Energy is a one of the “Big Ideas” of AP Biology and is also included in the Next Generation Science standards. Students don’t usually learn about the laws of thermodynamics until they take chemistry of physics. Most biology books do have a chapter on cellular metabolism, usually near chapters on cellular respiration. Beginning biology students can become overwhelmed if too much emphasis is placed on the chemistry aspects of the equations, but I’ve found that even my freshman can grasp the basic concepts of enzymes, substrates and activation energy of a reaction. A popular enzyme activity in my Intro Bio class involves putting hydrogen peroxide on liver and observing the bubbles, which are the products.
AP Biology classes must go into more detail about reaction rates and how enzymes work at optimal temperatures and pH. For those classes, I use lactase as a focus enzyme as students explore the properties of enzymes. HHMI has excellent resources on human evolution and lactase persistence which I also include in the unit.
This worksheet can be used as a supplement to other enzyme activities, where students examine graphics showing properties of enzymes. First, they label the enzyme, substrate, active site, and products. Then they view a graph showing energy changes with and without an enzyme, revealing how enzymes lower activation energy. Students also examine a graph showing the optimal pH of pepsin and lipase. Finally, a graphic illustrates how competitive inhibition and allosteric inhibition can reduce the speed of enzymatic reactions.