Exergonic reaction

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Exergonic reaction

An exergonic reaction is a type of chemical reaction where the change in the Gibbs free energy (ΔG) is negative, indicating that the reaction releases energy to its surroundings. This release of energy can be in the form of heat, light, or other forms of energy. Exergonic reactions are spontaneous, meaning they can occur without the input of additional energy.

Thermodynamics

In thermodynamic terms, an exergonic reaction is characterized by a decrease in the Gibbs free energy of the system. The equation for Gibbs free energy is:

ΔG = ΔH - TΔS

where:

• ΔG is the change in Gibbs free energy,
• ΔH is the change in enthalpy,
• T is the temperature in Kelvin,
• ΔS is the change in entropy.

For an exergonic reaction, ΔG < 0, which means the reaction is thermodynamically favorable.

Examples

Common examples of exergonic reactions include:

• Cellular respiration: The process by which cells convert glucose and oxygen into carbon dioxide, water, and energy.
• Combustion: The burning of fuels such as wood, coal, and gasoline to produce heat and light.
• ATP hydrolysis: The breakdown of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and an inorganic phosphate, releasing energy that is used by cells for various functions.

Biological Significance

Exergonic reactions play a crucial role in biological systems. They provide the necessary energy for various cellular processes, including metabolism, muscle contraction, and nerve impulse transmission. The energy released from exergonic reactions is often harnessed by cells to drive endergonic reactions, which require an input of energy.

Comparison with Endergonic Reactions

Exergonic reactions are the opposite of endergonic reactions, which have a positive ΔG and are non-spontaneous. Endergonic reactions require an input of energy to proceed. In biological systems, exergonic and endergonic reactions are often coupled together to ensure that the overall process is energetically favorable.

See Also

• Endergonic reaction
• Gibbs free energy
• Thermodynamics
• Metabolism
• ATP