Glucose is a so-called simple sugar. It is not linked to other sugar molecules. For this reason, glucose is not broken down by digestive enzymes and passes more quickly through the intestinal wall into the blood. Glucose is an important source of energy, especially for the brain and nerve cells. The hormone insulin, which is produced in the pancreas, is responsible for getting the glucose into the cells.
Exceptions to this are the nerve cells and red blood cells. They can absorb glucose independently of insulin.