A classic example of an endergonic reaction is a synthesis reaction, where simple molecules combine to form complex compounds. An endergonic reaction requires the input of free energy to initiate the process.
Thermodynamics delves into the correlation between energy and work. In chemistry, the term "energetics" is more commonly used to refer to chemical reactions involving energy. Exergonic reactions release free energy from the breakdown of complex molecules into simpler substances. The energy given off from these processes is used to drive endergonic reactions. The synthesis of proteins from amino acids and the production of carbohydrates from sugar molecules are additional examples of endergonic reactions.