Investigation on the Enzyme Trypsin
An Investigation determining a factor affecting the rate of digestion
of gelatin by the protease trypsin.
An enzyme is a biological catalyst, which speeds up reactions. An
example of this in the human body is trypsin (a protease produced in
the pancreas and used in the stomach), which catalyses the digestion
of gelatine, a protein. For this investigation, a photographic film
will be the source of the gelatine. I will be able to identify when
the gelatine is digested, when the photographic film turns from a dark
brown colour, to being transparent.
All enzymes are proteins, which are specific to the molecule that they
break down. This is known as the ‘lock and key’ theory, where the
active site only allows a specific substrate to be broken down,
eventually resulting in easier absorption (larger surface area).
Enzymes are made up of a long chain of amino acids, which form
together in such a way as to leave a specific pocket, into which a
substrate (as long as it fits perfectly into the pocket) can fit into
it like a key in a lock (hence the ‘lock and key’ theory). The
reaction then takes place, and the product of the substrate is then
released. The enzyme, not changed by the reaction, can then perform
the same “operation” on countless other substrates.
Because the enzyme can be re-used, only a small amount is needed.
Despite this enzymes can make cell reactions go many million times
faster than they would normally. Since enzymes are biological
catalysts, by definition, they are not used up or changed in the
reaction that they catalyse. Even though they cannot be used up, when
subjected to a high temperature (50°C and above), enzymes can become
denatured and the active site damaged or destroyed. After
denaturisation, the enzyme becomes useless as no more substrates can
become further digested by them.
Since there was ample trypsin for our use, and because trypsin begins
to denature by 50°C (the temperature of the water bath I was using), I
used a fresh batch of trypsin for each experiment I performed.
Before I started, it was important for me to decide what factor I was
going to set as my independent variable and what I was going to
setting as my dependant variable. There were several possibilities.
Since speeding up the reaction was obviously one option, I could have
changed either the heat of the reaction or the concentration of
trypsin. This is because heat results in molecules moving faster,
resulting in more particle collisions and a faster reaction (also each
collision is more likely to contain the activation energy required for
a successful reaction). Likewise, a higher concentration of trypsin
would result in more trypsin particles being involved in the reaction,
and there would be more chance of a successful...