can someone clearly explain the difference between: delta G delta G prime delta G naught delta G naught prime learning all this in biochemistry and its a bit confusing
The Correct Answer and Explanation is:
ΔG (Gibbs Free Energy Change):
ΔG represents the actual change in free energy during a reaction under real, cellular conditions, which may include non-standard concentrations of reactants and products. It determines whether a reaction will proceed spontaneously. If ΔG is negative, the reaction is exergonic (spontaneous); if positive, the reaction is endergonic (non-spontaneous). This value is dependent on temperature, pressure, and the actual concentrations of reactants and products.
ΔG° (Standard Gibbs Free Energy Change):
ΔG° refers to the change in free energy under standard thermodynamic conditions, which are defined as 1 M concentrations of all reactants and products, 1 atm pressure, and a temperature of 25°C (298 K). It gives an intrinsic measure of a reaction’s tendency to occur but does not reflect biological conditions. This is used mostly in general chemistry and physics.
ΔG′ (Biological Gibbs Free Energy Change):
ΔG′ is the free energy change under biological conditions, but without the constraint of standard pH. It still reflects actual cellular concentrations and temperatures, but pH may vary depending on the context. It’s not as commonly used in textbooks but may appear in specific experimental setups.
ΔG°′ (Standard Free Energy Change at pH 7):
ΔG°′ is the biochemical standard free energy change, measured under standard conditions except the pH is set at 7.0 (instead of 0 as in ΔG°). This modification makes it more relevant for biological systems, where most processes occur around neutral pH. This value is used widely in biochemistry to assess whether a reaction tends to proceed under cellular conditions.
In summary:
- ΔG = actual free energy change in the cell
- ΔG° = standard free energy change (1 M, pH 0)
- ΔG′ = biological, but not standardized pH
- ΔG°′ = standard biological free energy change (1 M, pH 7)
Understanding these distinctions is critical in biochemistry because biological systems operate under specific, often non-standard conditions.
