Filtration

Facilitated Diffusion
This is the passage of particular molecules through the membrane using a particular carrier protein and a concentration gradient. Thus, each carrier has its structure and only permits one molecule (or one set of closely related compounds) to pass through, similar to how enzymes do.
Selection is based on size, shape, and charge. Glucose and amino acids are typical substances that enter or exit cells in this manner.
It uses no energy from the cell and is passive. The concentration gradient of glucose will be maintained high if the molecule is altered upon entry into the cell (glucose + ATP → glucose phosphate + ADP), resulting in constant one-way traffic.