Coupled Reactions
Coupled reactions involve pairing a spontaneous reaction (ΔG < 0) with a non-spontaneous reaction (ΔG > 0) to drive the latter forward. This concept is essential in biological and chemical systems where energy transfer is required.
How Coupled Reactions Work
- The overall ΔG for coupled reactions is additive:
ΔG_total = ΔG_spontaneous + ΔG_non-spontaneous - A non-spontaneous reaction can proceed if it is coupled with a reaction that releases enough free energy to make ΔG_total negative.
Common Examples
- ATP Hydrolysis:
- ATP → ADP + Pi (ΔG < 0)
- Drives many non-spontaneous cellular processes like muscle contraction or active transport.
- Redox Reactions in Metabolism:
- Electron transfer from a high-energy donor to a lower-energy acceptor provides energy to drive other biochemical reactions.
Key Points
- Coupled reactions are crucial for energy management in chemical and biological systems.
- They allow reactions that would otherwise not occur spontaneously to proceed efficiently.
- Understanding ΔG and energy coupling is fundamental for thermodynamics and biochemistry applications.
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