Catalysis Mechanisms Flashcards
Cage Effect
Orientation of two or more substrates to Enzymes
Strain Effect
External strain is expressed on the enzyme in order to help the reactions along
Covalent Mechanism
Substrate gets covalently bonded to the enzyme
Acid-Base Mechanism
Characterized by the transfer of Protons
Metal Ion
A metal ion is used in order to promote proper orientation of bound substrates and may aid in redox reactions
Give an example of the Strain mechanism
A lysozyme uses strain to enhance breakage in bacterial cell walls. Lysozymes are found in saliva to destroy bacteria. The active site deforms the substrate (strain) in order to cleave the bond
Give an example of the Cage Effect mechanism
Citrate synthase–Two substrates are bound in the correct orientation for reaction
Give an example of the Acid-Base mechanism
Chymotrypsin is a gut enzyme that breaks down proteins and peptides. Has a covalent intermediate.
Give an example of the Covalent mechanism
Glyeraldehyde-3-Phosphate dehydrogenase
Give an example of the metal ion mechanism
Carbonic anhydrase uses Zn2+
How do you recognize the cage effect mechanism?
Multiple Substrates (at least 2)
How do you recognize the strain effect mechanism?
Physical strain on the substrate
How do you recognize the Acid-Base mechanism?
A proton is being transfered
How do you recognize the metal ion mechanim?
A metallic ion like Zn is actively participating in the reaction
How do you recognize the covalent mechanism?
Covalent bond formed between the enzyme and the substrate
How do enzymes increase reaction rates?
- Reduce the transition state energy
- Provide an alternate path for product formation
- Reduce entropy by binding and orientating multiple substrates
What are cofactors?
Non-Protein compounds required for activity
What are coenzymes?
Ligands - Non-protein compounds required for activity
Should the change in Gibbs free energy be negative or positive for a spontaneous reaction?
NEGATIVE
What energy conditions are favorable for reactions?
Reactions are favorable when the free energy of the products is lower than the reactants–NEGATIVE FREE ENERGY
What is Energy of Activation (EA)?
A barrier to direct conversion of substrates to products
How does the addition of an enzyme affect the energy of activation?
It lowers it considerably
How does the addition of an enzyme affect the change in Gibbs free energy?
It doesn’t affect it at all. There is no change
How does the enzyme lower the activation energy?
It stabilizes the transition state
