Final answer:
Hexokinase is found in almost every tissue and uses ATP to phosphorylate glucose, trapping it inside the cell; it has a high affinity for glucose. Glucokinase is mainly found in the liver and is active when glucose levels are high.
Step-by-step explanation:
The enzymes hexokinase and glucokinase both function to phosphorylate glucose as part of the glycolysis pathway. Hexokinase is found in nearly every tissue in the body and has a higher affinity for glucose, which allows it to phosphorylate glucose even when levels are low in the body. It uses ATP as the source of phosphate to produce glucose-6-phosphate, which then cannot leave the cell due to the presence of the negatively charged phosphate group. This step not only traps glucose within the cell but also maintains a gradient for glucose to move from areas of high concentration to low. On the other hand, glucokinase is primarily found in the liver and is active when blood glucose levels are high.