These reactions have a net release of energy so they are called exergonic reactions. Examples of catabolic reactions would be hydrolysis and the reactions involved in cellular respiration. There is a net input of energy so these reactions are called endergonic . Products of endergonic reactions have higher potential energy. Examples would be biosynthetic reactions and dehydration synthesis.
All chemical reactions require an initial input of energy called the energy of activation .
Exergonic Endergonic Often, reactions are coupled, so the energy released from an exergonic reaction is used to drive an endergonic one. For example, the sun releases energy needed to drive photosynthesis. More energy is released from the exergonic reaction than can be captured in an endergonic reaction, and the extra energy is lost as heat remember the 2 nd Law of Thermodynamics. Energy given off from food catabolism is used to drive endergonic reactions such as synthesis of complex molecules. Sometimes, coupled reactions occur in different places, so energy from the exergonic reaction must be transferred to the location of the endergonic reaction.