Enzymes are used in all metabolic reactions to control the rate of reactions and decrease the amount of energy necessary for the reaction to take place. Enzymes are specific for each reaction and are reusable. Enzymes have an area called the active site to which a specific substrate will bond temporarily while the reaction is taking place. Enzymes are proteins that are used as catalysts in biochemical reactions. A catalyst is a factor that controls the rate of a reaction without itself being used up. In biological systems, enzymes are used to speed up the rate of a reaction. However, there are a number of factors that can affect the rate of an enzyme-facilitated reaction, in addition to the presence of the enzyme, amongst them are:
Here is a set of quick activities designed to simulate how substrate concentration and temperature affect enzyme function. In the activities that follow:
Toothpickase is a DIGESTIVE ENZYME. It breaks down toothpicks into two units. To hydrolyse the toothpick, place a toothpick between the thumb and the first finger of each hand. Break the toothpick in two pieces.
Here are the rules:
1. You must break each toothpick one at a time.
2. You must break each toothpick completely in half.
3. You cannot begin early and must stop precisely when told to do so.
4. You must keep your eyes closed throughout the entire activity.
In this activity, the toothpicks represent a substrate and your thumbs and index fingers represent the enzyme, toothpick-ase. When you break a toothpick, the place where the toothpick fits between your fingers represents the active site of the enzyme.
1. Count out 100 unbroken toothpicks into a bowl on your desk.
2. The person acting as the enzyme is to break toothpicks without looking at the bowl and all of its products (broken toothpicks). All broken toothpicks must remain in the bowl along with the unbroken toothpicks,& you cannot re-break a broken toothpick!.
3. The experiment is conducted in 10 second intervals.
4. WITHOUT LOOKING AT THE BOWL, break as many toothpicks as you can in 10 second intervals. Broken toothpicks should be kept in the bowl with unbroken toothpicks because products & reactants mix in metabolic reactions. DO NOT BREAK TOOTHPICKS ALREADY BROKEN!
6. Do another 10 seconds of breaking (total of 20 seconds now), and then count & record the number of toothpicks broken.
7. Do another 10 seconds (thirty seconds total now) more of breaking and count and record the number of toothpicks broken.
8. Continue breaking toothpicks for these total time intervals (60 and 120 seconds). REMEMBER TO ALWAYS THROW BROKEN TOOTHPICKS BACK IN THE PILE (because products & reactants stay mixed in reactions), BUT DON’T RE-BREAK THEM (the enzyme has already acted on the substrate!
PART B: EFFECT OF SUBSTRATE CONCENTRATION ON REACTION RATE
Materials: 1 box toothpicks per team
100 paper clips
clock/watch with a second hand
Remove the broken toothpicks from the shallow bowl. Place 100 paperclips in the empty 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.
For the first trial, place 10 toothpicks in the bowl with the paper clip. Mix them up. The enzyme has 20 seconds to react (break as many toothpicks as possible). Remember the enzyme breaks the toothpicks without looking at the bowl and all of the products (“broken toothpicks”) must remain in the bowl. Remember toothpicks can only be digested once; do not break toothpicks already broken! Record the number broken at a concentration of 10.
Remove the broken toothpicks and repeat with concentrations of 20, 30, 40, 50, 60, 70, 80, 90, and 100 toothpicks, each time mixing them with the 100 paper clips.
PART C: EFFECT OF TEMPERATURE SUBSTRATE CONCENTRATION ON REACTION RATE
Materials: 10 toothpicks per team
ice & ice bucket
clock/watch with a second hand
Select 10 toothpicks. Time how long it takes to break the 10 toothpicks as fast as you can.
Place your hands in the pail of iced water for 10 minutes. Repeat step 1.
Calculate the rate of enzyme action in toothpicks per second. Compare the two rates.
Analysis and Conclusion:
Complete your Lab by creating a graph and answer the questions. REMEMBER THE HIGHEST GRADE POSSIBLE IF YOU DO NOT COMPLETE THE GRAPH AND QUESTIONS IS A D.