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The Effect of Hydrogen Peroxide on Potatoes

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The Effect of Hydrogen Peroxide on Potatoes

Experiment to find out the effect of hydrogen peroxide on potatoes and
to see if the surface area affects the amount of froth produced


(Sources: Internet, Biology Book, Chapter on Enzymes)

Enzymes such as catalase are protein molecules, which are found in
living cells. They are used to speed up specific reactions in the
cells. They are all very specific as each enzyme just performs one
particular reaction. They are known as biological catalysts
(substances which speed up reactions but which do not get used up

Enzymes help to turn the substrate into the product. The enzyme has an
active site that helps it to recognise its substrate in a very
specificway. Just like a key only fits into a specific lock, each
enzyme has its own specific substrate. This is called the lock and key

Of course all enzymes have a specific temperature that they work that
perfectly at, that makes them collide more frequently. If they get
hotter than this temperature, which is usually about 45°C (some have
certain microbes which can work at higher temperatures) the enzyme
dentures and stops working.

Catalase is an enzyme found in food such as potato and liver. It is
used for removing Hydrogen Peroxide from the cells. Catalase speeds up
the decomposition of Hydrogen Peroxide into water and oxygen. It is
able to speed up the decomposition of Hydrogen Peroxide because of the
shape of the Hydrogen Peroxide molecule. This type of reaction where a
molecule is broken down into smaller pieces is called an anabolic

A word equation for this is:


Hydrogen Peroxide èèèèèèèèWater and Oxygen

A diagram for enzyme activity:

Key Factors:

(Source: Biology Book)

In my experiment the key factors that could affect the results of my
experiment will be:

1. The temperature of the surroundings and test tubes

2. The pH value of its surroundings

3. The substrate volume

4. Mass of enzyme used

5. Surface area of active site - the one variable I am going to change
for my experiment

Of course, the rest of these factors will have to be kept the same to
keep the experiment a fair test. To do this, the experiment will take
place in the lab where the conditions are frequently the same and the
equipment should be kept the same to ensure all results are taken
without any advantages or disadvantages over any of the other
experiments. Everything in the experiment should be kept the same
apart from the surface area of the potato which will be cut by the
same scalpel and I will also try to cut it so they are basically the
same size.


To make sure that I am safe while carrying out the experiment, I must:

1. Wear safety goggles even before I start, as Hydrogen Peroxide is an
irritant that if gets in your eyes could be very harmful. Also if it
falls onto your skin it could cause a rash and persistent itching.

2. Putting all stools underneath the desk is vital as it could be
dangerous of it is lying around and somebody knocks into it.

3. Never sit down on the experiment, and don't take your eye off what
is happening.


I think that the enzyme will react greater with the potato and produce
more froth when it is cut up.

This is because as you cut it up into smaller bits, you make the
surface area greater meaning there are more enzymes to react with each
other, and there will be more successful collisions between the two

Preliminary work

Before we did the final experiment we did a run through to check that
we knew what we were doing. This gave us a rough estimate of what the
results would be, and see if our predictions were right. It also told
us how to conduct he experiment properly, and we worked out how we
were going to measure the froth, which was to measure just the froth,
and not the remaining liquid.

Our results for the preliminary work were:

Number of cuts made

Amount of froth produced (mm)

1st result

2nd result

No cuts



1 cut



Apparatus List:

Equipment Use

1 scalpel

To cut the potato into exact pieces (½, ¼ etc.)

Potato (10x1cm³)

Contains the enzymes to react with the hydrogen Peroxide

Hydrogen Peroxide (55ml³)


1 pair of Safety glasses

To protect your eyes from irritant chemicals

2 test tubes

To put the two reactants in

1 test tube rack

This is to store the test tubes in

1 Pipette

Dispense Hydrogen Peroxide into measuring cylinder

1 ruler

To measure the froth height

2 measuring cylinders

Measure accurately 5ml³ of hydrogen peroxide to pour into test tube

1 Stop watch

To time experiment (5 minutes)

1 Tile

To store the potato on and to cut it up on

1 pair of tweezers

Move the potato around without losing any of the enzymes

My Experiment


The first thing I will do will be to put on my safety glasses and push
stools under as this test needs to be made safe before anything can be
done. I will then get the equipment I need for the experiment, which
is listed above.

Once everything is set up, (i.e. test tubes in test tubes in racks) I
will, using a pipette, get 5ml³ of hydrogen peroxide and measure it
out accurately into a measuring cylinder. This will have to be done at
eye level so it is measured correctly. Do this into two separate
measuring cylinders. Now I will pick up a whole piece of a 1cm³ potato
with the tweezers and deposit it into the test tube. Once I have done
this into two test tubes, I will pour the hydrogen peroxide measured
out earlier into the test tubes and start the timer. This will now be
watched carefully for five minutes, without sitting down.

While this first experiment is underway I will get the potato cube and
cut it into halves, and again measure 5ml³ of hydrogen peroxide into
the measuring cylinders. Once the first experiment has finished, I
will take the measurement of the froth, from bottom to top. I will
only measure the froth though, and not the surrounding liquid. I will
then take this result down.

I will then repeat this method for ½, ¼, ⅛, and 1/16 of a 1cm³ piece
of potato. I will do this twice so my results are reliable, and then I
can tell if there are any anomalous results. I will then take an
average of these results.


Results in millimetres

Test Tube A

Test Tube B


Whole 1cm³ cube




1/2 of a cube




1/4 of a cube




1/8 of a cube




1/16 of a cube





(Sources: Science Book, Internet)

I think that the enzyme will react greater with the potato and produce
more froth when it is cut up.

This is because as you cut it up into smaller bits, you make the
surface area greater meaning there are more enzymes to react with each
other, and there will be more successful collisions between the two

This is my original prediction and I think it matches the results
quite well. As I made the surface area bigger, the reaction that took
place was quicker and produced more froth.

As I predicted, the more surface area that was on the active site, the
more froth would be produced (oxygen), which is a product of this
equation. This is shown in my results as there is a definitely a
pattern throughout the experiment that backs up my prediction.

This is because the molecules are always moving around normally anyway
and are fitting into the active site all the time. Of course this
reaction can be sped up by changing something. In our experiment we
changed the surface area, meaning that the substrate had more places
to work in because the potato was opened. Thus because of this, it
could produce the oxygen quicker and more often.


I thought that I followed my method well enough to produce some good
results. Even though, I think that I could easily improve my method.
Firstly, to improve the fair testing I could have done all the
experiments all at the same time as then they would have been subject
to the same conditions, and might not have some enzyme traces left in
the test tube when it is emptied out to use again. Also cutting up the
potato was a problem as it was not guaranteed to be the same shape all
the way through and cutting it into 1/16ths became very difficult to
get exactly right.

Another problem that I encountered was when I was taking the results,
with the ruler. I don't think was the most accurate way of taking the
results as there is a lot of room for human error with the shaking of
the hand. Also it was on the outside of the test tube which isn't very
accurate as it could be a different shape going up the test tube.

I repeated my results once for each type of cut, which vastly improved
the results because if their was an anomalous one, then it could be
corrected into an average even though this could create a problem as
it would drag the average down or up depending on the result. I'd say
most of our results were fine except for two obsolete figures that
where at the 1/8 cut. The results seem to slow down some what here,
and the last result to seem to have sloped off. I think that it should
be a straight line for my results and my average graph clearly shows

Overall, due to reliable repeats and in general predictions being
confirmed I feel my results are reliable enough to make a conclusion.

How to Cite this Page

MLA Citation:
"The Effect of Hydrogen Peroxide on Potatoes." 23 Apr 2014

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