Pepsin and Protein
Is the rate at which Pepsin digests protein affected by temperature?
I predict that it is affected by temperature. The optimum temperature
will be between 30°C and 40°C. This is because the average human body
temperature is 37°C. At 0-20°C (which includes the groups 0-10 and
10-20) the pepsin will not digest the protein for a long time. This is
because it is a too cold environment for the enzyme to work most
effectively and quickly. At 20-30°C the pepsin will work slightly more
quickly than at 0-20, but not as well as at 30-40, because it is
reaching the optimum temperature, though it is not quite there yet.
At the higher temperatures (i.e. 40-70°C) the enzymes will not work as
well. You may think that, using the pattern up to 30-40°C, the higher
the temperature, the quicker pepsin works. But this is not the case
because when it gets too hot, the enzymes start to lose their shape.
Enzymes use a very precise "lock and key" method to digest food. For
example pepsin, which is a protease enzyme, has a shape exclusive for
digesting protein molecules, and as soon as it changes its shape (in
this case due to heat) it cannot digest the molecule it was originally
designed to digest. Once it has changed shape it cannot change back
again. The "lock and key" is demonstrated below with diagrams.
The pepsin molecule locks onto the Glucose molecules are very
glucose molecule and breaks it complex but they still need
down into smaller particles. specially designed enzymes
that fit the molecules perfectly
to break them down.
If the temperature is too high and the enzyme changes shape, it can
never go back to its original shape. In the same way, if the enzyme is
at its optimum temperature, it does not change after the reaction, and
it can be used over and over again.
Another reason why I predict that temperature will affect the rate at
which pepsin digests protein, is because of preliminary experiments
that I have done. One was to investigate which temperature the enzyme
amylase digests starch molecules most quickly. We found out that it
was between 30-40°C that it worked the quickest. So, although pepsin
is a different sort of enzyme, designed to digest protein rather than
sugar, it ought also to work at that temperature.
We have also done another preliminary experiment in which we
investigated which environment (acid, alkali or neutral) pepsin worked
best in to digest egg white suspension (protein). We found that in the
alkaline and neutral environments, the enzyme was not able to work,
but in the acid, it did work. So we knew that we would have to use an
acid environment with the pepsin and protein, to make it as realistic
So, in short, below 30°C, the lower the temperature the slower pepsin