NAME:______PERIOD:_____DATE:______

Lab: Catalysts of Life

Introduction:

Hundreds of chemical reactions take place in your cells. For example, chemical reactions are needed to break down food and release energy, to form new molecules, and to produce new cells. All of these reactions require protein molecules called enzymes. An enzyme is a catalyst. A catalyst speeds up a chemical reaction but is not used up or changed by the reaction. Without the help of enzymes, the chemical reactions in your cells would take place too slowly.

A specific enzyme is required for each step of a chemical reaction. The shape of the enzyme enables it to “fit” with a particular substance, called the substrate. In this lab you will observe the action of the enzyme catalase, derived from foodstuffs, on its substrate, hydrogen peroxide.

You may have used hydrogen peroxide to clean a wound or as a bleaching agent. This chemical is sometimes produced in cells during cellular respiration. Catalase then breaks down the hydrogen peroxide into oxygen and water, as shown in the following equation:

2H2O2 catalase 2H2O + O2 + heat

hydrogen peroxide water oxygen

If hydrogen peroxide were not immediately broken down by catalase, it would damage the cell.

Objectives:

Observe the reaction of catalase with hydrogen peroxide.

Compare the activity of catalase in animal cells and plant cells.

Infer the effect of boiling enzymes.

Materials:

7 test tubesraw hamburger

test-tube rackfresh spinach leaf

3% hydrogen peroxide solutionraw liver

100ml graduated cylinderpotato

platechalk

scalpelcracker

forcepsboiled liver

Procedure:

Part A
  1. Formulate a hypothesis about which enzyme source will have the fastest reaction with the hydrogen peroxide and the slowest reaction and why for both.
  2. Use the masking tape and sharpie to label the 7 test tubes with the 7 enzyme sources.
  3. Have one person in your group come up and get 14 ml of hydrogen peroxide solution into the graduated cylinder. Use the graduated cylinder to pour 2 ml of hydrogen peroxide into each test tube.
  4. Have the other person come up to the front desk and using different scalpels; carefully slice off a piece of each of the enzyme sources (spinach, raw liver, hamburger, potato, cracker, chalk and boiled liver).
  5. Place the items on a paper towel, but keep all the items separate.
  6. Use your fingers or forceps to gently pick up each of the possible enzyme sources from the paper towel and place each item into the appropriately labeled test tube.
  7. Observe the reaction in each test tube. Note how rapidly each test tube is bubbling and at the same time compare the warmth of each of the tubes. The faster the chemical reaction, the more forcefully the liquid bubbles and the warmer the test tube feels.
  8. List the possible enzyme sources in terms of their reaction speed in the data table.

Hypothesis:

Data Table:

Enzyme Source / Amount of Reaction
/ Most Reaction
Least or no Reaction

Analyses and Conclusions:

  1. Evaluate your hypothesis. What evidence do you have that supports or rejects your hypothesis? If your hypothesis was incorrect, how could you restate it?
  1. Explain why the test tubes felt warm.
  1. Describe the difference in reaction you observed between the boiled and raw liver.
  1. Identify which of the substances that you tested in contained the most catalase. Explain.
  1. Did any of the substances not produce a reaction? Explain why or why not.
  1. What might you hypothesize about the amount of catalase in animals and plants?
  1. What can you infer about the effect of boiling enzymes, based on your observations?
  1. What is the purpose of enzymes in a living system?
  1. What do you think would happen to the enzyme if the pH is changed? Explain.
  1. What do you think would happen if there were no enzymes?

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