For many years I have resisted using clickers, mainly because at our university there is no standard universal clicker. I wanted to keep student costs as low as possible but also desired the type of live feedback during a lecture that clicker questions can provide. In both my general chem. (200-300 students) and upper division courses (50-75 students), I now pass out 4 or 5 colored notecards on the first day of class and make sure everyone has one of each color.

This is an in class exercise that I use to emphasize the need for metal ion transport and storage in biochemistry.  Applying the Van't Hoff equation to the Ksp value at 25°C for ferric hydroxide, students calculate the iron concentration at which ferric hydroxide would begin to precipitate out in the blood.  It' s an interesting problem that requires very little math beyond that used in gen chem, and the answer is in stark contrast to the amount of iron that we actually store in our bodies.  

There are three ways to modulate the redox potential of a metalloenzyme:  Changing ligands, changing geometry, and changing solvent. When I introduce this topic in Bioinorganic, I try to give my students concrete examples of each.  I love this one because it applies what they learned in Gen Chem about the Nernst Equation to a biological problem.  Granted, I don't use a metalloenzyme as my example, but I do pull the biological chemistry into it at the end, by referrring to the cytochrome oxidase/O₂ couple.