Lipase and Milk Decay Experiment

Dr. Chip from Mastery Science presents a biology practical on decay, focusing on how temperature affects the rate of decay. The experiment uses milk, sodium carbonate, and phenolphthalein to observe color changes as decay progresses. Lipase is added to simulate microbial enzyme activity, and the time for decolorization is measured at various temperatures. Results are analyzed to understand the relationship between temperature and decay rate, with optimal enzyme activity expected between 30 and 45 degrees Celsius.

What is the independent variable in the decay practical?

• Amount of sodium carbonate

• Type of milk used

• Temperature

• Volume of phenolphthalein

Why is sodium carbonate added to the milk?

• To make the solution acidic

• To change the color of the milk

• To ensure the solution is alkaline

• To neutralize the milk

What color does phenolphthalein turn in an alkaline solution?

• Green

• Blue

• Pinky purple

• Yellow

What is the role of lipase in the experiment?

• To act as a control variable

• To measure the temperature

• To break down lipids in the milk

• To change the color of phenolphthalein

Why is it important to equilibrate the temperature of the milk and lipase mixture?

• To maintain the color of phenolphthalein

• To prevent the milk from spoiling

• To keep the lipase inactive

• To ensure accurate measurement of decay rate

What causes the milk to become more acidic during decay?

• Breakdown of lipids into glycerol and fatty acids

• Increase in temperature

• Presence of phenolphthalein

• Addition of sodium carbonate

What is the purpose of using lipase instead of microbes in this experiment?

• To avoid using chemicals

• To reduce the cost of the experiment

• To make the experiment more complex

• To speed up the experiment

At which temperature range is the lowest time reading expected for the decay process?

• 45 to 60 degrees Celsius

• 30 to 45 degrees Celsius

• 15 to 30 degrees Celsius

• 60 to 75 degrees Celsius

What is plotted on the x-axis of the graph in this experiment?

• Volume of lipase

• Temperature

• pH level

• Time

What is the optimal temperature for lipase activity in this experiment?

• 15 degrees Celsius

• 75 degrees Celsius

• 37 degrees Celsius

• 60 degrees Celsius