Enzyme Activity in a Washing Powder Trial
A student tests a biological washing powder containing a protease. She sets up four trials, each with 10 mL of a 2% milk solution (protein) and a small square of photographic film coated in gelatin. Each tube is held at a different temperature for 10 minutes, then the time for the gelatin to clear is recorded: 10 degrees C took 18 minutes, 40 degrees C took 3 minutes, 60 degrees C took 4 minutes, and 80 degrees C did not clear within 30 minutes. She concludes that the enzyme works best at 60 degrees C because that trial was almost as fast as 40 degrees C.
1. Evaluate her conclusion using the data and your knowledge of enzyme structure.
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The data show the shortest clearing time at 40 degrees C (3 min), so the optimum among the tested temperatures is closest to 40 degrees C, not 60 degrees C. At 80 degrees C the gelatin never cleared, consistent with denaturation: the enzyme's active site changes shape and substrate no longer binds. The 60 degrees C result (4 min) is slightly slower than 40 degrees C, so her claim that 60 is best is not supported. She confused 'almost as fast' with 'fastest'.
2. Suggest one improvement to the method and explain how it would make the conclusion more reliable.
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Test more temperatures between 30 and 70 degrees C (e.g. every 5 degrees) so the optimum can be located rather than guessed between widely spaced points. Alternatively, repeat each temperature at least three times and average, reducing the effect of random error such as uneven film thickness or timing judgement. Either change gives a finer, more reproducible picture of where activity peaks, so the optimum temperature can be stated with confidence.