Provide an example of the positive and negative free energy of a chemical reaction.

A positive free energy change indicates an endergonic reaction, while a negative change indicates an exergonic reaction.

Chemical reactions involve the breaking and forming of chemical bonds, which requires energy. The free energy change (ΔG) of a reaction determines whether it is energetically favourable or not. A negative ΔG indicates that the reaction is exergonic, meaning that it releases energy. This energy can be harnessed to do work, such as powering cellular processes. For example, the breakdown of glucose during cellular respiration has a negative ΔG, releasing energy that is used to produce ATP.

On the other hand, a positive ΔG indicates that the reaction is endergonic, meaning that it requires energy input to occur. This energy is typically supplied by ATP, which is hydrolysed to provide the necessary energy. An example of an endergonic reaction is the synthesis of glucose during photosynthesis. This process requires energy from sunlight, which is captured by chlorophyll and used to power the synthesis of glucose from carbon dioxide and water.

While exergonic reactions are generally favourable, endergonic reactions are necessary for life processes such as growth and repair. By coupling endergonic reactions to exergonic ones, cells are able to maintain a constant supply of ATP to power their metabolic processes. Overall, the free energy change of a reaction is a crucial factor in determining its feasibility and importance in biological systems.