INVESTIGATING CATALASE IN LIVING TISSUES

 

bulletCatalase is an enzyme found in all living cells - this includes yeast!
bulletIt is responsible for breaking down harmful hydrogen peroxide (H2O2) into harmless water and oxygen.
bulletThe word equation for this is:

 

HYDROGEN PEROXIDE         CATALASE                      WATER + OXYGEN

                                                                                                                                   

 

bulletThe balanced symbol equation is:

 

 2H2O2                 CATALASE                                   2H2O  +  O2

           

 

 

bulletCatalase is the fastest known enzyme, with a ‘turnover rate’ of one million molecules of hydrogen peroxide per second!

 

bulletFor further information see: www.bbc.co.uk/schools/asguru

 

      SAFETY GOGGLES / SPECS WORN AT ALL TIMES

                        PLACE ALL SOLIDS IN THE BIN, NOT DOWN THE SINK

 

METHOD

 

  1. First, confirm that the reaction detailed above actually occurs:
    2. bulletPlace 1cm3  of hydrogen peroxide in a test tube (CARE!), then add 1cm3 of yeast solution.
    bulletPlace a glowing splint into the froth that forms – it should relight, a test for oxygen.

 

  1. Now observe the effect of different types of tissue on H2O2.
    2. bulletAdd 1cm3 of hydrogen peroxide to each tube and compare the maximum heights that the froth rises to.
    bulletWhat is the control?
    bulletYou should see that ALL tissue contains catalase.

 

Table of results:

 

Tissue Type

Height of froth (cm)

YEAST

 

POTATO

 

LIVER

 

INERT

 

 

 

 

 

  1. Compare the effect of surface area of exposed tissue.
    2. bulletSet up 2 test tubes with 1cm3 of H2O2 in each…
    bulletInto the first add a cube of liver, into the second add the equivalent volume of liquidised liver. What do you observe?

 

Table of results:

Surface area

Height of froth (cm)

Whole (low )

 

Liquidised (high)

 

 

 

  1. Investigate what happens when you change the concentration of the H2O2.
    2. bulletSet up 3 test tubes: one containing 1cm3 of plain water, a second containing 0.5 cm3 water + 0.5 cm3 H2O2 (i.e. a 50% mix), and a third containing 1cm3 full strength H2O2.

 

    bulletAdd 1cm3 of yeast solution to each tube and record the height of froth in each.

 

Table of results:

H2O2 conc. (%)

Height of froth (cm)

0 (water)

 

5

 

10

 

 

ANSWER THESE QUESTIONS IN YOUR NOTE BOOK:

 

a)      Give two reasons why measuring the height of froth is not a good dependent variable.

b)      Suggest a better, more accurate way that the rate of oxygen production could be measured (i.e. the volume of oxygen produced in a given time)

c)      State, or draw, what extra piece(s) of apparatus you would need.

d)      Which type of tissue used above, would be the most appropriate for a full investigation? Justify your reasons (i.e.‘say why’).

e)      Which of the 4 investigations would lend itself best to a ‘range of 5 or more readings’ (P.6b) for your independent variable? Again, justify your reasoning.

f)        Copy the diagrams into your book and then add the appropriate labels from the list below

 

 

 

 

                                                                                               

 

Key words: hydrogen peroxide       water        oxygen        substrate      products    yeast cells    catalase enzyme secreted          catalase enzyme unchanged