Lecture 9 - Introduction to enzymes Flashcards
Enzymes are
biological catalysts
Enzymes increase the
rate of a reaction
Enzymes speed up reactions, but cannot alter
the equilibrium constant or the free energy change
Enzymes lower the
free energy of activation
Activation energy is the
energy input required to initiate a reaction
The enzyme binds the
substrate
The substrate is the
molecule on which an enzyme acts
In an enzyme-catalyzed reaction, the substrate is a
reactant
In an enzyme-catalyzed reaction, the active site is the
portion of the enzyme surface to which the substrate binds
In enzyme-substrate binding, the first step is the
binding of substrate to the enzyme
In the lock-and-key model, the substrate binds to
the portion of the enzyme with a complementary shape
In the induced fit model, the binding of the substrate
induces a change in the conformation of the enzyme
_____ interactions dictate substrate-enzyme binding
non-covalent
The binding site is usually a ______ in the enzyme
cleft
Enzymes are highly specific in both
binding chiral substrates and catalyzing their reactions
The stereospecificity of enzyme binding arises from
the chirality of enzymes (L-amino acids)
Transition state analogs are compounds that can be used to
inhibit the activity of an enzyme
The functional groups of enzymes are inadequate at catalyzing
oxidation-reduction reactions
Enzymes that catalyze oxidation-reduction reactions utilize
cofactors
Cofactors can be
metal ions, organic molecules (coenzymes), prosthetic groups
Coenzymes are ______ by the enzymatic reaction
chemically changed
Coenzymes must be ______ to participate in further enzymatic reactions
returned to their original state
Many coenzymes are derived from
vitamins
Enzyme activity can be regulated by
- Control of enzyme availability
- Control of enzyme activity
Substrate binding affinity can be controlled by
small molecules (effectors)
Effectors can be
activators and inhibitors
ATCase is activated by _____ and inhibited by _____
ATP; CTP
CTP and ATP bind to the
regulatory subunits of ATCase
Feedback inhibition is a process by which the
final product of a series inhibits the first reaction in the series
Activators (ATP) preferentially bind to the
R state
Inhibitors (CTP) preferentially bind to the
T state
The T to R conformational change brings the two substrates
closer together in the active site
