Explain the relationship between yeast concentration and enzyme activity in decolorizing methylene blue, and outline the experimental procedure.

Okay, Delcie, let's work through question 3.

a) Suggest a Hypothesis for your experiment:
If the concentration of yeast suspension (or stale milk) increases, then the activity of reductase enzymes will increase, leading to a faster decolorization of methylene blue.

b) Describe your procedure:

1. Prepare a stock solution of yeast suspension (or stale milk).
2. Prepare the following percentage dilutions of the stock solution using a suitable diluent (e.g., distilled water or fresh milk):
   • 0% dilution (100% stock solution)
   • 20% dilution (20% stock solution, 80% diluent)
   • 40% dilution (40% stock solution, 60% diluent)
   • 80% dilution (80% stock solution, 20% diluent)
   • 100% dilution (100% diluent, 0% stock solution – this acts as a control).
3. Label five test tubes (or more, if repeating) corresponding to each dilution.
4. Add a fixed volume (e.g., $5\,\text{mL}$) of each prepared dilution to its respective test tube.
5. Add $1\,\text{mL}$ of 0.005% methylene blue solution to each test tube.
6. Gently shake each test tube to ensure the methylene blue is evenly distributed and the mixture is uniformly blue.
7. Place all test tubes simultaneously into a water bath maintained at a constant temperature (e.g., $37\,^{\circ}\text{C}$).
8. Immediately start a stopwatch for each test tube.
9. Observe and record the time (in minutes) taken for the methylene blue in each test tube to completely decolorize (turn colorless).
10. Repeat the experiment at least three times for each dilution to ensure reliability and calculate average decolorization times.

c) Record your results on the table below:

\begin{array}{|l|c|c|c|c|c|} \hline \text{% Dilution of stock} & 0\% & 20\% & 40\% & 80\% & 100\% \\ \hline \text{Time for decolorisation in minutes} & & & & & \\ \hline \end{array}