Lecture 5 - Enzymes and Catalysts Flashcards
What are Enzymes
Biological catalysts that speed up specific enzyme reactions
What causes enzymes to lose their catalytic activity
if the enzyme is denatured (dissociated from its subunits)
What is enzyme specificity?
The ability of the enzyme to specifically recognise the proper substrate (reactant)
Where do substrates bind to
Active Sites
What are the 2 models of substrate active site binding
- lock and key
- induced fit
What is the lock and key system
When the active site and substrate are a perfect fit for each other
What is induced fit
When the substrate isn’t a perfect fit to the active site resulting in a conformational change allowing a better fit.
What is the active site composed of
- Substrate Binding Site
- Catalytic Site
What is the substrate binding site composed of
Amino acid side chains interact with the substrate through hydrogen bonding and other electrostatic interactions
What is the activation energy?
The minimum amount of energy required to start a reaction
How do enzymes achieve catalysis?
By reducing the activation energy of the transition state
Why do proteins lose activity at high temperatures?
Denaturation occurs - loss of native folding
What is the pH of enzymes in the intestine?
7.5
What is the pH of stomach enzymes
1.5
What is the pH for lysosomal enzymes?
4-5
What is a steady state?
When vMax is reached
What is KM
The concentration of substrate at which the reaction rate is half-maximal
What are enzyme inhibitors?
Molecules that interact with enzymes which can cause temporary or permanent block in enzyme activity
What are the 2 types of enzyme inhibitors?
- Competitive
- NonCompetitive
What are enzyme cofactors?
- essential ions
- Coenzymes (organic molecules)
What are essential ions composed of
- Activator ions
- Metal ions for metalloenzymes
What are Coenzymes made of
- Cosubstrates
- Prosthetic Groups
What is a Holoenzyme
A completely catalytically active enzyme together with its cofactor
What is a Holoenzyme
A completely catalytically active enzyme together with its cofactor
What is an apoenzyme
The protein part of the enzyme without its cofactor
What are the 7 Classes of enzymes
oxidoreducatases
transferases
hydrolases
lyases
isomerases
ligases
translocases
