1. Select the predominant form of Amoxicillin (shown above) at pH 5.3. The pKa of the phenolic -OH is 9.6, the NH3+ is 7.4, and the COOH is 2.4.
2. At what pH would amoxicillin most readily cross a chloride channel? A. 1.8 B. 5.7 C. 8.0 D. 10.5 E. 3.6
3. Using the pK values shown in parentheses in the above diagram, select the pI of the tripeptide Arginiyltyrosinylcystyl from the following choices: A. 11.6 B. 5.0 C. 5.6 D. 8.6 E. 9.5
4. Using the same structure above for question 36, what is the net charge at pH 11? A. 0 B. +2 C. +1 D. -2 E. -1
5. A transition-state analog:
A. is more stable when binding to an enzyme than the normal substrate. B. resembles the active site of general acid-base enzymes.
C. resembles the transition-state structure of the normal enzyme-substrate complex.
D. stabilizes the ground state for the normal enzyme-substrate complex.
E. typically reacts more slowly with an enzyme than the normal substrate.
6. Which amino acid is modified in the conversion of prothrombin to thrombin? A. Glycine B. Alanine C. Arginine D. Aspartic acid E. Glutamic acid
7. Which of the following statements about allosteric control of enzymatic activity is true? A. Allosteric activators increase the Km of the substrate. B. Allosteric proteins are generally composed of multiple subunits. C. An effector may only inhibit the activity of an enzyme.
D. Binding of an effector changes the amino acid sequence of the enzyme molecule.
E. An allosteric effector competes with the substrate for binding the active site.
8. In competitive inhibition, an inhibitor: A. binds at several different sites on an enzyme. B. binds covalently to the enzyme. C. binds only to the ES complex. D. binds reversibly at the active site. E. lowers the characteristic Km of the substrate.
9. Which amino acid will most likely be found in a turn? A.