Unit 1 - Chapter 2 Role of Enzymes Flashcards
Enzymes are biological
catalysts
Catalysts speed up chemical reactions without being
affected themselves
When enzymes build up large molecules it is called a
synthesis reaction
When enzymes break down large molecules it is called a
degradation reaction
An active site of an enzyme is specific to only one
substrate
Enzymes are made of protein so are affected by
temperature and pH
At a low temperature there are few collisions between
substrate and enzymes so the reaction is low
As temperature increases so does
the rate of reaction
The reaction rate reaches its maximum when the temperature reaches
optimum
At a temperature past optimum the enzyme protein begins to
denature
Enzymes are active within a narrow ph
range
Most enzymes have an optimum pH which is
neutral or slightly alkaline
The exception to the optimum pH is pepsin which has an optimum of
pH 2
Enzymes control biochemical pathways both
inside and outside the cell
Essential metabolic pathways can be stopped if a mutation
codes for an ‘enzyme’ of the wrong shape
PKU is an example of a
inherited disorder
PKU is when an essential metabolic pathway is
prevented by the absence of an enzyme
The activity of an enzymes increases as the substrate
concentration increases
Substrate concentration gives a reaction rate increase until
all the active sites are working at their maximum rate
The rate of reaction increases as the enzyme concentration increases as
there are more active sites for substrate molecules.
A competitive enzyme inhibitor has a similar shape to the
substrate and so competes for the active site of the enzyme
As the proportion of competitive inhibitor to substrate increase the
rate of reaction decreases
A non competitive enzyme inhibitor binds to the enzyme permanently and changes the shape of the
active site which prevents substrate molecules from binding.
A non competitive inhibitor produces
non functional enzymes
Non-competitive inhibitors reduce the rate of reaction whatever the
substrate concentration
An example of non-competitive inhibition is
lead
Lead is a non-competitive inhibitor which
slows down the reaction rate of the enzyme catalase
Many enzymes depend on co-factors such as
mineral ions or vitamins
Digestive enzymes for example Trypsin are converted from
inactive to active state by another enzyme
Vitamins are used to make co-enzyme molecules essential for
the activity of some enzymes e.g. the hydrogen acceptor NAD
A variety of mineral ions are essential cofactors to activate
a number of enzymes e.g. iron in catalase
