Research molecular oxygen and water. (Student sheet 24).

Research Question: What effects does different concentrations
of hydrogen peroxide (0%,5%,10%,15%,20%,25%,30%) have on time taken for 20cm3 of
oxygen to be made?



Background Information:

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are proteins that function as catalysts for chemical reactions that occur in
living cells. An individual enzyme can only accelerate the reaction of only one
chemical reaction (Mäntsälä et al.). Nonetheless, this does not limit their
ability speed up the reactions in cells. An example by Mäntsälä et al. which
was related to the investigation stated that “In the presence of catalase, the
decomposition of H2O2 occurs 108 times faster than in the absence of catalase”.


is a common enzyme found in nearly all aerobic cells. It accelerates the
decomposition of hydrogen peroxide into water and oxygen (Chelikani, P., et al).

Catalase is extremely important in cells because it prevents the accumulation
of hydrogen peroxide produced as a by-product of cell metabolism. Because hydrogen
peroxide is a strong oxidizing agent, it disrupts the cell chemistry (Nindl et
al.) and it will kill the cell so catalase quickly neutralizes it before damage
is done. It does this by catalyzing the decomposition of hydrogen peroxide into
molecular oxygen and water. (Student sheet 24). The chemical equation for this
reaction being:


2 H2O2 ———–> 2 H2O + O2


also significantly important because catalase has one of the highest turnover
numbers of all enzymes which essentially means that one catalase molecule can
convert millions of molecules of hydrogen peroxide to water and oxygen each
second. Thus, catalase is most effective at degrading high concentrations
of hydrogen peroxide (J.P. Kehrer et al.)


of catalase similar to other enzyme reactions can be manipulated by a variety
of factors such as pH levels, temperature, inhibitors… This experiment is
designed to focus purely on the effect of substrate concentration on the rate
of catalase reaction.



this assessment, the rate of catalase reaction by substrate concentration will
be explored. This is achieved by having the catalase react to varying degrees
of hydrogen peroxide concentration (0%,5%,10%,15%,20%,25%,30%) and timing how
long it takes to produce 20cm3 of oxygen. Being a student who didn’t do the
IGCSE and DP1 of IB Biology, I have certainly missed out a lot on what I consider
as biology basics. This investigation does not only serve as a way for me to
connect with old concepts but also allow me to look at one of the things I was
amazed at Biology. In my first few encounters with the subject, what amazed me
was the revelations that millions of tiny interactions that takes place beyond
normal vision. If catalase can convert millions of molecules, I want to ‘see’
this process of enzyme reactions in real time.



on background information, it will highly be that as the concentration of
hydrogen peroxide increases, the time taken for 20cm3 of oxygen to form will decreases.

So inversely the rate of reaction between the catalase and hydrogen peroxide
will increases.

Due to the fact that as
substrate concentration increases, more enzyme-substrate complexes will be
formed and as a result there will be fewer hydrogen peroxide molecules that are
free, thus causing the rate of reaction to increase at a slower rate and
eventually plateau.


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