The correct answer is: D.carrying messages to other cells
• Allowing polar molecules to enter the cell - Membrane proteins can be involved in transport. This kind of proteins are called channel proteins and usually are integral, transmembrane proteins of the membrane (span across the bilayer). Channel proteins are responsible for facilitated diffusion and active transport of the molecules.
• Recognizing other types of cells- Membrane proteins may function as markers for cellular identification (recognition) and may connect and join two cells together
• Receiving messages – Membrane proteins are often receptors for peptide hormones and thus involved in signal transduction.
