Transport of molecules across a membrane

Secondary active transporters

Transports one molecule down its concentration gradient to transport another molecule against its concentration gradient

Symporter

Cotransporter where particles move in same direction

Example of symporter

Na+/Glucose Transporter

Antiporter

Cotransporter where particles move in opposite direction

Example of antiporter

Sodium-potassium pump

F-type ATPase

proton pump in mitochondrial inner membrane to synthesize ATP from ADP

V-type ATPase

Ion pumps inside vesicles (lysosomes/endosomes) that hydrolyse ATP to move ions across the membrane

ABC transporter

ATP-binding cassette transporter

ABC transporter structure

2 transmembrane domains, 2 cytosolic ATP-binding domains, P-glycoprotein

P-glycoprotein (P-gp)

Used in multidrug resistance with hydrolysis of ATP

Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)

Chloride transport protein in epithelial cells

CFTR function

Transports Cl- and Na+ to extracellular space → draws water out, mucus less sticky

Cystic fibrosis

Mutation in CFTR gene → Reduced permeability of Cl- → draws water in, mucus is sticky and obstructs airways