Facilitated Diffusion (2B)

Facilitated Diffusion

Movement of charged or polar particles across the phospholipid bilayer with the help of proteins (carrier/channel)

Carrier Proteins

Proteins that bind to specific molecules, undergo shape changes, and shuttle the molecules across the membrane.

• transports: simple sugars (mono- and disaccharides), amino acids, nucleosides

Channel Proteins

Proteins that form open channels for the continuous passage of particles across a membrane (can be gated)

• transports: ions (sodium, potassium, calcium, and chloride), water (aquaporins)

Concentration Gradient

The difference in concentration of a substance across a space, dictating the direction of particle movement during diffusion.

Aquaporins

Channel proteins that facilitate the transport of water across cell membranes. Quicker rate of water movement than during osmosis where it takes a while for water to scooch in between the phospholipid bilayer.