Here are several practice problems…

 

  1. Identify the hybridization and bond angles for each carbon, oxygen, and nitrogen atom in the following molecules
    1. Tyrosine at physiological pH.
    2. Acetylcholine
    3. Norepinephrine
  2. An enzyme catalyzes reaction rates by lowering a reaction’s activation energy.  Calculate by what factor the reaction rate increases for an enzyme-catalyzed reaction with an activation energy of 20 kJ/mol compared with the rate when no catalyst is present and the activation energy is 100 kJ/mol.
  3. Phosphoric acid has pKa’s of 1.97, 6.82, and 12.5.
    1. Draw the complete Lewis structures for the two most concentrated forms at a physiological pH of 7.4.
    2. Calculate the exact relative amounts of these two forms at a pH of 7.4.
    3. Draw the mechanism for the reactions that occur among phosphate, ethanolamine, and glycerol to form a part of a phospholipid structure often found in cell membranes.
  4. A recent study demonstrated that the replacement of a carboxylic acid group with a phosphonic acid provided increased acidity while also lowering the log P value. The presence of phosphonic acid functionalities in several marketed drugs demonstrates the utility of this approach.  One of the phosphonic acid substituted compounds being examined exhibited a log P value of 1.22.  Calculate the volume of 1-octanol required to extract 99% of the moles of this substance out of 1.0 liters of water.
  5. Eukaryotic cell membranes have chloride concentrations of 110 mM and 5 mM across cell membranes.
    1. Calculate the Nernst potential, draw a diagram, and clearly explain what the Nernst potential physically represents.
    2. Draw the complete molecular structure of the GABA neurotransmitter at physiological pH and explain what happens when a GABA receptor is activated.  Identify several substances that activate GABA receptors.
  6. Diagram how potential energy changes as the aspartic acid side group approaches the nitrogen end of acetylcholine.  Draw the structures and show the nature of this interaction.
  7. Drugs A, B, and C have ED50’s of 3 nM, 6 mM, and 0.001 mM respectively.  Substance A has twice the efficacy of B and one-third the efficacy of C.  Draw a dose response diagram that clearly shows the relative potencies and efficacies of these substances on a given target.