Thermodynamics Flashcards
a reaction that releases heat is
exothermic
a reaction that absorbs heat is
endothermic
when H is negative
its exothermic - spontaneous
when H is positive
it’s endothermic - non-spontaneois
Reactions that increase entropy (+S) tend to be
______
spontaneous
reactions that release heat (-ΔH) tend to be
spontaneous
measures the energy difference between the products and reactants and takes into account both entropy and enthalpy
gibbs free energy
H stands for
Enthalpy change =
heat absorbed or
released
T stands for
Temperature
S stands for
enthalpy
A negative ΔG =
spontaneous reaction
A positive ΔG =
a nonspontaneous reaction
(-) ΔG
exergonic
(+) ΔG
endergonic
what is G dependent on?
temperature, pH, relative concentrations of products and reactants
Standard Gibbs free energy is calculated at ____ (room
temperature), at a pH of __, at __ M of each reactant and
product -> ΔGo
Standard Gibbs free energy is calculated at 298 K (room
temperature), at a pH of 7, at 1 M of each reactant and
product à ΔGo
The following is the first reaction of glycolysis:
§ Glucose + Pi Glucose-6-phosphate
* ΔGoʼ = 12 kJ/mol
Note the positive ΔGoʼ
How is it possible that a reaction with a
(+) ΔGoʼstill occurs in our bodies – all the
time?
This is the whole “rationale” for why the body
phosphorylates ATP (and dephosphorylates it) as a
source of energy currency
- The high-energy phosphodiester bond, when broken,
has a negative ΔG - That energy can be coupled to another reaction with a
positive ΔG - The net reaction is exergonic…
- if the ΔG of ATP is “negative enough” to counteract
the endergonic ΔG of the coupled reaction
