Passage I

Enzymes catalyze (speed up) chemical reactions. The pancreas (a digestive organ) secretes 4 types of digestive enzymes—amylase, nuclease, lipase, and protease. Each type of enzyme catalyzes the breakdown of a different type of molecule in the digestive tract (see Table 1).

An enzyme's activity can be affected by pH. Figure 1 shows, for each type of enzyme listed in Table 1, how relative activity (percent of the greatest measured activity) varies with pH.