Enzyme Kinetics Flashcards
What are the proportions of reactants and products when Kc > 1?
Products exceed reactants
- much greater than 1, reaction almost at completion
What are the proportions of reactants and products when Kc < 1?
Reactants exceed products
What factor affects Kc?
Temperature
What factors do not affect Kc?
- pressure
- catalyst
Zeroth law of thermodynamics
If 2 thermodynamic systems are in thermal equilibrium with a 3rd, then they’re in thermal equilibrium with each other.
First law of thermodynamics
Energy can’t be created/destroyed - can only be transferred.
Second law of thermodynamics
The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.
Third law of thermodynamics
As temperature approaches absolute zero, the entropy of a system approaches a constant minimum.
Define enthalpy ΔH
The change in heat associated with a chemical reaction.
What reactions take place when ΔH<0 or ΔH>0?
- Spontaneous exothermic reactions ΔH<0 (negative)
- Non-spontaneous endothermic reactions ΔH>0 (positive)
Define entropy ΔS
The degree of disorder
- Matter changes from a more ordered to a less ordered state.
(randomness in a system)
What reactions take place when ΔS<0 or ΔS>0?
- Spontaneous reaction ΔS>0 (positive)
- Not spontaneous reaction ΔS<0 (negative)
Gibbs Free Energy equation
ΔG° = -RTln(Kc)
What does the Gibbs Free Energy equation calculate?
Measures the difference in free energy between the products and reactants of a reaction.
- it is a thermodynamic property
(determines whether reaction is spontaneous or non-spontaneous)
What is the relationship between ΔG and standard-state to equilibrium?
- The smaller the value of ΔG, the closer the standard-state is to equilibrium.
- The larger the value of ΔG, the further the reaction has to go to reach equilibrium.
When do exergonic reactions occur?
- Spontaneously
- ΔG is negative
reactants E > products E
Draw an energy profile for an endergonic reaction
Slide 16 (part 1)
What factors affect reaction rate?
- temperature
- concentration
- addition of catalyst
- SA
Under what conditions can a reaction spontaneously occur?
- thermodynamically favourable
- kinetically favourable
What is the Collision Theory?
Reactions occur when molecules collide with:
- sufficient energy
- correct orientation
So bonds can be broken/made
How can the rate of a reaction be increased on a energy profile?
Increase number of successful collisions:
- change shape of curve
- move activation energy further to the left
What factors affect reaction rate explained by collision theory?
- increase in temp
- increase in conc of reactants
- addition of catalyst
How does the collision theory explain temperature as a factor?
Increase temp, rate of reaction increases.
- molecules move faster
- collide more often
- increase in number of high energy collisions
How does the collision theory explain concentration as a factor?
- higher concentration of reactants
- chances of collision are greater