Solved Enzymes Number: Name Period Date Enzyme Worksheet 1 ... - Free Printable

11) Label the following terms in the picture

Based on the diagram provided:

- a → Substrate
*(The molecule that binds to the enzyme and is converted into products.)*

- b → Active site
*(The region on the enzyme where the substrate binds and the reaction occurs.)*

- c → Enzyme
*(The protein catalyst that speeds up the reaction by lowering activation energy.)*

- d → Product(s)
*(The molecules formed after the substrate is transformed during the reaction.)*

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12) Using Graph 1, explain how enzymes work. Include the term activation energy and compare the two curves, explaining which is with the enzyme.

Graph 1 shows the change in free energy during a chemical reaction, with two curves: one for the reaction without an enzyme and one with an enzyme.

- The activation energy (Eₐ) is the minimum energy required for a reaction to proceed. It is represented by the energy "hill" between reactants and products.
- The curve labeled "Eₐ without enzyme" has a higher peak, meaning more energy is needed to start the reaction.
- The other curve (lower peak) represents the reaction with the enzyme. This curve has a lower activation energy because the enzyme stabilizes the transition state, making it easier for the reaction to occur.
- Enzymes do not alter the overall energy change (ΔG) of the reaction — they only speed up the rate by lowering the activation energy.
- Therefore, the curve with the lower peak is the one with the enzyme.

> ✔ Conclusion: Enzymes increase the rate of reaction by lowering the activation energy barrier, allowing the reaction to proceed faster at a given temperature.

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13) Using Graph 2, explain how temperature affects enzyme activity. Use the word denature.

Graph 2 shows enzyme activity as a function of temperature.

- At low temperatures (e.g., 0–20°C), enzyme activity is low because molecules move slowly and collisions between enzyme and substrate are infrequent.
- As temperature increases (20–40°C), enzyme activity rises sharply because molecular motion increases, leading to more frequent and effective collisions.
- At the optimum temperature (~40°C), enzyme activity is highest — this is the ideal temperature for maximum catalytic efficiency.
- Beyond this point (e.g., above 50°C), enzyme activity drops rapidly due to denaturation.
- Denaturation means the enzyme’s shape changes irreversibly, especially the active site, due to breaking of hydrogen bonds and other weak interactions.
- Once denatured, the enzyme can no longer bind the substrate effectively, so activity plummets.

> ✔ Conclusion: Temperature increases enzyme activity up to an optimum point, but excessive heat causes denaturation, destroying enzyme function.

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14) Using Graph 3, explain how pH affects enzyme activity. Relate to temperature effects.

Graph 3 shows enzyme activity as a function of pH.

- Each enzyme has an optimum pH at which its activity is highest. In this graph, the optimum pH is around 7, suggesting this might be a neutral pH enzyme (like many in the human body).
- At pH values below or above the optimum, enzyme activity decreases.
- This happens because changes in pH affect the ionization of amino acid side chains in the enzyme, altering its shape and charge distribution.
- If pH deviates too much, the enzyme may become denatured, just like with high temperature.
- Like temperature, extreme pH disrupts hydrogen bonding and electrostatic interactions that maintain the enzyme’s three-dimensional structure.
- Both temperature and pH affect enzyme activity by influencing the enzyme's conformation. When either factor is outside the optimal range, the enzyme becomes less effective or completely inactive due to structural changes.

> ✔ Conclusion: pH affects enzyme activity by altering the enzyme's shape and charge, similar to how temperature affects it. Both factors can lead to denaturation if conditions are too extreme, resulting in loss of function.

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