Fresh pineapple contains bromelain, an enzyme that breaks apart protein. When you add it to Jello, bromelain digests the gelatin that gives Jello its firm texture — and the mixture stays liquid instead of setting. Canned pineapple does not have this effect. The heat from canning destroys the enzyme, so that batch sets normally.

The conditions around an enzyme change how well it works. In this experiment, albumin — a common protein — is placed into test tubes at seven different pH levels. Every ten minutes, a chemical dye is added to one tube from each group, and after spinning the samples in a centrifuge, color change reveals how much digestion has occurred. A spectrophotometer measures absorbance at 580 nm for a more precise reading. As pH rises, digestion speeds up sharply; at pH eight and above, the protein breaks down almost right away, while lower pH levels slow the process down.

Amylase, found in saliva and pancreatic juice, speeds up the breakdown of starch into sugar. When it is boiled, it no longer works. You set up five test tubes with different combinations of starch solution and amylase — some with active enzyme, others with boiled enzyme that has been deactivated. After placing all five in a warm water bath, you test each tube with iodine and Benedict's solution. Iodine turns blue-black when starch is present; Benedict's solution turns orange when sugar is present. The results show clearly which tubes still contain starch and which have been broken down.

Catalase, found in living tissues like liver and potato, triggers a rapid fizzing reaction when it meets hydrogen peroxide, producing oxygen gas. To measure how fast this happens, you place a small amount of liver or potato extract in a test tube, pour in diluted hydrogen peroxide, and immediately start timing. The reaction creates a rising column of froth, and the reaction rate equals froth height divided by time. Keeping the extract on ice before use helps preserve the enzyme. When you test variables like temperature, you can see directly how changing conditions alter the speed of this enzyme-driven process.

Heat can stop enzymes from working — and catalase in potatoes shows this clearly. Catalase breaks hydrogen peroxide into oxygen and water, and the oxygen it releases can push a small piece of filter paper to the surface of a test tube. Below 40 degrees Celsius, the paper rises in seconds. Above 45 degrees, the enzyme starts to break down and the reaction slows sharply, marking the temperature where heat begins to destroy it.