Final answer:
The least spontaneous reaction among the given options is Reaction D: Fructose-6-phosphate → Fructose-1,6-bisphosphate. This reaction has a large positive standard Gibbs free energy (∆G°) value, indicating that it is not favorable or spontaneous under standard conditions.
Step-by-step explanation:
The least spontaneous reaction among the given options is Reaction D: Fructose-6-phosphate → Fructose-1,6-bisphosphate. This reaction has a large positive standard Gibbs free energy (∆G°) value, indicating that it is not favorable or spontaneous under standard conditions.
In glycolysis, the conversion of Fructose-6-phosphate to Fructose-1,6-bisphosphate is an energy-consuming process, requiring the input of ATP. This conversion is catalyzed by the enzyme phosphofructokinase-1.
On the other hand, Reactions A, B, and C involve the conversion of phosphorylated sugar intermediates to other phosphorylated sugar intermediates and generally have lower positive or even negative ∆G° values, indicating their greater spontaneity.