How Does Glucose Enter a Cell?

According to Prentiss Hall, while the epithelial cells of the intestine transport glucose using active transport, the red blood cells use facilitated diffusion across a membrane. The method of active transport required depends on the environment of the cell.

The epithelial cells that line the intestine are responsible for bringing glucose from digested food into the body, while preventing the flow of glucose back into the intestine. Regardless of the concentration of glucose in the gut, it is essential that the flow remain in this direction. While active transport is less energy efficient, it prevents glucose from flowing back into the gut when the intestines are empty and curbs the loss of short-term energy reserves.

In the kidneys, the body uses active transport to preserve glucose, moving it from the lower concentration in the filtrate back to a higher concentration in the blood so that the body does not excrete it in the urine.

With most other tissues, including red blood cells, facilitated diffusion provides a more energy-efficient means of transport. The body regulates glucose levels in the blood to keep it higher than the concentration in the cells. Once glucose enters the cell, the cell converts it into chemicals to provide energy, keeping glucose levels lower than those in the blood. The process allows facilitated diffusion to keep glucose flowing in the correct direction.