Enzymes Flashcards
What are the 2 models that create enzyme substrate complexes
Lock and key
Induced fit
Describe the lock and key model
Each enzyme has a specific active site which only one specific substrate will bind to
This forms a enzyme substrate complex
What is the limitation of the lock and key theory
It suggests the enzyme has a rigid structure, however it has been observed that molecules can bind and alter the shape of the enzyme
Describe the induced fit model
Proposes that the enzyme can slightly change its shape, it can be flexible and mould to fit the substrate - this is called a conformational change
What is a conformational change
A change of shape
What happens in the induced model once the enzyme has changed shape? What does this do?
It puts a strain on the substrate, this strain distorts a particular bond and lowers the activation energy needed to break the bond
What does an inhibitor do to enzymes
Stops them from working
What are the two types of inhibitors
Competitive and non competitive
What is a competitive inhibitor
An inhibitor which binds directly to the active site to stop and substrate from getting in preventing the enzyme from working
What is a non competitive inhibitor
Binds to an allosteric site which will change the shape of the active site so the substrate can no longer bond
What is an allosteric site
A place on the enzyme that isn’t the active site
How do enzymes act as biological catalysts
Each enzyme lowers the activation energy of the reaction is catalyses to speed up the rate of reaction
Describe the induced fit model step by step
- Substrate binds to (not completely complementary) active site of enzyme
- Causing the active site to slightly change shape and mould so it is complementary to its substrate
- Enzyme substrate complex forms
- This causes the bonds in the substrate to bend or distort lowering the activation energy
Explain the specificity of enzymes
The specific tertiary structure determines the shape of the active site - this is dependant on the primary structure of the amino acid sequence
The active site is complementary to a specific substrate, which can only bind to an active site, inducing fit and forming an enzyme substrate complex
