TA: Minghui Zeng
18 March 2007
LABORATORY REPORT – ENZYMES
Chemical reactions such as hydrolysis and dehydration synthesis can be controlled by adjusting
the points where catalysis takes place.
Catalysts are protein-like, although recent studies have
shown that some types of catalysis occur due to ribonucleic acid (RNA) molecules.
basically control earth’s living organisms.
Enzymes are biochemicals that are responsible for
carrying out the catalysis that occurs in all organisms.
The three-dimensional shape of an enzyme allows it to maintain an association between
substrates, molecules that will undergo a certain reaction, for a temporary amount of time.
reaction has large amounts of activation energies, the reaction is very slow.
are capable of lowering activation energies, thus increasing the reaction rate.
In this chemical
reaction, the enzymes remain unaltered physically, and therefore, only a small amount of enzyme
Enzymes can be reused over and over again.
Reaction rates can also be increased by
physically, instead of chemically.
Increasing the temperature causes molecules to move faster
and have a bigger chance for molecular collisions.
The reaction rate depends on the
concentrations of the substrate and enzyme.
Physical and chemical disturbances, that change the
enzyme’s three-dimensional shape, ultimately determine if the enzyme is able to catalyze a
Increases in temperature cause the reaction rate to also increase, because increases in heat
temperature cause random molecular movement. But if the temperature reaches higher than the
optimum, the reaction rate will be slow and therefore, the enzyme denatures.
Also, the pH levels
of vinegar (pH 3) or pepsin (pH 2) are very extreme and are higher than the optimum pH (6 to 8),
and in turn, also denature the enzyme.
The substrate amount also can alter the reaction rate: more substrate equals faster reaction rate.
But this is true only up to a certain point.
Once all the substrate molecules are coupled up with
the enzyme molecules, the reaction rate cannot increase any more because it is already at its
And the leftover, uncoupled substrate molecules do not cause the reaction rate to
If a graph was drawn of this situation, you would see a point on the graph where the
line levels off to look like a plateau, where the enzymes are saturated.
The enzyme activity will be examined by using live yeast cells.
Living yeast cells are the
provider of sucrase, an enzyme that breaks disaccharide sucrose down to a molecule of glucose
Since sucrose is too large of a molecule to enter into most cells, the yeast will
produce sucrase, which hydrolyzes sucrose into smaller monosaccharides that are then able to
enter the cell.