The transaminase transfer of an amine group from alanine to α-ketoglutarate to form pyruvate and glutamate has a change in Gibb’s free energy (ΔG) of 1.9 kJ/mol. What does this ΔG value tell you about the reaction?

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BlackTom AI · Accepted Answer

To start, we’ll interpret what a ΔG value in the vicinity of zero implies for a biochemical transformation.
Option a: 'The reaction is non-spontaneous and requires input of energy.' A small positive ΔG like +1.9 kJ/mol does not indicate a strongly non-spontaneous, energy-demanding process; such a value is too small to claim the reaction constantly requires energy input. Reactions with large positive ΔG are the ones that are definitely non-spontaneous under standard conditions.
Option b: 'The reaction is spontaneous and releases energy.' A negative ΔG would indicate spontaneity and energy release. Since the given ΔG is +1.9 kJ/mol (positive), this statement is inconsistent with the sign and thus incorrect.
Option c: 'The reaction cannot occur under physiological conditions.' A ΔG that is small and near zero typically means the reaction is readily reversible under cellular conditions, not that it is prohibited. Therefore this claim about feasibility under physiological conditions is unfounded.
Option d: 'The reaction is close to equilibrium and occurs in both directions.' A ΔG near zero (in magnitude) is characteristic of reactions near equilibrium, where the forward and reverse rates are similar and the reaction can proceed in either direction depending on substrate/product concentrations. In transaminase reactions, such near-equilibrium behavior is well-documented, reflecting the mutual interconversion of substrates and products.
In summary, the small positive ΔG suggests the reaction lies near equilibrium and is reversible, which aligns best with option d, while the other choices misinterpret the sign and magnitude of ΔG or misstate feasibility and directionality.

The transaminase transfer of an amine group from alanine to α-ketoglutarate to form pyruvate and glutamate has a change in Gibb’s free energy (ΔG) of 1.9 kJ/mol. What does this ΔG value tell you about the reaction?

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