Answer: The concentration gradient drives the movement.
Why is no energy required in passive transport?

Diffusion is the net movement of material from an area of high concentration to an area with lower concentration. The difference of concentration between the two areas is often termed as the concentration gradient and diffusion will continue until this gradient has been eliminated. Since diffusion moves materials from an area of higher concentration to an area of lower concentration it is described as moving solutes "down the concentration gradient" (compared with active transport which often moves …

Facilitated diffusion (also known as facilitated transport or passive-mediated transport) is the process of spontaneous passive transport (as opposed to active transport) of molecules or ions across a biological membrane via specific transmembrane integral proteins. Being passive facilitated transport does not directly require chemical energy from ATP hydrolysis in the transport step itself; rather molecules and ions move down their concentration gradient reflecting its diffusive nature.

As mentioned above passive diffusion is a spontaneous phenomenon that increases the entropy of a system and decreases the free energy. The transport process is influenced by the characteristics of the transport substance and the nature of the bilayer. The diffusion velocity of a pure phospholipid membrane will depend on: concentration gradient

Tue Nov 05 2002 13:30:00 GMT-0500 (Eastern Standard Time) · The difference between passive transport and active transport is that the active transport requires energy and moves substances against their respective concentration gradient whereas passive transport requires no cellular energy and moves substances in the direction of their respective concentration gradient.

This is not true. Passive transport relies on the kinetic energy of the substance that is being transported. This kinetic energy is what causes it to move around and (by random chance) cross the membrane. The difference is that active transport actually uses the cell's energy (ATP or ele...

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