Monday, March 5, 2012

Easy Enzyme Experiment: Potato Catalase


Catalase enzyme formed the bubbles in the two tubes on the right.  The tubes contain extracts from beef muscle, kidney, and liver from left to right. 
In a post awhile back we discussed the enzyme catalase and its presence in animal tissues such as liver, kidney, and muscle.  Catalase was and is found to be extremely abundant in the liver, a reflection of the livers cleansing function.  It is also present, but much less so, in the kidneys, also a reflection cleansing function.  Muscle tissue however had no detectable catalase due to the fact that it is not a cleansing organ, waste products from the muscles are rather filtered and cleaned by the liver and kidneys.  Catalase also has been found in plants, where its presence is often mysterious.  Plants of course are not producing waste products similar to what animals produce, so why would they need catalase?  We can discover the answer partially by simply understanding the function of catalase.
This is what catalase does in general:
Hydrogen Peroxide + Catalase → Water and Oxygen

Hydrogen peroxide is a highly oxidative molecule, meaning it causes processes similar to rusting to occur.  Metals rust as they react with oxygen and oxidative molecules cause rusting to occur.  Similar “rusting” or oxidative reactions can occur in plant or animal tissues if oxidative molecules are present.  This is why anti-oxidants are such a big deal, they prevent tissue from oxidizing by getting rid of oxidizing molecules such as hydrogen peroxide.  Catalase is such an anti-oxidant molecule.  Catalase also converts reactive oxygen, which also oxidizes, into hydrogen peroxide and then into harmless water and oxygen.  (Of course I have simplified these reactions, so chemists, refrain from complaint!)  At the end of a reaction catalase is preserved and available to repeat the reaction over again with more oxidative molecules.  Amazingly, one catalase enzyme can repeat these reaction up to 40 million times in one second!
Another catalase reaction:
Reactive Oxygen + Catalase → Hydrogen Peroxide + Catalase → Water and Oxygen

In animals, such as us, oxidative molecules are most often produced through our metabolizing of food molecules.  So the presence of catalase makes sense.  Plants do not eat, so why would they need catalase?  If we study the process of photosynthesis we may come across a term called photorespiration.  Photorespiration simply is when a plant receives too much light and not enough water.  As a result, the plant can produce large amounts of hydrogen peroxide which can kill the plant.  Fortunatly, catalase prevents the accumulation of hydrogen peroxide by converting it to water and oxygen, and so saves the plant from oxidative damage.

A Simple Catalase Experiment Using Potatoes:
Some plants such as potato and spinach have very high levels of catalase, far higher they they would likely ever need to prevent photorespiration damage.  Why that is, no one seems to know. Scientists have had many ideas and have researched the question for almost 100 years but no one can figure it out.  But it makes isolating the catalase enzyme very inexpensive and easy if you want to run a simple experiment.  The following is a simple enzyme experiment anyone can run.
Materials:
Potato
Test tube or other small container
Hydrogen Peroxide

1. Cut up a potato and mash it.  Do not cook it, cooking will break down the enzyme so it won’t work.

2. Place the mashed potato in a test tube or other small container.

3.  Add hydrogen peroxide.  If there is catalase present foam should be produced.

The foam produced is a result of catalase converting hydrogen peroxide into water and oxygen, the bubbles are filled with this oxygen.  The more bubbles produced the faster catalase is carrying out this reaction, or the more catalase present.  The above would be considered the control for the experiment and simply indicated the presence of catalase in the potato.  Tests can be preformed to determine the effects of different conditions on the enzyme function.  By adding baking soda to the potato, a high pH or basic molecule, will change the pH and have an effect on how well catalase functions.  To another test tube, add vinegar to the potato which will lower the pH, making it acidic also having an effect.  Also try freezing or cooking the potato before adding hydrogen peroxide to determine effects.  Remember, the more foam produced the better the catalase enzyme is working.  Less foam means it is not working as well, and no foam means it is not working at all.  Test it out and see what you find.  
Potato catalase experiment.  The boiled tube (left) produced no bubbles indicating catalase has been degraded by the heat.  Room temperature tube (middle) produced the most bubbles indicating catalase is highly functional at this temperature.  The tube kept on ice (right) produced fewer bubbles indicating the lower temperature slowed down the catalase enzyme.

40 comments:

  1. Thank you so much, helped a lot in Biology

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  2. How much potato? How much peroxide? Into what size testube? I would like to run this for a class so Im trying to get all materials together. Also, can I simple grate the potatos ahead of time?

