Enzyme-controlled reactions

• How can the rate of an enzyme-controlled reaction be measured?

  By measuring product appearance over time
• What enzyme is used in the breakdown of hydrogen peroxide?

  Catalase
• What happens to the oxygen released in the experiment with catalase?

  It displaces water from the measuring cylinder
• What is the purpose of the water bath in the experiment?

  To maintain different temperatures
• How long should you wait before measuring the reaction rate?

  5 minutes
• How is the mean volume of oxygen produced calculated?

  By averaging results from three trials
• What is the formula to calculate the mean rate of reaction?

  Mean rate = volume of oxygen / time
• What does amylase catalyse the breakdown of?

  Starch to maltose
• How can you test for the presence of starch in a solution?

  Using iodine in potassium iodide solution
• What color indicates the presence of starch when iodine is added?

  Dark blue-black
• How do you determine the speed of amylase activity in the experiment?

  By timing how long until iodine remains brown
• What should be done to ensure accurate results in enzyme experiments?

  Repeat the experiment three times
• What variables can be altered in enzyme experiments?

  • Temperature
  • Enzyme concentration
  • pH
  • Substrate concentration
• What is the key principle when changing variables in enzyme experiments?

  Only change one variable at a time
• How can the initial rate of reaction be estimated from a graph?

  By drawing a tangent at t = 0
• What is the formula for calculating the gradient of a tangent?

  Gradient = change in y / change in x
• How do you determine the units of the rate from a graph?

  By dividing y-axis units by x-axis units
• What is the initial rate of reaction?

  The rate at the start of the reaction
• What is the purpose of using a ruler when drawing a tangent?

  To ensure the tangent is straight
• Why is it important to estimate the initial rate of reaction?

  It provides insight into enzyme efficiency