Simple and Facilitated Diffusion

ib bio unit 4

passive and active transport

types of membrane transport

simple diffusion, facilitated diffusion, osmosis

types of passive transport

pump proteins, bulk transport (exocytosis + endocytosis)

types of active transport

the movement of a substance down a concentration gradient

diffusion definition

concentration gradient, distance, temperature, size, polarity

factors impacting diffusion rate

equal concentration of a substance on either side of a semi-permeable membrane, but with constant movement, and in equal amounts and opposite directions. No net movement!

dynamic equilibrium

a type of passive transport where the movement of molecules down a concentration gradient is assisted by transmembrane transport proteins. ex: glucose or ions

facilitated diffusion definition

channel proteins and carrier proteins

types of transmembrane proteins in facilitated diffusion

channel proteins are selective and can be opened and closed. carrier proteins are selective.

two ways to control the process of facilitated diffusion

maintained by hydrophilic/phobic side chains lining the channel and the size of the channel. Many channel proteins only allow 1 type of ion/molecule through.

selectivity of channel proteins

ligand (open/close in response to a ligand binding), and voltage (open/close in response to changes in charge along the membrane)

types of gates channels

When the molecule/ion binds to the carrier protein, the carrier protein undergoes a conformational change and transfers the molecules to the other side of the membrane

carrier protein