Question 1: Define the Lock and Key Theory as it relates to enzyme activity.

Answer: The Lock and Key Theory describes how enzymes have specific active sites that exactly fit their substrate molecules, like a key fitting a lock, enabling the enzyme to catalyse a chemical reaction.

Question 2: Explain why enzymes are specific to their substrates according to the Lock and Key Model.

Answer: Enzymes are specific because their active sites have a unique shape that only fits specific substrate molecules, similar to how a specific key fits a particular lock.

Question 3: Describe what happens at the molecular level when an enzyme and substrate interact in the Lock and Key Model.

Answer: The substrate binds to the enzyme's active site, which has a complementary shape. This binding forms an enzyme-substrate complex, lowering the activation energy needed for the reaction. The substrate is then converted into products, which are released, leaving the enzyme unchanged and ready to catalyse another reaction.

Question 4: Identify the variables that could affect enzyme activity in an experiment testing enzyme function.

Answer: Variables include temperature, pH, enzyme concentration, substrate concentration, and the presence of inhibitors.

Question 5: Calculate the rate of enzyme activity if 50 units of substrate are processed in 10 minutes. Show your working.

Answer: Rate = Total units of substrate processed / Time (minutes) = 50 units / 10 min = 5 units per minute.

Question 6: A student tests enzyme activity at different pH levels. At pH 5, the enzyme shows 80% activity; at pH 7, it shows 100%; and at pH 9, it drops to 60%. Explain what this data suggests about the enzyme’s pH preference.

Answer: The enzyme has optimal activity around pH 7, with decreased activity at more acidic or alkaline pH levels, indicating it functions best in neutral conditions.

Question 7: Describe a practical experiment to test the effect of temperature on enzyme activity, including the variables involved and safety precautions.

Answer: To test temperature effects, set up multiple test tubes with the same enzyme and substrate solutions. Place the tubes in water baths set at different temperatures (e.g., 0°C, 25°C, 37°C, 50°C). Measure enzyme activity by assessing product formation or substrate breakdown over time. Variables include temperature (independent), enzyme and substrate concentrations (controlled). Safety precautions include handling hot water baths carefully and wearing safety glasses.

Question 8: A scenario: An enzyme’s activity decreases significantly when the temperature exceeds 50°C. Explain the molecular basis for this observation.

Answer: High temperatures can denature the enzyme, causing the active site to change shape and lose its specificity, thus reducing or stopping enzyme activity.

Question 9: In industrial applications, why is understanding enzyme specificity important for designing enzyme-based processes?

Answer: Understanding enzyme specificity allows for selecting the correct enzyme for a particular reaction, increasing efficiency and reducing unwanted side reactions.

Question 10: Explain how the Lock and Key Theory differs from the Induced Fit Model in enzyme activity.

Answer: The Lock and Key Theory suggests the active site has a fixed shape that matches the substrate exactly, while the Induced Fit Model proposes that the active site changes shape upon substrate binding to fit the substrate more snugly.