Investigate the effect of enzyme concentration on the activity of catalase in potato tuber cells on hydrogen peroxide measuring the time taken to produce 5 ml of oxygen produced to determine the rate of reaction.

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Aim: -

        To investigate the effect of enzyme concentration on the activity of catalase in potato tuber cells on hydrogen peroxide measuring the time taken to produce 5 ml of oxygen produced to determine the rate of reaction.

Method: -

  1. Set up apparatus as shown in the diagram below.

  1. Using the measuring cylinder add 50 cm3 20vol. hydrogen peroxide solution into the conical flask.

  1. Use the cork borer to bore several cylinders from the potato all of equal thickness.  Cut the potato cylinders into a length of 4 cm (ensure there is no potato skin present).  You will need to cut 45 potato cylinders in total.  Make sure you cut all the potato cylinders with the same cork borer and measure the diameter of the potato cylinder to work out the surface area.

  1. Ensure your apparatus is set up correctly, that the graduated cylinder is inverted and full of water and placed over the end of the rubber tubing, and your stopwatch and table are ready to record your results.

  1. Place one cylinder of potato into the conical flask containing hydrogen peroxide and immediately seal the top tightly with the rubber bung.

  1. Holding the graduated cylinder vertically, record the time it takes for 5ml of water to be displaced from the inverted measuring cylinder by the oxygen produced.  Only start your stopwatch when the first bubbles appear in the cylinder.

  1. Repeat the experiment an additional potato cylinder to the flask each time until 5 cylinders have been used at once.  Use fresh hydrogen peroxide each time.

  1. Repeat the whole experiment 3 times.            

Apparatus: -

Safety: -

        When using scalpel and cork borer you need to take care.  Hydrogen peroxide is an oxidant, and needs to be kept away from heat.  It can be an irritant or corrosive at strong concentrations, so care is needed with the 20vol.  Avoid contact with skin.  Safety glasses and lab coat should be worn and contact of hydrogen peroxide with the skin should be avoided (gloves should be worn.

Results: -

A table to show the rate of reaction for catalase in potato with hydrogen peroxide when amount of catalase is increased as an increase in number of potato sticks:

Diameter of potato cylinder = 1.2cm

Surface area of 1 potato piece = πr2 + πr2 + (4 x πD)

D= 1.2 cm                                            = π0.62 + π0.62 + (4 x π x 1.2)

r = 0.6 cm                                              = 17.342 cm2

                                              = 17.34 cm2

I am working out the surface area of the potato because it is directly proportional to the amount of enzyme in contact with the substrate (H2O2) and therefore is a good measure of the enzyme concentration.

(Look at graph paper for two plotted graphs)

Analysis of results: -

        

        From my results I plotted two graphs the first was the rate of reaction against surface area of potato and the other was average time taken against surface area of potato.  I am going to explain the graphs separately.


Rate of reaction graph:

        From the graph you can see that as the surface area/number of potatoes increases so does the rate of reaction.  For example the rate of reaction for 1 potato or for the surface area of 1 potato is 0.05 (ml sec-1) and for 2 potatoes it is 0.13 (ml sec-1).  This shows that the rate of reaction has more than doubled from 1 to 2 potato pieces.  For 4 potatoes the rate of reaction is 0.34 (ml sec-1) this shows that from 2 to 4 potatoes the rate of reaction has nearly trebled.  The slowest rate of reaction is for 1 potato the fastest is for 5 potatoes and its rate of reaction is 0.47 (ml sec-1).  The increase in rate was fastest between 3 and 4 potato pieces and the slowest increase in rate was between 2 and 3 potato pieces.

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Average time graph:      

        From this graph you can see that as the surface area/number of potatoes increases the average time taken to produce 5 ml O2 decreases.  For example the average time taken for 1 potato is 98 seconds but for 2 potatoes it is 39.33 seconds.  This shows a significant decline in the average time taken from 1 to 2 potato pieces.  The longest average time taken is for 1 potato and the quickest is for 5 potatoes which is 10.67 (sec).

Conclusion: -

        From my results you can see that ...

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