1. Endergonic Reaction
Definition: An endergonic reaction is a chemical reaction that absorbs energy from its surroundings, usually heat. In other words, the products of the reaction have more free energy than the reactants.
Characteristics
– Positive change in Gibbs free energy (Δ G > 0).
– Non-spontaneous in the absence of external energy input.
– Absorbs energy to form products.
– Common in processes that build complex molecules, such as photosynthesis or the synthesis of macromolecules like proteins and nucleic acids.
Example:
Sunlight provides the energy for converting carbon dioxide and water into glucose and oxygen during photosynthesis, making it an endergonic process.
2. Exergonic Reaction
Definition: An exergonic reaction is a chemical reaction that releases energy, usually heat, to its surroundings. The products of the reaction have less free energy than the reactants.
Characteristics:
– Negative change in Gibbs free energy (Δ G < 0).
– Spontaneous and can proceed without external energy input.
– Releases energy as it forms products.
– Common in processes that break down complex molecules, such as cellular respiration.
Example: Cellular respiration is an exergonic process where glucose is broken down to produce energy as ATP.
C6H12O6+6O2→6CO2+6H2O+energy
Overall:
Endergonic and exergonic reactions are interconnected in living systems. The energy released in exergonic reactions can drive endergonic reactions, maintaining the energy balance required for cellular activities.
Together, these concepts contribute to understanding the thermodynamics and energetics of chemical reactions in biological systems.
