AP Biology Lab 2: Enzyme Catalysis Study Notes

Lengthy walkthrough of AP Biology Lab 2 on enzyme catalysis.
Main focus on the enzyme catalase, which is prevalent in nearly all living organisms.
Enzymes act as catalysts to speed up chemical reactions without being consumed in the reaction.

Catalase is the enzyme being studied in this lab.
Its primary function is to catalyze the breakdown of hydrogen peroxide (H2O2) into water (H2O) and oxygen (O2).
Observational example: When hydrogen peroxide is applied to a wound, it bubbles due to the action of catalase, which is present in living tissues.

Definition: An enzyme is a biological molecule that serves as a catalyst.
Definition of catalyst: A catalyst is any chemical that accelerates a reaction but is not consumed in the reaction.
Example: Lactase is an enzyme that breaks down lactose, a disaccharide found in milk.
- Mechanism: Lactose fits into the lactase enzyme like a key in a lock, leading to the breakdown into two monosaccharides while keeping lactase unchanged.
- Efficiency: Enzymes like lactase can catalyze millions of reactions per second.

The lab involves testing different concentrations of yeast, which contains catalase.
Filters dipped in varying concentrations of yeast including:
- Zero concentration (control group).
- Incrementally increased concentrations of yeast.
Method:
- Filter paper will be immersed in hydrogen peroxide to observe enzymatic activity.
- Observations will indicate whether the filter paper sinks or floats based on the presence of catalase.

Initial observation with no yeast:
- Filter paper remains at the bottom, indicating no reaction (enzyme activity).
With added yeast:
- The filter paper starts to float as hydrogen peroxide is broken down into water and oxygen bubbles.
- Use of a stopwatch to measure the time taken for the filter paper to float, indicating the rate of reaction.
- Rate calculation: Floats per second calculated based on the time taken.
- Example rate: 1 float divided by time taken in seconds; results in an expected curve of reaction rates based on concentration.

Varying concentrations of yeast yield a graph depicting reaction rates.
Explanation for the curve observed:
- Initially increases with yeast concentration but eventually plateaus due to saturation of substrate (H2O2).
- Too much hydrogen peroxide means further increases in enzyme cannot influence the reaction's speed.

The reaction studied:
- ext{2 H2O2}
  ightarrow ext{2 H2O} + ext{O2}.
Measurement focused on the increase in products (O2) or decrease in substrate (H2O2).

Increasing substrate concentration leads to increased breakdown of hydrogen peroxide.
- Reaction speed increases until enzyme saturation occurs.

Different temperatures measured for enzyme activity:
- Activity increases with temperature up to an optimal point, where molecular motion increases the likelihood of substrate-enzyme interactions.
- Beyond optimal temperature, enzymes denature (i.e., change shape), reducing activity.
- Optimal human enzyme temperature is around 37 degrees Celsius.
- Hydrothermal bacteria may have evolved optimal activities at temperatures near boiling.

Enzyme activity in relation to pH demonstrates an optimum pH similar to temperature effects:
- Curves illustrate that reactor rates increase to an optimum pH and drop off when conditions become too acidic or basic.
- Denaturation occurs in extreme pH environments, affecting enzyme functionality.

Key takeaways included the role of catalase, the importance of measuring reaction rates, and the factors influencing enzyme activity.
Understanding these principles is essential for further studies and practical applications in biology.