enzyme and substrate concentrations

• IV


  Protease concentration (measured in percentage)
• DV


  Time taken for enzyme to breakdown substrate (in seconds)
• cvs

  • Temperature – measure temperature of water bath with thermometer and make sure it is constant for repeats
  • Volume of enzyme solution – 2 cm³ of the protease enzyme solution will be used each time
  • Volume of substrate – 5 cm³ of casein solution will be used each time
• control


  Enzyme concentration of 0.0%  (distilled water) can be used and added to the casein solution. Results can be compared to this control result.
• enzyme concentration.

  • Enzyme concentration affects the rate of reaction
  • The higher the enzyme concentration in a reaction mixture, the greater the number of active sites available and the greater the likelihood of enzyme-substrate complex formation
  • As long as there is sufficient substrate available, the initial rate of reaction increases linearly with enzyme concentration
  • If the amount of substrate is limited, at a certain point any further increase in enzyme concentration will not increase the reaction rate as the amount of substrate becomes a limiting factor
• substrate concentration

  • Substrate concentration affects the rate of reaction
  • The higher the substrate concentration the faster the rate of reaction
  • More substrate molecules means more collision between enzyme and substrate so the more likely an active site will be used by a substrate
  • The is only the case up until a certain concentration of substrate,
  • At this point all active sites are occupied and increasing the substrate concentration will not affect the rate of the reaction
• 2 ways to measure rate of reaction

  • Measure how fast the product is made
  • Measure how fast the substrate is used up
• common enzymes used


   catalase, amylase and protease
• initial rate of reaction

  • The initial rate of reaction is at the start of the reaction
  • You can calculate the initial rate of reaction using a graph of results showing volume of product/substrate against time
  • Draw a tangent to the graph through the origin 
  • Calculate the gradient of the tangent - this is the initial rate of reaction
• method part 1

  1. Add a set volume of hydrogen peroxide solution to a boiling tube
  2. Add a set volume of buffer solution to the same boiling tube
  3. Invert a full measuring cylinder into a trough of water
  4. Place the end of the delivery tube into the open end of the measuring cylinder and attach the other end to a bung
  5. Add a set volume of one concentration of catalase to the boiling tube and quickly place the bung into the boiling tube
  6. Record the volume of oxygen collected in the measuring cylinder by the water displaced every 10 seconds for 60 seconds
• method part 2

  • Repeat the experiment twice more and calculate the average volume of oxygen produced at each 10 second interval
  • Repeat the whole experiment for the different concentrations of catalase
  • Plot the average volume of gas produced against time for each concentration
  • Compare the initial rate of reaction of each of the concentrations
• results

  • As the concentration of catalase increases the volume of oxygen produced would increase
  • This is because there would be more available active sites for hydrogen peroxide to use
  • The volume of oxygen would plateau out after the initial rate of reaction due to the substrate decreasing, having been converted into the product (oxygen)