What determines the direction of facilitated diffusion for substances like glucose?

The direction of facilitated diffusion for substances such as glucose is primarily determined by the concentration gradient across the membrane. In facilitated diffusion, molecules move from an area of higher concentration to an area of lower concentration, utilizing specific transport proteins to assist their passage through the cell membrane. This process does not require energy input, as it follows the natural tendency of solutes to distribute evenly in accordance with their concentration.

When considering the movement of glucose, for instance, the transport proteins will allow glucose to enter the cell when its concentration inside is lower than outside, facilitating its movement down the concentration gradient. This essential principle is a key aspect of cellular transport and metabolism, ensuring that cells can efficiently take up necessary nutrients while maintaining homeostasis.