Describe the structural features of an enzyme (P4)
Enzymes are proteins which are specialised to carry out a specific role. They are globular
proteins due to their usually spherical shape which is a direct consequence of the tight folding
of their polypeptide chains. They have an active site which is specific to each enzyme
depending on its role within the body and is provided by a very specific tertiary or quaternary
structure. It is where the substrate binds to the enzyme.
Enzymes also have various side chains that aid in stabilising the structure, for example one of
the amino acid side chains is an amino group, containing nitrogen. There is a carboxyl group
and an R group which can also aid in stabilising the structure. The tertiary and quaternary
structure is supported by the amino acid side chains, this is what results in the creation of the
active site as the R group is variable and as a result changes depending on the amino acid
involved. The side chains as a result hold the specific tertiary structure of a polypeptide chain
together and hold hydrogen bonds between each of the polypeptide chains.
Enzymes are also generally larger than the substrate they act on with the active site,
consisting of about 3 to 12 amino acids is the only part that comes into direct contact with the
substrate to form an enzyme-substrate complex. The majority of the amino acids of the
enzyme function to maintain the correct tertiary shape which is important for the active site to
function at the maximum rate achievable.
They act as biological catalysts since they are produced by living cells, while also allowing
reactions to occur at the same speed as reactions outside of the body but at a lower
temperature.
They are also soluble resulting in having specific roles in metabolisation, which can involve
catabolic reactions such as breaking down food molecules or anabolic reactions involving the
synthesis of larger molecules from smaller ones. In an anabolic reaction, the substrate
molecules are orientated on the active site so as to allow bonding to occur between them,
whereas in a catabolic reaction, the way the active site forms around the substrate, helps to
break particular bonds to split it to form an enzyme-product complex.
There are two main types of enzymes; they can be intracellular which means that they are
used inside cells and control the metabolism, or they can be extracellular and are produced
inside of cells however they are excreted by exocytosis and work outside of the cell, for
example as a digestive enzyme.
Without enzymes, reactions would occur far too slowly to maintain life. Some metals are also
able to catalyse reactions however as they are not as specific, they work at a much slower rate
than enzymes.
In order for chemical reactions to happen between particles that collide, there must be
sufficient energy available and this is called the activation energy. It is needed to break
existing bonds inside molecules. Enzymes lower the activation energy required by providing
a different pathway for the reaction to follow.
This leads onto two different hypotheses of the mechanism of enzyme action:
The lock and key hypothesis and the induced fit hypothesis.
Enzymes are proteins which are specialised to carry out a specific role. They are globular
proteins due to their usually spherical shape which is a direct consequence of the tight folding
of their polypeptide chains. They have an active site which is specific to each enzyme
depending on its role within the body and is provided by a very specific tertiary or quaternary
structure. It is where the substrate binds to the enzyme.
Enzymes also have various side chains that aid in stabilising the structure, for example one of
the amino acid side chains is an amino group, containing nitrogen. There is a carboxyl group
and an R group which can also aid in stabilising the structure. The tertiary and quaternary
structure is supported by the amino acid side chains, this is what results in the creation of the
active site as the R group is variable and as a result changes depending on the amino acid
involved. The side chains as a result hold the specific tertiary structure of a polypeptide chain
together and hold hydrogen bonds between each of the polypeptide chains.
Enzymes are also generally larger than the substrate they act on with the active site,
consisting of about 3 to 12 amino acids is the only part that comes into direct contact with the
substrate to form an enzyme-substrate complex. The majority of the amino acids of the
enzyme function to maintain the correct tertiary shape which is important for the active site to
function at the maximum rate achievable.
They act as biological catalysts since they are produced by living cells, while also allowing
reactions to occur at the same speed as reactions outside of the body but at a lower
temperature.
They are also soluble resulting in having specific roles in metabolisation, which can involve
catabolic reactions such as breaking down food molecules or anabolic reactions involving the
synthesis of larger molecules from smaller ones. In an anabolic reaction, the substrate
molecules are orientated on the active site so as to allow bonding to occur between them,
whereas in a catabolic reaction, the way the active site forms around the substrate, helps to
break particular bonds to split it to form an enzyme-product complex.
There are two main types of enzymes; they can be intracellular which means that they are
used inside cells and control the metabolism, or they can be extracellular and are produced
inside of cells however they are excreted by exocytosis and work outside of the cell, for
example as a digestive enzyme.
Without enzymes, reactions would occur far too slowly to maintain life. Some metals are also
able to catalyse reactions however as they are not as specific, they work at a much slower rate
than enzymes.
In order for chemical reactions to happen between particles that collide, there must be
sufficient energy available and this is called the activation energy. It is needed to break
existing bonds inside molecules. Enzymes lower the activation energy required by providing
a different pathway for the reaction to follow.
This leads onto two different hypotheses of the mechanism of enzyme action:
The lock and key hypothesis and the induced fit hypothesis.
