Question

Why are proteins able to pass through the plasma membrane but lipids cannot?

Answer 1

PLASMA MEMBRANE: It is the biological membrane that separates interior of the cell to the external environment.

• Structure of Plasma Membrane is Lipid bilayer with phospholipids of hydrophobic and Hydrophilic heads with tails.The Hydrophobic Heads deals with the external environment and hydrophilic heads deals with the internal environment.
• Permeability is the rate of exchange of substances with diffusion.As the plasma membrane is hydrophobic it allows electrically neutral substances,non polar solutes based on the size of the substance,Solubility and molarity.
• The Proteins pass through the plasma membrane because they do not have direct interaction with hydrophobic ends. .Transporter proteins are one of the proteins which help in transporting of non permeable substances by binding to them.The channels present in the plasma membrane are also proteins which easily permeable for transporting substances through facilitated diffusion.
• The lipids are polar solutes and large in size so they cannot travel through plasma membrane and they need a transporter protein for their permeability.