Enzyme Flashcards
What are enzymes?
class of proteins that speed up reactions
Why do all modern life forms require
enzymes?
Most chemical reactions are very slow.
how do enzymes work?
Enzymes bring substrates (reactants) together
- In specific positions that facilitate reactions
Substrates bind to the enzyme’s active site
Interactions between the enzyme and the substrate
– Stabilize the transition state
– Lower the activation energy required for the reaction
to proceed
The transition state
the fleeting molecular
configuration when old
chemical bonds are breaking
and new once are building
The activation energy (Ea) of a reaction
is the amount of free energy required to reach the
intermediate condition, or transition state.
are enzymes catalysts?
yes
The speed of an enzyme-catalyzed reaction
- Increases linearly at low substrate concentrations
- Slows as substrate concentration increases
- Reaches maximum speed at high substrate
concentrations
can enzymes be saturated?
yes
The rate of a reaction is limited by the amounts of
– Substrates present
– Enzyme available
What Limits the Rate of Catalysis?
Active sites cannot accept substrates any faster no
matter how large the concentration of substrates gets
what effects the enzymes shape and reactivity?
temp and pH
The rate of an enzyme-catalyzed reaction depends
on:
– Substrate concentration
– Enzyme concentration
– Temperature
– pH
– The enzyme’s intrinsic affinity for the substrate
– enzyme regulation (competitive inhibition, allosteric
regulation, enzyme phosphorylation)
Allosteric regulation
the regulatory molecules does not bind to the
active site.
The function of an enzyme can be altered by
a chemical change in its primary structure
Most common modification of enzymes is
– The addition of one or more phosphate groups (PO43-)
– To Ser, Thr, Tyr, and His
Phosphorylation of an enzyme is
A reversible modification to the protein’s structure
