Endergonic vs Exergonic
For the purpose of chemistry, the universe is divided into two parts. The part in which we are interested is called a system, and the rest is called the surrounding. A system can be an organism, a reaction vessel or even a single cell. There are boundaries between a system and the surrounding. The scope of the system is defined by these boundaries. Sometimes matters and energy can be exchanged through these boundaries.
Energy is the capacity to do work. In a system, energy can do work and, in this process, energy can be changed to other forms such as heat, sound, light etc. When the energy of a system changes as a result of a temperature difference between the system and the surrounding we say that energy has been transferred as heat. A chemical reaction can be considered as a system. Chemical reaction is a process, where one or more compounds are converted to a new set of compounds through a series of changes. When the reaction proceeds, there can be an energy transfer from surrounding to the system or vice versa. Some of these reactions are spontaneous, and some are not. All the reactions happening in the environment are not spontaneous, but we see these non-spontaneous reactions take place naturally. That is because, non-spontaneous reactions are coupled to the spontaneous reactions and they are driven by the energy of the spontaneous reactions.
What is Endergonic?
The word “ender” has derived from the word “endo” which means “within”. Therefore, endergonic means absorbing energy in the form of work. So, in an endergonic reaction, surrounding supplies energy into the system. Further, the products will have a higher energy than the reactants. Endergonic reaction is considered to be nonspontaneous or unfavorable. If this energy transfer takes place in a constant pressure and temperature, the standard Gibbs free energy will be positive. Thus, the equilibrium constant for an endergonic reaction is less than one. Photosynthesis is an endergonic reaction which takes places in the natural environment. For photosynthesis, energy is supplied by sunlight. In the human body, when endergonic reactions are taking place, most of the time the energy is supplied by the ATP. So, endergonic reactions are coupled to ATP hydrolysis reactions.
What is Exergonic?
Exergonic means releasing energy in the form of work. In these reactions, energy is released from the system to the outside. Exergonic reactions are favorable and spontaneous. Because the energy is released during the reaction, the products contain less energy than the reactants. Therefore, the enthalpy change (∆H) becomes negative. Moreover, if the transfer is carried out in constant pressure and temperature, standard Gibbs free energy will be a negative value.
What is the difference between Endergonic and Exergonic?
• Endergonic means absorbing energy in the form of work whereas Exergonic means releasing energy in the form of work.
• Endergonic reactions are non-spontaneous and unfavorable, whereas exergonic reactions are spontaneous and favorable.
• The standard Gibbs free energy will be positive in endergonic reactions in contrast to exergonic reactions.
• In exergonic reactions, the products contain less energy than the reactants but, in endergonic reactions, products contain higher energy than the reactants.