Week Four Quiz

  1. A weak base with a pKa of 9.4 distributes between two aqueous compartments, A and B, which are separated by a lipid membrane. The pH of compartment A is 7.4 and the pH of compartment B is 5.4. The volumes of the two compartments are such that protonation of the drug does not influence the pH of either compartment. If, at steady-state, the concentration of the charged drug is 100 µM in compartment A, which of the following statements is/are TRUE?

    1. The concentration of uncharged drug in compartment A is 1 µM
    2. The concentration of uncharged drug in compartment B is 1 µM
    3. The concentration of charged drug in compartment B is 1 µM
    4. A and B

    Show Explanation

  2. Which of the following is/are characteristic of a competitive antagonist?

    1. inhibition by the antagonist is surmountable
    2. potency depends on the concentration of competing agonists
    3. inhibition typically displays use-dependence
    4. A and B

    Show Explanation

  3. A 60 kg woman has a bacterial infection. You decide to administer an antibiotic that has a volume of distribution of 0.2 L/kg. The drug has a clearance of 200 ml/min. If you administer the drug by constant intravenous infusion, approximately how long will it take for the plasma concentration of the antibiotic to reach steady-state levels?

    1. 30 min
    2. 1 hr
    3. 3 hr
    4. 24 hr

    Show Explanation

  4. Cohort studies have which of the following advantages over other studies?

    1. Require relatively few subjects
    2. Obtain results relatively quickly
    3. Allow study of more than one effect of an exposure
    4. Are optimal for the study of rare diseases with long latency

    Show Explanation

  5. Which of the following statements concerning intention-to-treat analysis is NOT an accurate description of this methodological approach?

    1. If investigators conduct an intention-to-treat analysis but count only events in participants who remain within the study at its completion, they will de facto, be conducting a per protocol analysis.
    2. Significant loss to follow-up can introduce the same bias as a per protocol analysis.
    3. Intention to treat analysis makes it possible to include patients lost to follow-up in the denominator of event rates without accounting for their outcomes in the numerator.
    4. Intention-to-treat analysis minimizes bias introduced by loss to follow-up when every possible randomized patient’s health status is known.
    5. If there is significant loss to follow-up, statements that investigators conducted an “intention-to- treat analysis” generally provide little reassurance.

    Show Explanation

  6. Complete β-oxidation of a 16-carbon saturated fatty acid generates which of the following?

    1. 8 molecules of acetyl-CoA/span>
    2. 8 molecules of NADH
    3. 8 β-oxidation cycles
    4. 8 molecules of FADH2

    Show Explanation

  7. Which of the following is true about all amino acids?

    1. Degradation generates products that can enter the citric acid cycle.
    2. They cannot be catabolized by humans.
    3. The first step of catabolism is the removal of the α-amino group.
    4. They can be stored.

    Show Explanation

  8. After several days of starvation, ketone bodies accumulate in the blood because of which of the following?

    1. Glycolysis depletes citric acid intermediates.
    2. Fatty acids are depleted
    3. They cannot be used as fuel.
    4. A llack of oxaloacetate prevents acetyl-CoA entry into the citric acid cycle.

    Show Explanation

  9. A 23-year old woman comes to your clinic with an irregular-shaped mole on her back that contains regions that differ in color. A biopsy and histological analysis indicate melanoma. The woman reports a history of tanning and extensive sun-exposure as a teenager. Which of the following types of mutations most likely lead to development of the melanoma?

    1. Nucleotide deletion
    2. Nucleotide insertion
    3. Pyrimidine dimer
    4. Nucleotide deamination

    Show Explanation

  10. Even limited exposure to ultraviolet light can cause formation of pyrimidine dimers. Which process can repair pyrimidine dimers in the genome?

    1. Base excision repair
    2. Nucleotide excision repair
    3. Mismatch repair
    4. Homologous recombination

    Show Explanation