Cop 2015 Pharmaceutics I Practice With Aa Charges

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Cop 2015 Pharmaceutics I Practice With Aa Charges - Quiz


pH, functional groups, etc


Questions and Answers
  • 1. 

    Aspartic acid is an amino acid with three different pKas. The approximate pKas are as follows: pKaC = 2.0 pKaN = 9.9 pKaR = 3.9 At a pH of 12, what is the charge of the most abundant species present?

    • A.

      0

    • B.

      2+

    • C.

      2-

    • D.

      1-

    Correct Answer
    C. 2-
    Explanation
    At a pH of 12, the solution is highly basic. The pKa values indicate the pH at which half of the aspartic acid molecules will be deprotonated. Since the pH is much higher than the pKa values, all three ionizable groups (carboxyl group, amino group, and side chain) will be deprotonated. This means that the most abundant species present will have a negative charge, specifically a charge of 2-.

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  • 2. 

    Aspartic acid is an amino acid with three different pKas. The approximate pKas are as follows: pKaC = 2.0 pKaN = 9.9 pKaR = 3.9 At a pH of 7, what is the charge of the most abundant species present?

    • A.

      0

    • B.

      2+

    • C.

      2-

    • D.

      1-

    Correct Answer
    D. 1-
    Explanation
    At a pH of 7, the charge of the most abundant species present can be determined by comparing the pH to the pKa values. The pKa values represent the pH at which half of the molecules are protonated and half are deprotonated.

    Given that the pH is 7, which is higher than the pKaC of 2.0 and pKaR of 3.9, it can be inferred that the carboxyl group (C) and the side chain (R) are deprotonated. Therefore, they carry a negative charge.

    However, the pH of 7 is lower than the pKaN of 9.9, which suggests that the amino group (N) is protonated and carries a positive charge.

    Since the carboxyl group and the side chain are deprotonated (negative charge) and the amino group is protonated (positive charge), the overall charge of the most abundant species present at a pH of 7 is 1-.

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  • 3. 

    Aspartic acid is an amino acid with three different pKas. The approximate pKas are as follows: pKaC = 2.0 pKaN = 9.9 pKaR = 3.9 What is the pI, isoelectric point, of aspartic acid?

    • A.

      2.0

    • B.

      2.95

    • C.

      7.4

    • D.

      3.9

    Correct Answer
    B. 2.95
    Explanation
    The pI, or isoelectric point, of an amino acid is the pH at which the molecule has no net electrical charge. It can be calculated by averaging the two pKa values that are closest to each other. In this case, the pKa values closest to each other are pKaC (2.0) and pKaR (3.9). Therefore, the pI of aspartic acid would be the average of these two values, which is 2.95.

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  • 4. 

    If the pKa of HA in this equation is 4.2, the major species present at pH 6 will be ionized.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    At pH 6, which is higher than the pKa of HA (4.2), the solution will be more basic. This means that the concentration of H+ ions will be lower, promoting ionization of HA. Therefore, the major species present at pH 6 will be the ionized form of HA.

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  • 5. 

    If the pKa of HA in this equation is 6.9, the major species present at pH 3.9 will be ionized.

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    The pKa value indicates the acidity of a compound. In this case, if the pKa of HA is 6.9, it means that at a pH lower than 6.9, the compound will be mostly in its protonated form (non-ionized). Since the pH of 3.9 is lower than 6.9, the major species present at pH 3.9 will be non-ionized. Therefore, the correct answer is False.

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  • 6. 

    Asprin is an acidic drug. One way to counteract aspirin overdose is to:

    • A.

      Increase pH of the urine

    • B.

      Decrease pH of the urine

    • C.

      Initiate forced acid diuresis

    Correct Answer
    A. Increase pH of the urine
    Explanation
    Increasing the pH of the urine is a way to counteract aspirin overdose because aspirin is an acidic drug. By increasing the pH of the urine, the acidic nature of aspirin can be neutralized, making it less toxic and easier to eliminate from the body. This can be achieved by administering alkaline substances or medications that can raise the pH of the urine, such as sodium bicarbonate or acetazolamide.

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  • 7. 

    In the equation above, the anion comes from the base.

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    The explanation for the answer "False" is that in the equation, the anion does not come from the base. An anion is a negatively charged ion, while a base is a substance that accepts protons or donates pairs of electrons. In the equation, the anion would typically come from the acid, not the base. Therefore, the statement is incorrect.

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  • 8. 

    In order to make a drug more water soluble, you would increase the overall charge.

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Increasing the overall charge of a drug can make it more water soluble because water is a polar molecule, meaning it has a positive and negative end. By increasing the overall charge of the drug, it can interact more easily with the polar water molecules, allowing it to dissolve more readily in water. This can be achieved by adding functional groups to the drug molecule that have a charge, such as amino or carboxyl groups.

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  • 9. 

    Melphalan, depicted above, is a drug used in chemotherapy. At physiological pH, the drug has two charged groups as shown in the above figure. This drug will diffuse passively across cellular membranes.

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    Melphalan, depicted above, is a drug used in chemotherapy. At physiological pH, the drug has two charged groups as shown in the above figure. Charged groups are unable to passively diffuse across cellular membranes. Therefore, the statement that this drug will diffuse passively across cellular membranes is false.

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