Lecture 4: Enzymes Flashcards
What is Keq?
[AB]/[A][B]
Characteristics of negative ΔG
- Spontaneous
- Energy is released
- Products have a less free energy (G) than reactants
- Thermodynamically favorable
- Exothermic
Characteristics of positive ΔG
- Non-Spontaneous
- Energy is inputted
- Products have a more free energy (G) than reactants
- Thermodynamically unfavorable
- Endothermic
If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?
The reaction will stay at equilibrium.
What influences whether a reaction will proceed?
- Concentration of reactants
If low conc. of reactants, equilibrium shifts to the left and rxn won’t proceed.
If high conc. of reactants, equilibrium shifts to the right and rxn will proceed.
- Concentration of products
If high conc. of products, equilibrium shifts to the left and the rxn won’t proceed.
If lwo conc. of products, equilibrium shifts to the right and the rxn will proceed.
- Environmental conditions: Temp, pH, Salt conc.
What do enzymes not change?
ΔG
Describe the transition state.
Highest energy point of the rxn
Thermodynamically unfavorable
Unstable
If reactants can reach the transition state, they can spontaneously form products.
How do enzymes lower Ea of rxns?
- Create high local conc. of substrates
- Hold the substrate in precise orientation that facilitates bonding
- Allow substrates to persist in the transition state, increasing the probability they will react and form products
What is the Induced Fit model?
The enzyme changes shape slightly when the substrate binds.
What are the differences between competitive and noncompetitive inhibitors?
Competitive inhibitors bind to the enzymes active site, but with enough substrates, the substrates can out compete the competitive inhibitors. With enough substrates bound to the active site, the reaction can proceed.
Non competitive inhibitors bind to the allosteric site not the active site and inhibit the enzyme, so the rxn is inhibited.
What is Q10?
How much the rate of [AB] formation changes when the temperature is increased by 10 degrees celsius?
How might feedback inhibition adaptive? How is positive simulation adaptive?
Feedback inhibition: Enables a rxn when it is beneficial and prevents it when it isn’t
Positive simulation: Enables a rxn when it is beneficial
How does coupling rxn make a rxn with a positive ΔG go?
Couple a rxn with a higher negative ΔG to a rxn with a positive ΔG. The spontaneous coupled rxn will have a negative ΔG for both rxns.
Why are enzymes often in complexes?
Allows for reaction intermediates to be passed between enzymes sequentially
