Hypothesis Enzymes

Hypothesis Enzymes such as Catalase are large protein molecules that are found
in living cells. They are used to speed up specific reactions in the cells. They
are all specific as each enzyme just performs one particular reaction. In their
globular structure, one or more polypeptide chains twist and fold, bringing
together a small number of amino acids to form the active site, or the location
on the enzyme where the substrate binds and the reaction takes place. Enzyme and
substrate fail to join together if their shapes do not match exactly. This
ensures that the enzyme does not participate in the wrong reaction. The enzyme
itself is unaffected by the reaction. When the products have been released, the
enzyme is ready to bind with a new substrate. Enzymes work to change the rate of
a reaction without being absorbed by the reaction. The reactant that an enzyme
acts on is called the enzyme\'s substrate. The product is what the enzymes
convert the substrate into. Substrate + Enzyme = Product Catalase is an enzyme
found in food such as potato and liver. It is used for removing Hydrogen

Peroxide from the cells. Hydrogen Peroxide is the poisonous by-product of
metabolism. Catalase speeds up the decomposition of Hydrogen Peroxide (which is
the substrate) into water and oxygen as shown in the equations below: Hydrogen
peroxide + Catalase Water + Oxygen H2O2 + Catalase H2O + O2 It is able to speed
up the decomposition of Hydrogen Peroxide because the shape of its active site
matches the shape of the Hydrogen Peroxide molecule. This type of reaction where
a molecule is broken down into smaller pieces is called an anabolic reaction. In
this experiment Apparatus  Conical flask  Rubber bung 

Gas tube  Gas syringe  Measuring cylinders  H2O2
 H2O  Potato split into 4g tubes (enzyme catalase) 

Clamp stand  Cork borer  Glass rod  Thermometer 

2 decimal place balance  Pestle and Mortar  Sand  Beaker
 Scalpel  White tile  Safety goggles  Forceps
 Stopwatch The apparatus was set up as shown: A pilot test was carried
out to figure out how much and in what form the apparatus would need to be in.

This is what was concluded; the potato should be ground down with sand (which is
unreactive with H2O2) into a paste. This gives a larger surface area that
permits the reaction to go faster because the substrate molecules can get to the
enzyme molecules faster and more efficiently. The reaction will be timed as soon
as the solution (H2O2 and H2O) is added. The oxygen that evolves will be
measured and recorded every 30 seconds until the reaction finishes. The
concentration of the solution will be variegated in the experiment. This is the
only element that is varied everything else must stay the same to keep the
investigation unbiased. 25cm3 of solution was chosen to be used because in the
pilot experiment this was all that was necessary to produce a sufficient amount
of oxygen in the gas syringe so that it could be easily measured. If there were
more solution it would take longer to pour in to the conical flask therefore gas
would escape before the rubber bung could be fixed into place to seal the
conical flask. If less solution were to be used the reaction would take longer
because there wouldn’t be as many substrate molecules to react with the
enzymes. The solution will be measured in a measuring cylinder. The range was
selected because it is easily multiplied into 100, which is what is needed to
calculate percentages. The measuring cylinder was chosen to be used over all
other methods of measuring because it is easily available. Table to show H2O2 :

H2O Percentage of H2O2 Volume H2O2 (cm3) Volume of H2O(cm3) 100% 25 0 80% 20 5

60% 15 10 40% 10 15 20% 5 20 0% 0 25 The enzyme catalase works best at a warm
temperature so to speed the experiment up the conical flask will be in a water
bath at the temperature range 40-45 oC. The water bath needs to be kept at a
constant temperature because the enzymes will then be working at the same
constant rate. The mass of the potato needs to be kept the same at 4g so there
is the same amount of enzyme in each experiment. The overall amount of solution
needs to be kept constant to ensure that the % concentration is correct. The
oxygen evolved will be measured every 30 seconds from the