Answer:
The correct answer is:
Transport occurs with the help of membrane proteins
Explanation:
Facilitated diffusion is the passive (no energy required) movement of molecules across a cell membrane, with the aid of a membrane protein. energy in form of ATP or GTP is not required since molecules are moving down their concentration gradient.
The need for facilitated diffusion occurs when substances cannot successfully cross the phospholipid bilayer of the cells membrane on their own either due to their polarity or large size. The proteins in facilitated diffusion are tthose that act as carriers and those the form the channels across the membrane, through which the diffusion occurs. Examples of where facilitated diffusion is seen is in the transport of glucose (relatively large molecule) across the cell membranes, with the help of the glucose transporter and the transportation of water molecules across the cell membrane through aquaporins.
