Final answer:
The GLUT is an integral membrane protein that assists glucose in moving across a cell membrane through facilitated diffusion. It is crucial for transporting glucose along its concentration gradient, and is activated in the presence of insulin, especially in the case of GLUT4 protein.
Step-by-step explanation:
The GLUT, or glucose transporter, is an integral membrane protein that facilitates the movement of glucose across a cell membrane through a process known as facilitated diffusion. This is necessary because glucose cannot move through the lipid bilayer of the cell membrane without assistance.
GLUT proteins allow glucose to move along its concentration gradient, from areas of higher concentration to areas of lower concentration, until equilibrium is reached. For instance, GLUT4 is a type of glucose transporter that gets activated and moves to the plasma membrane as a result of insulin binding, enabling glucose absorption into cells.
In tissues like the kidney and the small intestine, similar transport proteins like SGLT utilize symport mechanisms to co-transport glucose and sodium ions into cells. This is important in the absorption of dietary glucose. There are different types of GLUTs, each with a specific role in cellular glucose homeostasis and they can work at varying rates, with channel proteins generally facilitating a much faster diffusion than carrier proteins.