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Chemistry Project Report on Chemical Reactions of Enzymes
Project Report on Chemical Reaction of Enzymes :
Chemical compounds undergo two types of changes. A physical change simply
refers to change in shape without breaking of bonds. This is physical process.
When bonds are broken and new bonds are formed, it is known as a chemical
Hydrolysis of starch into glucose is an organic chemical reaction as both
compounds are organic in nature
Rate of physical or chemical reaction refers to the amount of product formed
per unit time.
Rate can also be called velocity if the direction is specified. One of the
factor that influences the rate of physical or chemical processes, is
temperature. A general rule is that rate doubles or decreases by half for every
10 degree Celsius change in temperature in either direction. Reaction that
occurs in the presence of catalyst proceed at vastly higher rates or the
catalyzed reaction occurs very fast as compared to the unanalyzed ones.
In absence of the enzyme Carbonic anhydrate, this reaction is very slow
producing 200 molecule of H2CO3 in an hour. But when the
reaction occurs in the presence of this enzyme the reaction speeds dramatically
with about 600,000 molecules being formed every second. Thus the enzyme has
accelerated the reaction rate by 10 million times.
There are various types (thousands or type) of enzymes, each catalyse a
unique chemical or metabolic reaction. A multi-step chemical reaction , when
each of the step is catalyzed by the same enzyme complex or different enzymes,
is called metabolic pathway. For example glycolysis is a metabolic pathway in
which glucose is converted into pyruvic acid through ten different enzymes
catalyzed metabolic reactions.
This metabolic pathway with one or two additional reactions gives rise to a
variety of end products in different conditions.
In our skeletal muscles under anaerobic conditions the pyruvic acid is
converted into Acetyl CoA which in turn is converted into CO2 and H2O.In yeast
during the anaerobic conditions pyruvic acid is converted into alcohol by the
process of fermentation.
How do enzymes bring such high rates of chemical
In order to understand how enzymes bring such high rates of chemical
conversions, we need to study them a little more. We have already learnt about
the active sites. Now the chemical which is converted into a product is called
a substrate. Thus enzymes i.e., proteins with three dimensional structures
including an active site are capable of converting a substrate into a product.
The substrate S binds to the active site of the enzyme for which it has to
diffuse towards the active site. There is an obligatory formation of an ‘ES’
(enzyme substrate) complex. This complex formation lasts only for a short time
and is a transient phenomenon.
When substrate binds to the active site of the enzyme a new structure of
the substrate called transition state structure is formed.
The molecules of the substrate undergo chemical changes i.e.,
breaking/making of bonds finally the product is formed and is released from
the active site. Hence enzyme transformed the structure of the substrate into
The pathways of this transformation of substrate into product must go
through the so called transition state structure. There could be many more
altered structural states between the stable substrate and the product. In
this formation of substrate into the product, all other intermediate
structural states are unstable. Stability is something related to energy
status of the molecule or the structure.
For a reaction to start an external supply of energy is needed. It is
called activation energy.
Activation energy required for such a large number of reactions cannot be
provided by living systems. Enzymes lower the activation energy required for
In the given graph Y axis represents the potential energy content.
Potential energy of a body is its stored energy. The X axis represents the
progression of the structural transformation of substrate into product or
states through the transition state or we can say it represents the progress
If the energy level difference between s and p is such that P is lower
than S the reaction is ‘exothermic’. In exothermic reaction the energy content
of the product is lower than that of the substrate as heat is released.
External supply of energy is not required to form the product.
When S is at lower level than P reaction is Endothermic. In endothermic
reaction the energy content of the product is more than the substrate as the
reaction needs energy to proceed.
The difference in the energy level of the substrate and the transition
state is the activation energy required to start the reaction.
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