Investigating enzymatic reactions

• What enzyme catalyses the breakdown of starch to maltose?


  Amylase
• How can you detect the presence of starch in a solution?

  Using iodine solution, which changes from browny-orange to blue-black
• What is the procedure to investigate how pH affects amylase activity?


  1. Add iodine solution to a spotting tile.
  2. Heat water to 35 °C in a beaker.
  3. Mix amylase and buffer solution in a boiling tube.
  4. Add starch solution and start timing.
  5. Sample every 30 seconds until starch is gone.
  6. Repeat with different pH buffers.
  7. Control variables for a fair test.
• What temperature should the water be heated to in the experiment?


  35 °C
• Why is it important to keep the temperature constant during the experiment?


  To ensure that temperature does not affect enzyme activity
• What is the volume of amylase solution added to the boiling tube?


  1 cm³
• What is the volume of buffer solution used in the experiment?


  1 cm³
• What does continuous sampling involve in this experiment?


  Taking a fresh sample every 30 seconds to check for starch
• What indicates that starch is no longer present in the solution?


  When the iodine solution remains browny-orange
• How do you calculate the rate of reaction in the amylase experiment?


  • Rate = 1000 / time
  • Example: If time = 90 seconds, then Rate = 1000 ÷ 90 = 11.1 cm³ s⁻¹
• What is the formula to calculate the rate of reaction?


  Rate = 1000 / time
• If the time taken for amylase to break down starch at pH 6 is 90 seconds, what is the rate of reaction?


  11.1 cm³ s⁻¹
• What does the rate of reaction measure?


  How much something changes over time
• How would you calculate the rate of reaction if 24 cm³ of oxygen was released in 50 seconds?


  Rate = 24 cm³ ÷ 50 s = 0.48 cm³ s⁻¹
• What other factors can be investigated to affect the rate of amylase activity?


  • Temperature
  • Concentration of substrate
  • Concentration of enzyme
• What is the product formed when catalase breaks down hydrogen peroxide?


  Water and oxygen
• If an enzyme-controlled reaction was carried out at pH 4 and 36 cm³ of product was released in 2 minutes, what is the rate of reaction?


  18 cm³/s
• How do you calculate the rate of reaction for the given example of 36 cm³ in 2 minutes?


  Rate = 36 cm³ ÷ 120 s = 0.3 cm³ s⁻¹