Energetics of protein action Flashcards
How does pH affect vMax?
Vmax will vary with pH
When during enzyme catalysis is Gibbs free energy highest?
When the enzyme-substrate complex forms
What are hydrolyses?
Hydrolytic cleavages
What are polymerases?
Polymerisation reactions
What are synthases?
Synthesis
What are kinases and phosphatases?
Add phosphate
Remove phosphate
What are isomerases?
Rearrangements
What are oxido-reductases?
Oxidise substrate
Reduce substrate
What are ATPases?
Use ATP
What can an active site be divided into?
Residues that interact
Catalytic residues
What are the four things present in the different stages of a enzyme reaction?
Substrate + Enzyme
Substrate + Enzyme complex
Substrate + Product complex
Substrate + Produt
What is the name of the three processes in the progress of a reaction?
Binding
Catalysis
Release
What drives biochemical reactions?
Changes in free energy
What makes a reaction spontaneous?
Negative value of deltaG
How can we overcome the obstacle of non-spontaneous reactions?
Coupling exergonic and endergonic reactions
What factors affect catalysis?
Localisation of substrate
Orientation of substrate
Binding energy of substrate
Catalytic residues on protein framework
What is a transition state?
The state between substrate and products
How does the enzyme affect transition state?
The enzyme brings the substrate towards the transition state
What could be a source of activation energy?
Structural change
What determines the overall rate of the reaction?
The slowest step
What is Vmax?
The enzymes is fully occupied by the substrate
What does Vmax equal?
Kcat x [E]t
What is Km?
The substrate concentration where the reaction rate is half maximal
Michaelis constant
What is Vo?
Initial rate
How would you calculate enzyme efficiency?
Kcat/Km
How do you calculate Vo?
Vmax[S]/Km+[S]
What is the Michaelis Menten equation?
Vo=Vmax[S]/Km[S]
What is the Lineweaver Burk equation?
1/Vo=Km/Vmax[S] + 1/Vmax
What does a Lineweaver Burk plot show?
Plotting 1/Vo against 1/[S]
Where it crosses the X axis = -1/Km
Where it crosses the Y axis = 1/Vmax
What happens to Km and Vmax in competitive inhibition?
Km increases
Vmax unaltered
What happens to Km and Vmax in non-competitive inhibition?
Km unaltered
Vmax reduced
