why carrier proteins are required for transfer of polar molecules through the bilayered lipid
Transport across plasma membrane:
1. Passive transport − It does not require energy. Hence, neutral solute moves by diffusion, along the concentration gradient. Water moves through osmosis. Polar molecules cannot move through the lipid bilayer. It needs a Facilitated diffusion, and hence carried out by carrier proteins.
2. Active transport − It requires energy for transport against the concentration gradient.