The Effects of Heat on Enzyme Reactions

The reactions of enzymes will be effected by heat, causing them to speed up, and eventually denature.


Will application of heat effect and/or change enzymes and their reactions with substrates?

Background Information

In order for the human body to function properly, energy molecules, or ATP, must be made by the body. The molecule used for making ATP is glucose. Glucose is a carbohydrate, usually found in the form of a disaccharide, and therefore must be broken down from a disaccharide to a monosaccharide. For this to happen, energy must be used to make a chemical reaction must take place. Heat is a factor that can help speed reactions up, but the body is too sensitive for high amounts of heat. In lieu of this, the body has catalysts, referred to as enzymes, which help lower the energy hill that substrates like lactose and other disaccharides have to climb. So it is only logical that when heat is applied to an enzyme, they should increase the speed at which they perform reaction, but if exposed to excessively high temperatures, should become denatured and useless.

As stated before, enzymes are used to break down substrates, with the help of hydrolysis, or addition of H2O. They can also build up substrates into bigger products through the process of dehydration synthesis, or removal of H2O. Although enzymes can be used unlimitedly until denatured, most can perform only one specific reaction. For instance, the enzyme lactase only works to break down lactose into glucose and galactose. To perform reactions, enzymes either fit with a substrate the way a lock and key do, or they mold to make an induced fit around the substrate. Then in the active site, the reaction occurs, and the substrate is ejected as either one of two products. In our experiment, we plan to test the amount of glucose produced through this process when certain factors are affecting the enzyme used.

There are four factors in the body that affect enzyme reactions. One of these is pH, which reflects how acidic or basic a substance is, and is caused excessiveness of H+ or OH- in the substance. Most enzymes are set to work at a specific pH, and if at the wrong pH, can be changed and denatured. Another factor affecting enzymes is heat, or temperature, which is what we plan to be testing. As you read before, temperature affects enzymes by speeding them up, or slowing them down, and if exposed to excessive heat, enzymes will also denature. The third factor that enzymes are affected by is the speed of enzymes. As an enzyme speeds up, the molecules its made of also speed up and bump into each other, which after time can cause the enzymes to become denatured. The fourth and final factor of enzymes is the amount of substrate. Enzymes have to adapt their rate of reactions when different amounts of substrate are being processed.

  1. Procedure:
    1. Material List:
      • 4 Beakers
      • 1 Test tube
      • 1 Hot plate
      • 10 mL lactase solution
      • 20 mL lactose solution (nonfat-milk)
      • 2 goggles
      • 1 clock/stopwatch
      • 7 glucose test strips
      • 1 stirring rod
      • 1 10 mL graduated cylinder
      • water
    2. Methods:
      1. Gather all materials
        1. Put on goggles
        2. Fill one beaker with 10 mL lactase solution
        3. Fill one beaker with 20 mL lactose solution
        4. Fill one beaker with 100 mL water
        5. Turn hot plate on to low setting
        6. Using the 10 mL graduated cylinder, measure out 1mL of lactase into test tube
        7. Set test tube in beaker containing water, then set beaker on hot plate
        8. Using the clock or stopwatch, wait 5 minutes before removing the test tube from water
        9. In final beaker, mix heated enzyme with 2 mL of lactose solution
        10. Set 1 glucose test strip into new solution
        11. After 2 timed minutes, remove test strip and record color of strip
        12. Repeat steps 7-12 for the 3, 5, and high settings on hotplate
        13. Clean out test tube, beakers, and graduated cylinder, and put away materials
  2. Safety:
    1. Practice proper heat and fire precautions
      1. Keep goggles on throughout experiment
        1. Use caution when handling glass instruments
        2. Don’t ingest any of the solutions

V. Data Collection and Presentation:

A) Diagrams

B) Data Table

Heat Setting Glucose Level
1(Low) Light Green
3 Light Green
5 Light Green
7(High) Light Green
  1. Graph

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