An experiment investigating the effects
heat has on the activity of enzymes reacting with a starch solution.
An enzyme is a
biological catalyst which increases the rate of chemical reactions without being
used up. Enzymes are also proteins made up of long chains of amino acids which
have optimum temperatures and pH values. This means that an enzyme will have
higher activity at the optimum and lower (with a possibility of becoming
denatured) if it is over heated, underheated or the pH level is too acidic.
Denaturing an enzyme leads to a change in the active site. This change makes it
harder to form bonds between an enzyme and a substrate, therefore an
enzyme-substrate complex can’t be made.
However, temperature can have a positive effect on an enzyme to a certain
degree. Heat increases kenetic energy between molecules which therefore
increases the rate of reaction between enzymes and substrates due to more
collisions being made.
graph shows how enzyme activity gradually increases until around 37ºC ( body
temperature), as the temperature continues to rise, the rate of reaction falls
due to the enzyme being denatured.
an enzyme that catalyses the hydrolysis of starch into smaller carbohydrates
and is made in the salvary glands and the
pancreas. Starch is a polysaccharide carbohydrate (C6H10O5)
consisting of large numbers of glucose monosaccharides joined together by
glycosidic bonds. When starch and amylase come into contact, the amylase
hydrolyses the starch causing it to be broken down into monomers of maltose
Hypothesis: Amylase will
take longer to breakdown starch molecules at higher temperatures as it becomes
denatured therefore it will take longer for the starch iodine solution to clear
as temperature increases.
Aim: To investigate the
effect temperature has on the activity of amylase hydrolysing starch in a
Planning: Equipment –
Large boiling tubes: to allow heat to be dispersed though the
solution to ensure solution isn’t heated for longer than is intended.
Chose to change the temperature the amylase was heated to due to amylase
being an enzyme and enzymes become denatured at around 40 degrees celcius. This
would limit the amount of enzyme activity as the active site would be altered
and an enzyme-substrate complex would not be made so the iodine would take
longer to clear.
Evaluation of pilot:
Overall, the pilot went well as the group worked together and got results that
were somewhat expected. Although the time taken for the solution to clear at 80
was a little faster than anticipated, the rest of the results were what were
Some confounding variables were that the iodine solution wasn’t dissolved
completely which left a lot of the powder in the solution even after adding the
amylase. This meant that the solution had to be shaken to ensure the colour
change was due to the reaction between the starch and the amylase and not
because of the iodine dissolving. Another confounding variable due to the
solution being shaken is that it was different people shaking it each time,
which could lead to a difference in how much the solution was disrupted and how
much of the colour change was down to the reaction and not how roughly the
solution was being mixed. The last confounding variable is that the waterbaths
didn’t maintain the set temperature. The temperature would drop rapidly which
would mean the amylase solution would lose heat quickly. This leads to
uncertainty to wheather or not the solution was up to the desired temperature
before it was added to the starch/iodine solution.
The group decided to change the experiment and see if heating both the amylase
and the starch/iodine solution would have an effect on how fast the solution
would take to clear. The reason for this was due to amylase and starch both
being the same temperature when reacting with oneanother in the body. It is
unusual to find amylase that is 80 degrees inside the body and starch which is
only 22 degrees.
The aim of this experiment was to investigate how heat effects the reaction
between amylase and starch. The hypothesis was that amylase heated above 40
degrees will take longer to break down starch molecules as enzymes become
denatured when heated too high. The results do not show support the hypothesis
as both the pilot and the main experiment have 80 degrees being either the
fastest or one of the faster times for the solution to clear. With this type of
experiment you would expect the solution to take longer to clear between 0 –
30, after this the enzyme activity would increase and the solution would clear
faster. Heating the amylase higher than 40 degrees would lead to the enzymes
being denatured and therefore the solution would take longer to clear.