WK 5 (Enzymes) Flashcards
True or False
Co-ordination of metabolism is largely due to regulation of enzyme activity
True
Enzymes facilitate increased rate of chemical reactions by…
Decreasing the activation energy required for the reaction to progress
Why are atoms in constant vibration, rotation and motion?
Thermal motion, heat energy is constantly being liberated by chemical reactions
How do enzymes lower the activation energy of a reaction?
Binding of the enzyme alters the shape or chemical characteristics of the substrate molecule
Binding site of an enzyme is also referred to as
the active site
How do enzymes work?
1) binding of the substrate/s to the enzyme to form an enzyme-substrate complex.
2) progression of the chemical reaction facilitated by a lowered activation energy.
3) formation of an enzyme-product complex.
4) dissociation of the product/s from the enzyme (leaving the enzyme to catalyse the reaction of another substrate molecule.
Protein Kinase
Addition of a phosphate group to a protein
Protein phosphatase
Removal of a phosphate group from a protein
Enzyme catalysis:
a) increases the rate of chemical reactions by decreasing the activation energy required by a molecule to enter a reaction
b) decreases the rate of chemical reactions by decreasing the activation energy required by a molecule to enter a reaction
c) Increases the rate of chemical reactions by increasing the activation energy required by a molecule to enter a reaction
d) Decreases the rate of chemical reactions by increasing the activation energy required by a molecule to enter a reaction
a)
Enzyme Kinetics
The factors that affect or regulate enzyme activity
Factors rate of reaction (enzymes bind at random due to thermal motion)
- The concentration of the substrate is important
- The speed of the progression of the chemical reaction
- Affinity of binding between substrate and enzyme is important
4, How quickly an enzyme dissociates with its products
Vmax
Maximum rate of enzyme activity (all enzyme molecules are fully occupied with substrate)
Km
Concentration of substrate at 1/2 maximal rate
The Michaelis-Menton equation describes:
a) the relationship between rate of enzyme catalyzed chemical reactions and substrate concentration
b) the specificity of an enzyme in binding with its substrate
c) the affinity of an enzyme to its substrate
d) the way in which enzymes can be used in clinical diagnosis
a)
Feedback
Enzyme (regulatory enzyme) early in a pathway is regulated by a product liberated from late in the pathway
E.g. will bind to the enzyme at the active site (competitive) or at a regulatory site (non-competitive) and affect:
- Availability of active site
- The shape of the enzyme
- Chemical characteristics of the enzyme
Allosteric enzyme
Enzyme adopts 2 or more slightly different conformations depending upon ligand stabilisation and this affecting activity
Is feedback inhibition (non-competitive) reversible?
Yes
i.e. the inhibitor/stimulator ligand will dissociate from the enzyme
Is the action of inhibitors of enzyme function always reversible?
No, in some causes it is irreversible
