Simple diffusion does not require energy: facilitated diffusion requires a source of ATP. Simple diffusion can only move material in the direction of a concentration gradient; facilitated diffusion moves materials with and against a concentration gradient.

Facilitated diffusion requires membrane proteins to transport biological molecules. Simple diffusion is one that occurs unassisted by membrane proteins. Since membrane proteins are needed for transport in facilitated diffusion, the effect of temperature is often more pronounced than in simple diffusion.

Facilitated diffusion can cause movement both towards and against concentration gradient. Concentration gradient is required.

Facilitated diffusion therefore allows polar and charged molecules, such as carbohydrates, amino acids, nucleosides, and ions, to cross the plasma membrane. Two classes of proteins that mediate facilitated diffusion are generally distinguished: carrier proteins and channel proteins.

Unlike simple diffusion, facilitated diffusion requires energy expenditure by the cell. (

Channel proteins, gated channel proteins, and carrier proteins are three types of transport proteins that are involved in facilitated diffusion. A channel protein, a type of transport protein, acts like a pore in the membrane that lets water molecules or small ions through quickly.

The main factors affecting the process of facilitated diffusion are:

• Temperature- As the temperature increases, the movement of the molecules increases due to an increase in energy.
• Concentration- The movement of the molecules takes place from the region of higher concentration to lower concentration.

Why Is Facilitated Diffusion Necessary? Cells need processes like facilitated diffusion because the cell membrane is permeable to only a select few types of molecules. The molecules that are allowed to move across the cell membrane must be non-polar molecules which are small in size.

Some large, polar, electrically charged or lipid-insoluble molecules require assistance to diffuse across the plasma membrane. Facilitated diffusion using carrier proteins or ion channels allows these important molecules (like glucose) to cross the membrane.

Basic Features. The bilayer consists of lipids, therefore only lipid-soluble molecules can pass through it. This is mainly small polar uncharged molecules and small hydrophobic molecules. Facilitated diffusion is a passive process that requires no use of external energy.

Diffusion requires that particles have kinetic energy. Diffusion is a process that allows particles to move from areas of high concentration to areas of lower concentration. As long as particles are not at a temperature of 0K (absolute zero) they have kinetic energy (energy of movement).

Facilitated diffusion is a type of passive transport. Facilitated diffusion is like normal diffusion, except that it happens through special protein channels and carrier proteins. These integral membrane proteins are necessary because charged particles and large, polar molecules cannot easily make their way through the plasma membrane.

These integral membrane proteins are necessary because charged particles and large, polar molecules cannot easily make their way through the plasma membrane. However, facilitated diffusion is still a form of passive transport because the molecules are moving from an area of high concentration to an area of low concentration.

Metabolic energy (such as from ATP) is required for active transport of molecules and/or ions across the membrane and to establish and maintain concentration gradients. The Na + /K + ATPase contributes to the maintenance of the membrane potential. Just to send a signal to your muscles, an entire system of membrane proteins is needed!

Facilitated Diffusion This is the movement of specific molecules down a concentration gradient, passing through the membrane via a specific carrier protein. Thus, rather like enzymes, each carrier has its own shape and only allows one molecule (or one group of closely related molecules) to pass through. Selection is by size; shape; charge.