Free energy change

Definition

Free energy change, often represented as ΔG, is the amount of energy available to do work in a thermodynamic system at constant temperature and pressure. It determines the spontaneity of a reaction: if ΔG is negative, the reaction can occur spontaneously, while a positive ΔG indicates non-spontaneity. Understanding free energy change is crucial for grasping how biological reactions are coupled and how energy is transferred and utilized in living organisms.

5 Must Know Facts For Your Next Test

1. The free energy change is calculated using the formula ΔG = ΔH - TΔS, where ΔH represents change in enthalpy, T is temperature in Kelvin, and ΔS is change in entropy.
2. Biological systems often utilize ATP hydrolysis to provide the necessary energy to drive reactions with positive ΔG.
3. A negative ΔG value indicates that the reaction releases energy (exergonic), while a positive ΔG value means it requires energy input (endergonic).
4. Standard free energy change (ΔG°) is determined under standard conditions (1M concentration, 1 atm pressure, and 25°C) and helps predict reaction direction.
5. In redox reactions, free energy changes reflect the transfer of electrons and can be harnessed to perform cellular work or synthesize ATP.

Review Questions

• How does free energy change influence redox reactions in living systems?
  • Free energy change plays a pivotal role in redox reactions as it determines whether these reactions can occur spontaneously. In biological systems, redox reactions involve electron transfers that release energy, which is quantified by a negative ΔG. This energy release can be harnessed for vital cellular processes, such as ATP synthesis, highlighting the importance of free energy in metabolic pathways.
• What is the significance of ATP's role in relation to free energy change during phosphorylation?
  • ATP serves as a key energy currency in cells by undergoing hydrolysis to release free energy, which drives phosphorylation reactions. The hydrolysis of ATP typically results in a significant negative free energy change, making it energetically favorable for coupling with other reactions that require an input of energy. This relationship between ATP and free energy change allows cells to efficiently manage energy transfer and support various biochemical processes.
• Evaluate how understanding free energy change contributes to advancements in bioenergetics and metabolic engineering.
  • Understanding free energy change is crucial for advancements in bioenergetics and metabolic engineering because it allows scientists to predict and manipulate metabolic pathways effectively. By analyzing how free energy influences reaction spontaneity, researchers can design engineered pathways that optimize product yields or increase efficiency in microbial production systems. This knowledge helps in developing biotechnological applications that rely on specific energy transformations, paving the way for innovations in sustainable practices and therapeutic strategies.

Related terms

enthalpy: Enthalpy is the total heat content of a system, which includes internal energy plus the product of pressure and volume. It helps determine the heat exchange during chemical reactions.

entropy: Entropy is a measure of disorder or randomness in a system. It reflects the number of ways a system can be arranged, and its increase is often associated with spontaneous processes.

coupled reactions: Coupled reactions involve the pairing of a spontaneous reaction with a non-spontaneous one, allowing the overall process to proceed by using the energy released from the spontaneous reaction to drive the other.