released from Hb preferentially at sites of active metabolism, because a cysteine has a much higher affinity for NO in oxyhemoglobin than in deoxyHb.

    • B. 

      Hemoglobin and myoglobin molecules can bind 2,3-bisphosphoglycerate, which decreases their affinity for oxygen.

    • C. 

      Carbon dioxide increases the affinity of hemoglobin for oxygen both by binding to the N-terminus and through the Bohr effect.

    • D. 

      The Hill Coefficient of hemoglobin indicates that hemoglobin tetramers have no more than three oxygen molecules bound.

    • E. 

      Sites of active metabolism have higher concentration of carbonic acid, which shifts the hemoglobin oxygen dissociation curve to the left.

  • 9. 
    A 40 year old woman and her two children went to the doctor with complaints of headaches, nausea, weakness and dizziness. At first, the physician thinks that the family is suffering from the flu. However, after hearing about the new wood-burning stove installed in their house this past winter, the physician suspected carbon monoxide poisoning. To treat them for carbon monoxide poisoning, the physician…
    • A. 

      Gave them hydroxyurea to increase the synthesis of HbF.

    • B. 

      Had them ingest a reducing agent to regenerate the oxygen binding form of Hb.

    • C. 

      Gave them hydroxyurea to increase the synthesis of HbF.

    • D. 

      Administered air with a higher percent of carbon dioxide than is normal, to compete with the carbon monoxide.

    • E. 

      Administered 100% oxygen to displace the competitive inhibitor.

  • 10. 
    “Stripped” hemoglobin is Hb obtained from RBCs that have been lysed (broken open) and dialyzed to remove any small molecules such as organic phosphates. The oxygen saturation curves for Hb from whole blood and for stripped Hb are shown below. Which ONE of the following statements related to these curves is CORRECT?
    • A. 

      In going from a pO2 of 20mmHg to a pO2 of 100mmHg, stripped Hb takes up about three times as much oxygen as does Hb from whole blood, per mole of tetramer.

    • B. 

      In going from a pO2 of 100mmHg to a pO2 of 20mmHg, Hb from whole blood releases about three times as much oxygen as does stripped Hb, per mole of tetramer.

    • C. 

      The P50 value for stripped Hb is ~ 40mmHg lower than that for whole blood.

    • D. 

      The P50 value for stripped Hb is ~ 15mmHg higher than that for whole blood.

    • E. 

      Changing the pH would not affect the oxygen saturation curve of the stripped Hb.

  • 11. 
    Which ONE of the following statements concerning nitric oxide is CORRECT? The delivery of nitric oxide by hemoglobin....
    • A. 

      Depends on the differing reactivity of the R and T forms of Hb

    • B. 

      Leads to decreased blood flow at tissue sites with low oxygen pressure.

    • C. 

      Can competitively inhibit cyanide poisoning.

    • D. 

      Competes with carbon dioxide binding.

    • E. 

      Is mediated by formation of C?-CH2-S-NO bond with Met.

  • 12. 
    You are studying a biochemical pathway that requires ATP as an energy source. To your dismay, the reactions soon stop, partly because the ATP is rapidly used up and partly because an excess of ADP builds up and inhibits the enzymes involved. You are about to give up when the following table from a biochemistry textbook catches your eye.
    • A. 

      Pyrophosphate

    • B. 

      Glucose 6-phosphate and enzyme E

    • C. 

      Creatine phosphate and enzyme A

    • D. 

      A vast excess of ATP

    • E. 

      Pyrophosphate and enzyme D

  • 13. 
    A common means of providing energy to an energetically unfavorable reaction in a cell is by…
    • A. 

      Coupling of the synthesis of ATP to the reaction.

    • B. 

      Enzyme catalysis of the reaction.

    • C. 

      Generation of a higher temperature by the cell.

    • D. 

      Coupling of ATP hydrolysis to the reaction.

    • E. 

      Transfer of a phosphate group from the substrate to ADP.

  • 14. 
    Which of the following reactions are energetically favorable?
    • A. 

      Base + sugar + phosphate --> nucleotide

    • B. 

      N2 + H2 --> ammonia

    • C. 

      Sucrose --> CO2 + H2O

    • D. 

      CO2 + H2O --> sugar

    • E. 

      Amino acid + amino acid --> peptide

  • 15. 
    A comatose laboratory technician is rushed into the emergency room. A symptom you observe is that her body is unusually warm to the touch, indicating an extremely high fever. She dies while you are examining her. You later learn that her lab has been working on metabolic inhibitors and that there is a high likelihood that she ingested, by accident, an extremely high dose of one of them. The most likely compound is….
    • A. 

      2,4-dinitrophenol

    • B. 

      Atractyloside

    • C. 

      Rotenone

    • D. 

      Oligomycin.

    • E. 

      Cyanide

  • 16. 
    When Peter Mitchell first proposed the chemiosmotic mechanism for oxidative phosphorylation, it was not taken seriously. Slowly, evidence accumulated to support it. Key pieces of evidence that support the chemiosmotic mechanism include all of the following EXCEPT:
    • A. 

