Cells and Cell Structure

Question

Permeability is the condition of being capable of materials flow into and out of a membrane. The permeability of a cell membrane is determined by how easily a molecule can diffuse across the membrane. Usually, only molecules that are fat-soluble can permeate across a cell membrane. Why is this the case?

Answer 1

Transport across the cell membrane occurs through passive transport or active transport. Passive transports allows only small, nonpolar molecules and ions to slip through the membrane's phospholipid bilayer. For active, transport, proteins embedded within the membrane are used to transport molecules from one side to the other. For fat soluble molecules, in particle, the general understanding is they use passive transport when there is a concentration gradient present.