Enzyme-controlled reactions

• What happens to a substrate molecule in an enzyme-controlled reaction?

  It is converted into a product molecule
• What must happen for a substrate molecule to be converted into a product molecule?

  The substrate molecule must collide successfully with the active site of the enzyme
• What does a steep line on a graph of product formation indicate?

  • A large amount of product is produced in a short time
  • The rate of reaction is rapid initially
• What does it mean when the line on the graph becomes less steep during the reaction?

  The amount of product being formed in a given time is less than at the start
• What does a horizontal line on the graph indicate about the reaction?

  No more product is being made, so the reaction has stopped
• How can we measure the rate of an enzyme-controlled reaction at any point?

  • By drawing a tangent to the curve at the point of interest
  • The tangent is a straight line that touches the curve
• How do you calculate the gradient of the tangent to find the rate of reaction?

  By dividing the vertical side (y) by the horizontal side (x)
• Why should a tangent line be reasonably long when measuring the rate of reaction?

  It makes it easier to read the numbers accurately
• What factors affect the rate of an enzyme-controlled reaction?

  • Frequency of successful collisions between substrate and active site
  • Amount of substrate available
  • Concentration of the enzyme
• What happens to the frequency of successful collisions as the reaction proceeds?

  It decreases as the amount of substrate molecules falls
• What happens when all substrate molecules have been converted to product?

  The reaction stops