Which type of transport across the cell membrane does not require energy?

Facilitated diffusion is a type of passive transport that occurs when molecules move across the cell membrane with the help of transport proteins. This process does not require energy because it relies on the concentration gradient, meaning substances move from an area of higher concentration to an area of lower concentration.

In facilitated diffusion, specific proteins in the cell membrane assist larger or polar molecules, such as glucose or ions, in crossing the lipid bilayer. These proteins allow molecules to pass through more easily than they would alone, but the movement is still driven by the natural tendency of molecules to spread out evenly in a solution.

This contrasts with active transport, which requires energy in the form of ATP to move substances against their concentration gradient. Exocytosis and endocytosis are forms of bulk transport that involve the use of energy to move particles in and out of the cell within vesicles. Thus, facilitated diffusion is unique among the choices given in that it does not require energy expenditure by the cell.