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    1. Begin with about 40 grams of peeled potato and blend it in about 100ml of water and ice. Mix this well and add 1 ml to a test tube. Test tubes of 10 to 15ml work well. Add several drops of H2O2 to the potato blend in the bottom of the test tube. Exact amounts do not matter, as long as they are relatively close. Yes, you can mash or blend potatoes ahead of time. Blending works best. I really don't know why I used the word "mash" in this post. Hope this helps. -Matt

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    2. Oh-ya, be sure to test this ahead of time and adjust volumes as necessary. The experiment works differently with different potatoes. Error on the side of more potatoes. More potato means more foam.

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  3. Thanks. I did a test run this morning with straight potato peelings.Slower reaction but good enough. Started with the liquids first and the dropped in the peels, followed by swirling of the tt to get them to the bottom.My peroxide might be a little dated but 3% and ten minures later the tots were being lifted out of the tubes!

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    1. Great! Thanks for letting me know. I never have tried it that way but it sounds extremely easy. I'll have to try your method sometime.

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  4. Hi, I have recently done an AS level catalase experiment. We cut out thin discs of potato and put them into a 10cm^3 solution of hydrogen peroxide then measured how long it takes for them to rise to the top. Our independent variable was different concentrations of hydrogen peroxide. Our results showed that as the concentration of H2O2 increased, the rate of reaction increased. I was wondering if you could explain the theory of this. Thanks!

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    1. The more substrate(H2O2) for the enzyme to react with the faster the reaction will take place. Higher concentration of H2O2 means there is more substrate for catalase to react with.

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  5. If you were to plan an experiment to determine the effect of substrate concentration on enzyme activity. What would you write as the method?

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    1. Simply vary the concentration of H2O2, which is the substrate. With store bought H2O2, vary the concentration by adding 100% of the H2O2 to potato extract, 75% H2O2, 50%, 25% and 0%, all to different tubes. Create these various H2O2 concentrations by mixing the H2O2 with water.

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  6. Which are the dependent, independent and controlled variables?

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    1. Dependent is always going to be bubbles produced when H2O2 is added.
      The independent variable depends on what type of experiment you are running, it could be H202 concentration, amount of potato, temperature, or pH.
      Control variables also depend on what type of experiment you are running.

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  7. what are the conclusion and discussion?

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    1. That entirely depends on how you carry out your experiment.

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  8. How much time is needed for this process to occur ?

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    1. The reaction happens instantly and only takes a few seconds.

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  9. LIFE SAVER!!! had to write a stupid report and didnt have any idea where to begin!

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  10. Hi Matt
    I'm just wondering are there any other conditions we can test on catalase. I mean instead of testing the usual temperature, pH and substrate concentration, are there other conditions that can be manipulated to produce an effect result?

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  11. Another condition you can modify is buffer concentration. This can be done simply by modifying NaCl concentration the substrate or enzyme is in.

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  12. Yo Matt help mout here why does the bubbles from the oxygen produce remain constant and decrease

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    1. Not sure what you mean exactly, but bubbles decrease as the substrate of H2O2 decreases.

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  13. What difference would you expect to see in the experiment using varying temperatures ?

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  14. This helped me quite a lot for a Biochemistry that I have to do for school. However, the information on altering the PH levels is rather limited. Would it be possible for you to recommend some online sight where I could find more information on this?
    Please and thank you in advance :)

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  15. hi sir/ma'am,
    do you mind writing down the materials needed for this experiment and how much is needed for the experiment for it to work effectively as i may be using this experiment for year 12 assessment and i want to make sure it works efficiently. thankyou soo much!

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  16. Hello, I am wondering if when adding the baking soda I also have to add some type of liquid to get a reaction. I already know that I'm going to add peroxide to one experiment but for the second one I would like to use baking soda. Let me know, thanks :)

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  17. Hi, can I ask something.. Is the rate of enzymatic reaction always directly dependent on the enzymatic concentration? Thank you so much :D

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    1. Yes it is, although can also be directly dependent on the temperature of the enzyme and the pH level :)

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  18. The results are not able to be measured are they? I need results involving numbers but I really liked the experiment. Is there any way I could do it?

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  19. Did you have any sources of error?

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  20. hey can you tell me some things that i can put in my discussion?

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  21. What are the manipulated results?

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  22. Hello! I just want to thank you for uploading this, im supposed to do the lab tomorrow however my teacher refused to help me in any sort of way so thank so much! :D

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  23. You know PHEOC? What's the 'Problem' for this lab?

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  24. please really want to know the enzymes reaction on prepared potato

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  25. why blend the potato? is potato not uniform throughout?

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  26. What happens if you add Meat or Something else

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  27. This was quite informative :-)

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  28. Ayanna, Mickeisha thought that this was not as informative

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