(1) AP Biology Lab 2: Enzyme Catalysis

Introduction to Enzymes and Catalase

  • Enzyme lab on enzyme catalysis, focusing on catalase.

  • Catalase: Found in almost all living things; breaks down hydrogen peroxide (H2O2) into water (H2O) and oxygen.

    • Present in yeast, used in the experiment.

What is an Enzyme?

  • Defined as biological molecules that act as catalysts.

  • Catalysts speed up reactions and are not consumed in the process.

  • Example of Lactase: Breaks down lactose (milk sugar); fits like a key in a lock, enabling reaction without changing the enzyme’s shape.

Experiment Setup

  • Use filter paper dipped in varying yeast concentrations (0 to higher amounts).

  • Place filter paper in hydrogen peroxide solution.

  • Observation:

    • No yeast present: Filter paper sinks and stays at the bottom.

    • Yeast present: Filter paper floats as catalase breaks down hydrogen peroxide, releasing oxygen bubbles.

  • Measure time taken for paper to float to determine reaction rate (floats per second).

Results and Expectations

  • Rate of reaction increases with more yeast, forming a curve.

  • At zero yeast concentration, rate is zero; never floats.

  • Reaction rate does not continue to rise linearly due to depletion of hydrogen peroxide as reaction progresses.

Rate Measurement

  • Rate determined by number of floats per second.

  • Could also measure decrease in hydrogen peroxide or increase in oxygen produced.

  • Key focus in this lab: Increase in enzyme concentration affects reaction rate.

Factors Affecting Enzyme Activity

Substrate Concentration

  • Increasing substrate increases reaction rate initially, due to more availability for breakdown.

Temperature Effects

  • Reaction rate increases until an optimal temperature, then decreases:

    • Higher temperatures increase molecular motion, enhancing enzyme activity.

    • Excessive heat denatures enzymes, preventing substrate binding.

    • Optimal temperature for human enzymes is around 37°C.

    • Extremophiles (e.g., bacteria in hot environments) have higher optimal temperatures.

pH Effects

  • Similar trend as temperature; has an optimal pH where the enzyme is most active.

  • Deviations (too acidic or too basic) can lead to enzyme denaturation.