This experiment was performed in an upper-level undergraduate biochemistry laboratory course. Students learned how to immobilize an enzyme in a sol-gel matrix and how to perform and evaluate enzyme-activity measurements. The enzyme acid phosphatase (APase) from wheat germ was encapsulated in sol-gel beads that were prepared from the precursor molecule tetramethoxysilane. The enzymatic activities of free and immobilized APase were measured with a colorimetric assay that monitors the formation of "p"-nitrophenolate from "p"-nitrophenylphosphate. Students critically assessed the advantages and disadvantages of sol-gel based enzyme immobilization by investigating the catalytic performance, the enzyme retention, and the reuse capability of the APase sol-gel beads. This experiment exposed students to thoughts and techniques that are important for the biotechnological application of enzymes. (Contains 2 notes, 1 figure, and 2 schemes.)