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 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 our 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.The substrate is the reactant of an enzyme-catalyzed reaction. 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. Hydrogen peroxide 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 catalase2H2O + O2 + heat

hydrogen peroxide water oxygen

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

Prelab:

Tech Talk: You should know the meaning of the following terms

Catalase-

Enzyme-

Substrate-

Hydrogen peroxide-

Catalyst-

Objectives: Design an experiment to show how an enzyme affects a chemical reaction. Possible Outcomes

  • Observe the reaction of catalase with hydrogen peroxide
  • Compare the activity of catalase in animal cells and plant cells.
  • Infer the effect of heating or cooling on the rate of reaction when using an enzyme
  • Infer the effect of concentration on the rate of reaction when using an enzyme
  • Create a lab report using the scientific method.

Available Materials:

water soluble marker

5 - test tubes

test-tube rack

100 ml graduated cylinder

10 ml graduated cylinder

paper towel

forceps

test tube brush

sludge bucket

Choose one of the procedures below to observe how an enzyme affects the reaction on a substrate. Circle the experiment that you would like to design, perform and then write up in a

lab report.

Procedure:

Part A: Type of Food

  1. Label the five test tubes as follows: Hamburger, spinach, raw liver, potato.
  2. Measure 20 ml of hydrogen peroxide solution into the 100 ml graduated cylinder. Use the 10 ml

graduated cylinder to pour 2 ml of hydrogen peroxide into each test tube.

  1. Using a wooden splint, take a drop of spinach, hamburger, raw liver, potato, and chalk. Be sure to

get about the same amount of each item. NOTE: Remember to use the appropriate splint for

each sample as to not cross contaminate the samples.

  1. Place each item into the appropriately labeled test tube.
  2. Observe the reaction in each test tube. Note the speed at which each test tube is bubbling

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 may feel. List the food in terms of their reaction speed on your data sheet.

  1. Clean up by putting contents of test tubes into the waste containers and rinse the test tubes

Part B: Amount of Food

  1. Label two test tubes: One and two
  2. Use the cylinder to pour 2 ml of hydrogen peroxide into each test tube.
  3. Obtain 3 small and equal drops of raw liver.
  4. Place one piece of liver into test tube one and two pieces of liver into test tube two.

5. Observe the reaction in each test tube. Note the speed at which each test tube is bubbling and at the same time compare the warmth of each of the tubes.

6. Clean up by putting contents of test tubes into the waste containers and rinse the test tubes

Part C: Temperature of Food

  1. Label two test tubes: room temp and cold
  2. Use the graduated cylinder to pour 2 ml of hydrogen peroxide into the room temp test tube.
  3. Use the graduated cylinder to get 2 ml of cold hydrogen peroxide from the cold water bath and put it into the cold test tube.
  4. Obtain small and equal amounts of raw liver.
  5. Use the splint, place one piece of liver into each test tube.
  6. Observe the reaction in each test tube. Note the speed at which each test tube is bubbling and at the same time compare the warmth of each of the tubes.

7. Clean up by putting contents of test tubes into the waste containers and rinse the test tubes

Use the Sample Lab Report Form to write up a lab report for your experiment. You should create a data table to collect results and then graph any results you get from the experiment. Use the Sample Lab Report form to guide you as you write a conclusion and evaluation for your experiment.

Lab Report Form:______Name: ______

Purpose:

Variables

  • Independent/Manipulating Variable:
  • Dependent/Responding Variable:
  • Controlled Variables:

Hypothesis:

Materials :

Procedure: In your own words

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7.

Safety:

Data and Analysis

  • Table of results
  • Graph(s) of relevant results
  • Describe trends/patterns in the data

Conclusion:

Evaluation: