Biochemistry Basics Flashcards
Overview of specific concepts / core info
Relationship b/w spontaneous/nonspontaneous reactions and entropy/energy
- *Spontaneous reactions**
- occurs without outside intervention
- increase disorder of the universe
- ΔG = negative
- *Nonspontaneous reactions**
- a process that requires input of energy to occur
- cannot be made spontaneous through the use of a catlayst
- ΔG = positive
Determining total energy change for a system under any given set of conditions
ΔG = change in free energy for a system
ΔG = ΔH - TΔS
units: kJ mol-1
Enthalpy
a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.
ΔH = ΔE + PΔV
ΔH= change in enthalpy ΔE= change in bond energy of products and reactions ΔV= change in volume P= pressure
postive/negative gibbs and enthalpy
ΔG positive = nonspontaneous; endergonic
Δ G negative= spontaneous; exergonic
ΔH positive = exothermic (heat given off)
ΔH negative = endothermic (heat absorbed)
A system will always move in direction of the ___
lowest free energy
negative ΔG means that a goes to a lower __
free energy state
ΔGo’ and the equiibirum constant
ΔGo’ = -RTlnK’eq
R = gas constant (given on MCAT, pay attention to units)
T = Temperature (K)
K’eq = ratio of products to reactions at equilibirum
Keq = [Products]y
[Reactants]x
Calculating change in free energy under physiological conditions
ΔG = ΔGo’ + RT lnQ
relationship between Q and Keq
Q is the ratio of products to reactions in any given set-up. Keq is ratio at equilibirum. When we disturb an equilbiirum mixture, this causes a change in Q but not in Keq, and the reaction will proceed in the direction necessary to re-establish equilbrium.
Does Q or Keq descrive the properties of the reaction.
The size of Q says nothing about the properties of the reactants and products. Q is calculated from whatever the initial concentrations happens to be. It is Keq that says something about the nature of products and reactions, since it describes their concentrations after =libirum has been reached
what is the value of ΔG at eqilibirum?
ΔG=0
Factors determining spontaneity (negative ΔG)
- intrinsic properties of the reactants and products (Keq)
- concentrations of reactants and products (RTlnQ)
- Temperature
- if the lnQ is negative and the temp is high enough, ΔG will be negative, regardless of the value of ΔGo’
How is Spontaneity related to thermodynamics and kinetics related?
Spontaneity means that a reaction is energetically favorable, but it stays nothing about the rate of the reactions. Thermodynamics will tell you where a system starts and finished but NOTHING about the path traveled to get there. Thus ΔG does not depend on the pathway a reaction takes or the rate of a reaction; it is only a measure of the difference in free energy b/w reactants and products
What do catalysts do?
- only make reaction go faster; NOT changing the free energy
- ONLY deals with kinetics
- increases rate of reactions by
- STABILIZING T.S.
- REDUCING EA
Explain components of reaction coordinate graoh
