What is facilitated diffusion
Facilitated diffusion is a passive process by which substances move across cell membranes with the help of specific transport proteins. It occurs down the concentration gradient, meaning that substances move from an area of higher concentration to an area of lower concentration.
To understand facilitated diffusion, you need to understand the structure of the cell membrane. The cell membrane is made up of a lipid bilayer, which forms a barrier that only allows certain substances to pass through. However, some substances are too large or polar (charged) to pass through the membrane freely.
In facilitated diffusion, specific proteins called carrier proteins or channel proteins assist in the movement of these larger or polar substances across the membrane. Carrier proteins bind to specific substances on one side of the membrane and undergo a conformational change, allowing the substance to be transported across the membrane to the other side. Channel proteins, on the other hand, form pores or channels in the membrane, allowing the substances to pass through.
One key characteristic of facilitated diffusion is that it does not require any energy input from the cell. The substances move passively, driven by the concentration gradient. However, the process can be regulated by the cell, as the number and activity of the transport proteins can be adjusted to control the rate of diffusion.
Overall, facilitated diffusion is an important mechanism for the transport of substances across cell membranes, particularly in cases where molecules are too large or polar to diffuse freely through the lipid bilayer.