What mechanisms facilitate glucose absorption in the intestines?

Glucose absorption in the intestines is facilitated by sodium-glucose transport proteins and facilitated diffusion.

Glucose, a simple sugar, is a primary source of energy for the body. It is absorbed in the small intestine through a process that involves both active transport and facilitated diffusion. The active transport of glucose is facilitated by a group of proteins known as sodium-glucose transport proteins (SGLTs). These proteins use the energy from the sodium ion gradient to transport glucose against its concentration gradient, from the lumen of the intestine into the epithelial cells.

SGLTs are located on the apical surface of the intestinal epithelial cells, which is the side facing the lumen of the intestine. They work by co-transporting two sodium ions along with one glucose molecule into the cell. This process is driven by the sodium-potassium pump on the basolateral surface of the cell, which maintains a high concentration of sodium ions outside the cell. The sodium ions naturally want to move back into the cell, down their concentration gradient. The SGLTs harness this energy to transport glucose into the cell against its concentration gradient.

Once inside the cell, the glucose molecules are transported out of the cell and into the bloodstream by another type of protein known as a glucose transporter (GLUT). This process is an example of facilitated diffusion, where the glucose molecules move down their concentration gradient, from a region of high concentration inside the cell to a region of lower concentration in the bloodstream. The GLUT proteins provide a pathway for the glucose molecules to pass through the cell membrane.

In summary, the absorption of glucose in the intestines is a complex process that involves both active transport and facilitated diffusion, mediated by specific transport proteins. This ensures that the body can efficiently absorb and utilise the glucose obtained from the diet.