The Phospholid Cell Membrane In The Exchange Of Materials.?

Question

Some substances are essential to the survival of the cell, but do not pass through the phospholipid cell membrane readily.

What are the enhancements on the cell membrane that allow these substances to pass through the phospholipid cell membrane? What are the properties of these enhancements and explain briefly how they complement the phospholipid cell membrane in the exchange of materials.

Answer 1

Obviously a homework assignment.  Look up active transport, facilitated diffusion, membrane transport, etc.  There are proteins embedded in the phospholipid bilayer of the membrane that are "enhancements" that assist in the movement of certain molecules across the membrane.