Facilitated diffusion is the process of diffusion in which ion or some substances are transported across the membrane by a specific carrier membrane protein. The process does not require the input of energy and is driven by a concentration gradient.
The absorption of simple sugars in small intestine occurs through facilitated diffusion. The polar sugar molecules can not cross the nonpolar inner core of the membrane. Hence, the membrane proteins transport the sugars down the concentration gradients without any input of energy.
