Enzyme Kinetics Flashcards
What are enzymes ?
- enzymes are biological catalysts
- they work under mild conditions
- they are specific for a particular reaction and a particular substrate
- they can be regulated to control the speed of reactions
What do enzymes do ?
1) they bind 2 substrate molecules and orientate them to lower the activation energy
2) they bind a substrate and rearrange the electrons to lower the activation energy
3) they place a strain on the bonds in the substrate to lower the activation energy
What is enzyme kinetics ?
The study of how the rate of the catalysed reaction changes when the experimental conditions are changed
Briefly describe what happens when a substrate binds to an enzyme
The substrate binds to the enzyme and this is a reversible process
The reaction then occurs and the products dissociate
E + S <> ES > E + P
How does substrate concentration affect enzyme activity ?
At low substrate concentration, only a small amount of enzyme substrate complexes form
As substrate concentration increases the number of enzyme substrate complexes formed increases
At high substrate concentration most of the enzymes have a substrate bound and so the enzyme is now limiting the rate of the reaction and the rate of the reaction will remain the same
What is V max ?
It is the maximum velocity of the enzyme
What is the name given to the equation used to calculate the velocity of an enzyme ?
The Michaelis - Menten equation
What are the 2 isoenzymes of hexokinase ?
- hexokinase (found in all cells)
- glucokinase (found in liver and pancreatic beta cells)
They both catalyse the same reaction but have different kinetics
What has enzyme inhibition been useful for ?
It has been useful in -
• understanding how enzymes work
• producing drugs
What are the 2 types of reversible inhibition ?
- competitive inhibition
- non competitive inhibition
How does competitive inhibition work ?
The inhibitor has a similar tertiary structure to the substrate and so it binds to the enzyme active site
This means the substrate and inhibitor cannot be active at the same time
How does non-competitive inhibition work ?
The inhibitor binds to the allosteric site and changes the tertiary structure of the enzyme active site so the substrate is no longer able to bind to the active site
What is irreversible inhibition ?
It is when an inhibitor binds to an enzyme permanently
What can irreversible inhibitors be used for ?
In the diagnosis and treatment of disease
