Enzyme activity projects with pineapple or potato let you measure how living cells speed up chemical reactions. Fresh pineapple contains bromelain, a protease that breaks down proteins, while potato contains catalase, an enzyme that breaks down hydrogen peroxide. These experiments matter because enzymes control digestion, metabolism, food processing, and many medical tests.
By changing one condition at a time, you can see how temperature, pH, and substrate concentration affect reaction rate.
Key Facts
- Catalase reaction: 2H2O2 -> 2H2O + O2
- Bromelain breaks peptide bonds in proteins such as gelatin or collagen.
- Reaction rate = change in product or reactant amount / time.
- Higher substrate concentration usually increases enzyme activity until active sites are saturated.
- Each enzyme has an optimum temperature and optimum pH where activity is highest.
- Denaturation changes an enzyme's shape and can greatly reduce activity.
Vocabulary
- Enzyme
- A biological catalyst, usually a protein, that speeds up a chemical reaction without being used up.
- Substrate
- The specific reactant molecule that binds to an enzyme's active site.
- Active site
- The region of an enzyme where the substrate binds and the reaction takes place.
- Bromelain
- A protease enzyme found in pineapple that breaks proteins into smaller peptides.
- Catalase
- An enzyme found in many cells, including potato cells, that breaks hydrogen peroxide into water and oxygen gas.
Common Mistakes to Avoid
- Changing more than one variable at once makes the result hard to interpret because you cannot tell which factor caused the change in activity.
- Using canned pineapple instead of fresh pineapple can give weak bromelain results because heat processing may denature the enzyme.
- Comparing foam height at different times is misleading because reaction rate should be measured over the same time interval for every trial.
- Forgetting a control sample makes conclusions weaker because you need a baseline without active enzyme or without substrate for comparison.
Practice Questions
- 1 A potato catalase trial produces 18 mL of oxygen gas in 60 seconds. What is the reaction rate in mL/s?
- 2 In a bromelain test, gelatin firmness decreases from 9 units to 3 units in 12 minutes. What is the average change in firmness per minute?
- 3 A student tests catalase at 10°C, 25°C, 37°C, and 80°C. The 37°C sample produces the most foam, while the 80°C sample produces almost none. Explain what this pattern suggests about enzyme activity and enzyme shape.