Exergonic reactions

Definition

Exergonic reactions are chemical processes that release energy to the surroundings, typically in the form of heat, as they proceed toward equilibrium. These reactions have a negative change in Gibbs free energy ($$ riangle G < 0$$), indicating that they are spontaneous and can occur without the need for external energy input. In biological systems, exergonic reactions play a crucial role in driving cellular processes and are often coupled with endergonic reactions to provide the energy needed for tasks such as biosynthesis and muscle contraction.

5 Must Know Facts For Your Next Test

1. Exergonic reactions are characterized by a decrease in free energy, making them energetically favorable and spontaneous.
2. These reactions can occur spontaneously under standard conditions but may still require an initial activation energy to start.
3. Common examples of exergonic reactions include cellular respiration and the breakdown of glucose.
4. The energy released from exergonic reactions can be harnessed to power endergonic reactions, allowing cells to perform work.
5. The concept of coupling exergonic and endergonic reactions is fundamental to understanding metabolic pathways in living organisms.

Review Questions

• How do exergonic reactions relate to the concept of Gibbs free energy, and why is this relationship important for biological systems?
  • Exergonic reactions are defined by having a negative change in Gibbs free energy ($$ riangle G < 0$$), which indicates that they can occur spontaneously without additional energy input. This relationship is crucial for biological systems because it allows these reactions to drive essential cellular processes while conserving energy. By understanding Gibbs free energy, we can predict which reactions will occur naturally and how they contribute to overall metabolic pathways.
• Discuss how exergonic reactions are coupled with endergonic reactions in metabolic processes.
  • Exergonic reactions release energy that can be utilized by endergonic reactions, which require an input of energy to proceed. This coupling is a key principle in metabolism, where the energy produced from processes like ATP hydrolysis is used to power biosynthetic pathways or muscle contractions. Such coupling ensures that the overall reaction pathway remains energetically favorable, allowing cells to efficiently convert and utilize available energy.
• Evaluate the significance of exergonic reactions in cellular respiration and how they impact energy balance in living organisms.
  • Exergonic reactions are vital during cellular respiration, as they facilitate the breakdown of glucose and other molecules, releasing energy that is subsequently stored as ATP. This process not only provides the necessary energy for various cellular functions but also helps maintain an energy balance within living organisms. By understanding the role of exergonic reactions in cellular respiration, we see how they enable organisms to thrive by efficiently managing their energy needs and supporting life-sustaining processes.

Related terms

Gibbs free energy: A thermodynamic quantity that represents the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure.

endergonic reactions: Reactions that require an input of energy to proceed, resulting in a positive change in Gibbs free energy ($$ riangle G > 0$$).

ATP hydrolysis: The process by which adenosine triphosphate (ATP) is broken down into adenosine diphosphate (ADP) and inorganic phosphate, releasing energy that can be harnessed for cellular work.