lecture 5 - enzymes Flashcards
Definition of a catalyst
A catalyst is a substance or material which accelerates a chemical reaction without being used up
How many different types of enzyme specificity are there?
- type of reaction
- positional specificity
- stereospecificity
What does Kcat stand for?
The rate constant for a catalysed reaction
Why do reactions with a negative delta G occur slowly or not at all?
The activation energy is too high. Energy input is needed to convert reactants into the unstable , transition state species
What is the equation for K
= Ae^(deltaGcat /RT)
4 way enzymes reduce activation energy
- hold substrates Close together in correct orientation
- provides a “microenvironment’
- puts strain on existing bonds
- sometimes is directly involved in the transition states
What is the most significant way in which the transition energy is reduced?
- multiple weak interactions are optimised in stabilising the transition state .
What are the 3 types of enzyme binding?
- lock and key
- induced fit
- transition state stabilisation
stereo - specificity
Enzymes can be highly specific in binding chiral substances . This is due to the fact that enzymes are also chiral
What Is geometric specificity?
Most enzymes are selective about the identities of the chemical groups on the substrates , but not all
What is the
induced fit hypothesis?
- The active site will interact with the substrate and adapt to it to make a perfect fit
What is the lock and ket hypothesis?
- complimentary binding
How do enzymes reduce the activation energies?
By multiple interactions stabilising the transition state. Enzymes have to show greater complimentary to the intermediate, not the substrate.
What happens if a reaction had a negative delta G?
Reverse reaction is less favoured
what does reducing the activation energy do?
increases the rate
