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1c) Control of Metabolic Pathways - Coggle Diagram
1c) Control of Metabolic Pathways
Enzyme action
Enzymes work by
induced fit
.
When an enzyme meets its substrate, it may not be an exact physical match.
Its shape may be slightly different to the active site.
As they start to bind, the active site moulds round the substrate until they fit
The substrate (having
high affinity
) joins to the enzyme at the active site
As it joins it changes the shape of the enzyme so the enzyme is able to catalyse the reaction
Conversely, enzymes have a
low affinity
for their product, meaning that once the product has been made, it is immediately released. This leaves the active site free for another reaction.
Summary
The substrate binds to the
active site
this changes the shape of the enzyme to better fit the substrate
(induced fit)
the reaction proceeds with less energy required
(lower activation energy)
so altering the substrate to become a product
which no longer binds (
low affinity
) and so is released
The enzyme turns into the
orginal shape
Factors Effecting Enzyme Activity
Suitable temperature
As the temperature increases the enzyme activity increases
The enzyme reaches a maximum rate = optimum
After the optimum the structure of the enzyme is denatured and the activity drops sharply.
Appropriate pH
Adequate supply of the substrate(s)
Whether or not an inhibitor is present
Graph
In slides/notes
Enzyme Inhibitors
Non-competitive
Do not bind to the active site
Causes a conformation change in the enzyme.
Causes a change in the active site - could be or not be permanent
May or not be reverable
Do not compete with substrate molecules due to not competiting with substrate molecules
Feedback
As the concentration of the end product drops
Fewer molecules of enzyme 1 are affected
and more of intermediate 1 is converted
into to intermediate 2 and so on
Called
negative feedback
Control and avoids the wasteful conversion and accumulation of intermediates.
Competive
A
similar shape
to the substrate molecule.
They fit into the
active site
Do not react
due to
different stucture
compared to substrate
Fewer substrate
molecules can
bind
to the enzymes so the
reaction rate is decreased.
Usally
temporary
and can be
reversed
by
increasing substrate concentration
Revsered by
Adding more substrate
increases the chance of the
substrate
molecule
colliding with the enzyme
and thereby
overcoming
competitive inhibition.