Final answer:
Hexokinase specifically reacts with one of the two isomers of glucose, catalyzing the phosphorylation to produce glucose-6-phosphate, thus maintaining glucose concentration gradients.
Step-by-step explanation:
The enzyme hexokinase is so specific that it reacts with only one of the two isomers of glucose. Hexokinase catalyzes the phosphorylation of six-carbon sugars and uses ATP as the source of phosphate to produce glucose-6-phosphate. This reaction not only traps the glucose molecule within the cell but also maintains a concentration gradient, allowing glucose to flow from high concentrations in the blood to lower concentrations in the tissues, where it is used or stored. Indeed, hexokinase has a high affinity for glucose and converts it at a faster rate than glucokinase, which is particularly crucial for tissues that require glucose more when the body's levels are low.