Measuring Enzyme Activity

• Measuring Enzyme Activity


  1. Measuring the rate of formation of a product

  2. Measuring the rate of disappearance of a substrate

  3. Investigating catalase activity
• Hydrogen peroxide


  A common but toxic by-product of metabolism that must be broken down quickly
• Catalase


  An enzyme found in the cells of most organisms that breaks down hydrogen peroxide into water and oxygen
• Investigating catalase activity


  1. Hydrogen peroxide and catalase are combined

  2. The volume of oxygen generated is measured in a set time

  3. The rate of reaction can then be calculated
• Investigating amylase activity using iodine

  1. Amylase and starch are combined

  2. Reaction mixture is tested for starch at regular time intervals

  3. Samples are added to iodine in potassium iodide solution

  4. Time taken for starch to be broken down is measured
• Amylase


  • A digestive enzyme that hydrolyses starch into maltose and glucose
  • Functions best at pH 7 and 37°C
• Investigating the effect of starch concentration on amylase activity using colorimetry

  1. Colorimeter calibration

  2. Preparation of a starch solution of known concentration

  3. Measuring percentage absorbance or percentage transmission values

  4. Plotting a calibration graph of starch concentration vs percentage absorbance or percentage transmission
• Colorimetry can be used in any enzyme-catalysed reaction that involves colour change
• As the colour breaks down the transmission increases or light absorption decreases and this can be used to measure the rate of the reaction