I was graded a distinction in all my applied science units, my assignments are extremely well written and contain all the information and pictures you need. If you have any questions do not hesitate to contact me :)I was graded a distinction in all my applied science units, my assignments are extre...
In this assignment I will be researching the effect of different factors on the activity of
enzymes. After carrying out research on the different factors I will conclude on which
factor I have chosen to further investigate.
What are enzymes and what do they do?
Enzymes are globular proteins that act as catalysts, as they “speed up reactions by
lowering activation energy” of the reaction, this speeds up the rate of reaction and
the enzyme itself is not consumed by the reaction. Enzymes are essential for
digestion, the muscles, and destroying toxins. Enzymes are reused, they aren't used
up in the reaction since they are not ractants. Once they have catalysed the reaction
with the substrate they can then be used for more reactions so therefore there
doesn't have to be an equal amount of substrates and enzymes. A common
misconception is that enzymes cause reactions to occur, however this is not true
(1),(9),(12) (21)
instead enzymes speed up the reactions which already occur.
In order for a reaction between a substrate and enzyme to occur:
1. they must collide with enough energy so their atom arrangement can be
changed and so they can then form the products.
2. The product's free energy has to be less than the substrate's free energy. For
example sucrose+water which are substrates, have to have higher free
energy than glucose and fructose which are the products.
3. In order for reactions to start they often require an initial amount of energy,
called the activation energy.
In order for the reaction to occur the activation energy has to be overcome. This
activation energy is lowered by enzymes, so enzymes can allow reactions to occur at
a lower temperature than what would normally be required. Since enzymes can do
this it allows some of the metabolic processes in the human body to occur rapidly at
temperatures of 37c which is the temperature of the human body. “In terms of
(1)
chemical reactions” this is a relatively low temperature.
1
,Ammara Aslam
p180267
(14)
Since enzymes are proteins they have a 3d shape which is specific, resulting from
the amino acid sequence. The amino acids within an enzyme molecule often carry a
charge. Positively charged and negatively charged amino acids will attract. This
contributes to the enzyme's shape and its active site. The active site is a region on
the enzyme which is functional. The active site forms a groove on the enzyme due to
the folding pattern of the protein. The active site is where the substrate molecule will
bind. When they bind they form an enzyme-substrate complex and there will be
temporary bonds which form between specific amino acids of the active site and
(3)(12)
groups on the substrate molecule.
The rate of reaction is “a measure of how quickly a reactant is used up, or a product
is formed.”. The rate of reaction can be calculated:
Rate of reaction= amount of substrate used or product formed/time taken. (6)
“Lock and key model of enzyme action”:
The lock and key model is an old, outdated model of enzyme action as it suggests
that the active site has a fixed shape and it doesn’t change shape, so it's therefore
complementary to one substrate. It proposes that enzyme action works the same as
a key and lock operate, the key has a specific shape and it only fits one lock. The
key in this instance is the substrate and the lock is the enzyme. After a successful
collision between the enzyme and substrate, they form an enzyme-substrate
complex which leads to a reaction which gives the products from the substrate. (22)
The induced fit model is a much more accurate representation of enzyme action as it
suggests the active site slightly alters its shape, so enzymes do not have a rigid
structure which the lock and key model suggests but they are slightly flexible.
2
,Ammara Aslam
p180267
(10)
“Induced fit model of enzyme action”:
The induced fit model is a scientific model to represent how enzymes work. The
recent and accepted model of enzyme action is the induced fit model which suggests
that before a reaction an enzyme's active site is not complementary to the substrate
and it doesn't fit the substrate, when the enzyme and substrate collide the active site
changes shape to fit the substrate as the substrate binds and an enzyme substrate
complex forms. So the enzyme is flexible and it can change its shape in order to fit
the substrate. Enzymes do have a specific shape however in the presence of a
substrate they alter. This stresses and distorts bonds in the substrate leading to a
(2), (23)
reaction producing the products.
(11)
Factors affecting enzyme action
The Factors which affect the rate of enzyme activity are:
1. Substrate concentration
3
, Ammara Aslam
p180267
2. Temperature
3. pH
In order for an enzyme to carry out its function it must physically
1. come into contact with a substrate
2. the substrate must fit the enzyme's active site.
The factors influencing enzyme activity do so by affecting either one of the two
above. (1)
Measuring enzyme catalysed reactions
An enzyme catalysed reaction progress can be measured by measuring its time
course. The changes which are most often measured are:
1. The substrate disappearance, for example amylase works on starch and the
reduction of starch would be measured.
A graph for this would look like:
(1)
2. The reactions formation of products, for example the enzyme catalase acts on
hydrogen peroxide and it forms oxygen so oxygen would be measured. A
graph for this factor would look like:
4
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