Class Copy


Source: National Health Museum Access Excellence.


Enzymes are proteins that are used as catalysts in biochemical reactions. A catalyst is something that controls the rate of a reaction without itself being used up. Often enzymes are used to speed up the rate of a reaction. However, there are at least two things that can affect the rate of a reaction: 1) substrate formation, and 2) temperature. Here is a set of activities designed to simulate how substrate concentration and temperature affect enzyme function. In those activities that follow:


Part A: Rate Of Product Formation

  1. Select 80 toothpicks and place them in a shallow bowl.
  2. In your group of three, one person will be the timer, one will record the data, and the third person will be the enzyme, toothpickase. The enzyme is to break the toothpicks without looking and all of the products ("broken toothpicks") must remain in the bowl.
  3. The experiment is conducted in 20 second intervals. The timer calls out start and then marks each 20 second interval. The recorder tallies the cumulative number of toothpicks broken as each interval is announced by the timer.
  4. Graph the results plotting Product Formed (the total number of toothpicks broken) vs. Time (20s, 40s, 60s, 80s...). Calculate the rate of enzyme action in toothpicks per second for each 60s interval, eg.) How many toothpicks were broken after 1 minute, 2 minutes, 3 minutes, etc. Do not forget to title your graph and each member of the group must make a graph, not just the recorder.

Part B: Reaction Rate Vs. Substrate Concentration

  1. Remove the broken toothpicks from the shallow bowl. Place 80 paperclips in the bowl. The paper clips represent a "solvent" in which the toothpicks are "dissolved". Different concentrations are simulated by mixing different numbers of toothpicks in with the paper clips.
  2. For the first trial, place 10 toothpicks in the bowl with the paper clip. The enzyme has 20 seconds to react (break as many toothpicks as possible). Record the number broken at a concentration of 10.
  3. Remove the broken toothpicks and repeat with concentrations of 20, 30, 40, etc. up to 100 toothpicks (ie. generate 10 data points).
  4. Graph the results by plotting Reaction Rate (toothpicks broken in 20 seconds) vs. Substrate Concentration (10, 20, 30, 40 ... 100). Do not forget to title your graph. Each member of the group must do this, not just the recorder.

Part C: Reaction Rate Vs. Temperature

  1. Select 10 toothpicks. Time how long it takes to break the 10 toothpicks as fast as you can.
  2. Place your hands in the pail of iced water for 10 minutes.
  3. Repeat step 1.
  4. Calculate the rate of enzyme action in toothpicks per second. Compare the two rates. Write up an explanation as to what happened and why it happened.
  5. Clean up your work bench.
  6. Before handing in you lab write-up, ensure that you have:
    1. included a proper title for each graph, and labelled both the x and y axis
    2. answered the question in Step 4 (Part A) and Step 4 (Part C)
    3. put your name on each page that will be handed in.