Lecture 13. Enzymes and Catalysis Flashcards
What does Eyring’s equation show ?
The rate of reaction can be related to Gibbs free energy of the transition state for that reaction
What is the activation state ?
The energy required to get to the transition state from starting materials
What happens as the activation energy increases ?
The rate constant (k) becomes smaller
The reaction becomes slower
What can catalysts do ?
- Reduce the activation energy for a reaction
2. Provide an alternative mechanism with a lower overall activation energy
Why are enzymes crucial for life ?
Activation energies for uncatalysed metabolic processes are so big that very high temperatures would be requires to achieve the same rates
What does a large difference in the activation energy result in ?
A larger difference in k catalysed and k uncatalysed
What can enzymes provide ?
A large reduction in the activation energy
What are the four categories by which enzymes catalyse reactions ?
- Proximity and orientation effects
- Acid base catalysis
- Covalent catalysis
- Transition state stabilisation
What type of cost does binding a substrate to an enzyme require ?
Entropic cost
What is required for a substrate to bind tightly to an enzyme ?
Favourable enthalpy
What does binding of substrate molecules to enzymes allow ?
The enzyme to exert control over the conformation and shape of the substrate molecule
What does free rotation around single bonds in acyclic systems result in ?
A huge number of thermally accessible conformations
Which type of reaction (intramolecular or intermolecular) are generally faster ?
Intramolecular
Why are intramolecular reactions generally faster ?
The reactants are already in the molecule
What can contribute to influencing the rate of acceleration ?
- Different functionality from different amino groups
- Shape and form of protein
- Interactions with the amide backbone