This document summarizes different types of transport mechanisms across cell membranes, including facilitated diffusion, passive transport, ion channels, and active transport. Facilitated diffusion and passive transport involve the movement of molecules from high to low concentration areas with or without the help of carrier proteins. Active transport moves materials against a concentration gradient and requires ATP energy, such as the sodium-potassium pump which moves sodium and potassium ions out and in of cells. The document also briefly discusses endocytosis and exocytosis.

1. Facilitated Diffusion & Active Transport