Exergonic and Endergonic Reactions |
Each state has an associated Entropy (S), Enthalpy (H) and Free Energy (G)
S1 = entrophy of state 1
S2 = entrophy of state 2
H1 = enthalpy of state 1
H2 = enthalpy of state 2
G1 = free energy of state 1
G2 = free energy of state 2
The relationship between these three parameters
is given by the equation
(G2-G1) = (H2-H1) - T (S2-S1)
Exergonic reactions
If the free energy of state1 is greater that the free energy
of state 2 then the value of the free energy change for the reaction is a negative
number. (-G)
In an exergonic reaction the change is free energy is represented by a negative number (-G), indicating free energy is released during the reaction
free
energy is liberated during the reaction.
This represents energy that can be used to
do biological work
the
reaction will occur spontaneously. However, the reaction does not necessarily
occur at a great rate. This is where enzyme come in.
In an endergonic reaction the free energy of the initial state is lower than the free energy of the final state.
This kind of reaction is not termed a spontaneous reaction. In order to go from the initial state to the final state a considerable amount of energy must be imparted to the system. These kinds of reactions are associated with a positive number (+G).
free
energy is liberated during the reaction.
This represents energy that can be used to
do biological work
the
reaction will occur spontaneously. However, the reaction does not necessarily
occur at a great rate. This is where enzyme come in.
Enzymes increase the rates of exergonic
reactions
return to how enzymes work