Final answer:
Phosphorylation of glucose by hexokinase helps to retain glucose inside the cell by converting it into glucose-6-phosphate, which cannot cross the plasma membrane, thereby ensuring its availability for metabolic processes like glycolysis.
Step-by-step explanation:
The phosphorylation of glucose by hexokinase serves the purpose of retaining glucose inside the cell. Hexokinase uses ATP to add a phosphate group to glucose, converting it to glucose-6-phosphate. This phosphorylation is vital because it makes the molecule more reactive and unable to cross the hydrophobic interior of the plasma membrane, thus trapping it within the cell. This mechanism is crucial for cellular metabolism, specifically for glycolysis to proceed. It ensures that the glucose is available for the cell to use and is not lost to the extracellular space. Hexokinase is found in nearly every tissue in the body and plays a significant role in regulating glucose levels in the tissues by maintaining a concentration gradient.