They are non-spontaneous. The change in standard free energy in an exergonic reaction is graphed below. Initially, the energy of the reactants, labeled G reactants , is high and the final G products , the energy of the products of the reaction is low. Endergonic reactions have K eq values less than one. Endergonic reactions tend to reach equilibrium when the concentration of reactants is still high and the concentration of products is low.
Endergonic reactions are important to many cell processes.
Endergonic reactions may be 'pushed' forward by coupling them with exergonic reactions. The energy released from the exergonic reaction can be used to drive the endergonic reaction. Endergonic reactions may also be 'pulled' forward by removing the products of the reaction as fast as they form, so that the reaction is prevented from reaching its equilibrium point. Chemical reactions, both spontaneous and non-spontaneous, require an initial input of energy, the energy of activation, to begin the reaction. This energy is needed to bring reactant molecules into position and condition for reaction.