      Disruption of the inner mitochondrial membrane stops ATP formation.

    • B. 

      Complex I can only react with NADH from the matrix side while complex III can only reduce cytochrome c from the intermembrane space.

    • C. 

      A pH gradient is set up across the inner mitochondrial membrane, with the pH higher in the matrix.

    • D. 

      At least one component of each major electron transport complex is coded for by mt DNA.

    • E. 

      Oxidation-reduction reactions of the electron transport chain generate a gradient of protons across the inner mitochondrial membrane.

  • 17. 
    A defect in the adenine nucleotide carrier (also known as adenine nucleotide translocase) would lead to which of the following?
    • A. 

      A decrease in the cytosolic concentration of ADP.

    • B. 

      A decrease in the activity of mitochondrial outer membrane transport proteins.

    • C. 

      An increase in mitochondrial AMP.

    • D. 

      An increase in mitochondrial ATP production.

    • E. 

      A decrease in the cytosolic concentration of ATP.

  • 18. 
    Complete the following sentence so that it is CORRECT: “Complete oxidation of one acetyl CoA leads to...”
    • A. 

      The reduction of one NAD+.

    • B. 

      The net consumption of one oxaloacetate.

    • C. 

      The net synthesis of one citrate.

    • D. 

      The production of six ATPs.

    • E. 

      The release of two CO2.

  • 19. 
    In addition to the proteins of the pyruvate dehydrogenase complex, the conversion of pyruvate to acetyl CoA also requires which ONE of the following combinations of co-factors:
    • A. 

      CoA, lipoic acid, biotin and ATP

    • B. 

      CoA, ATP, NAD+ and riboflavin

    • C. 

      CoA, thiamine pyrophosphate and folic acid

    • D. 

      CoA, lipoic acid, thiamine pyrophosphate and FAD

  • 20. 
    Many factors contribute to studying causation; the definition of “a cause” is….
    • A. 

      An event or exposure that occurs more often in people with a disease than without

    • B. 

      An event, condition, or characteristic that plays an important role in disease occurrence..

    • C. 

      An event that precedes the onset of a disease

    • D. 

      A hazard or exposure that occurs in workplaces where people get sick.

    • E. 

      All of the above

  • 21. 
    DNA gyrase is a prokaryotic DNA topoisomerase II. Which ONE of the following DNA conformations shown on the left will be converted to the conformation shown on the right upon treatment with DNA gyrase?A) B) C) D)
    • A. 

      A

    • B. 

      B

    • C. 

      C

    • D. 

      D

  • 22. 
    A middle-aged man shows symptoms characteristic of tuberculosis, a disease condition caused by the bacterium Mycobacterium tuberculosis. Laboratory analysis of a sputum specimen revealed that in addition to the wild-type Mycobacterium tuberculosis bacterium, a variant strain was also present that showed a conditional mutation affecting the 5’ to 3’ exonuclease activity of DNA polymerase I. Which ONE of the following phenotypes is the most obvious defect associated with a conditional mutation affecting the 5’ to 3’ exonuclease activity of DNA polymerase I under conditions where it is INACTIVE?
    • A. 

      The bacterial genome shows a defect in lagging strand DNA chain elongation.

    • B. 

      The bacterial genome shows a defect in mismatch repair.

    • C. 

      The bacterial genome shows accumulation of telomeric repeats.

    • D. 

      The bacterial genome shows a defect in the removal of RNA primers.

    • E. 

      The bacterial genome shows an increased number of replication errors.

  • 23. 
    All of the following statements are true about transposition, EXCEPT:
    • A. 

      Transposons may either activate or inactivate a gene.

    • B. 

      In transposition, both the donor and target sites must be homologous.

    • C. 

      Integration of human immunodeficiency virus (HIV) in the human genome occurs via a “transposition-like” mechanism.

    • D. 

      Transposons have “insertion sequences” that are recognized by transposase.

    • E. 

      Transposons can move from one location to a different one within a chromosome.

  • 24. 
    Dynein, kinesin and myosin are molecular motors. Select the incorrect statement:
    • A. 

      Kinesins and dynein can move on the same structure.

    • B. 

      The “power stroke” occurs when the products of hydrolysis are released.

    • C. 

      All three classes of motors are ATPases.

    • D. 

      Dynein moves on microtubules towards the centrosome.

  • 25. 
    The role of ATP hydrolysis in actin polymerization is similar to the role of GTP hydrolysis in tubulin polymerization (N=nucleotide). Which statement is incorrect?
    • A. 

      When the subunit at the + end of the polymer is NTP, the end is more stable than if the nucleotide is NDP.

    • B. 

      The energy of NTP hydrolysis is required for polymerization.

    • C. 

      The nucleotide in the subunit at the end of the polymer affects the equilibrium constant of subunit addition at the end.

    • D. 

      NTP hydrolysis occurs after polymerization.

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