Membrane Transport Flashcards
permeable molecules
gases & small uncharged polar molecules
impermeable molecules
large uncharged polar molecules, ions, & charged polar molecules
Classes of Membrane Transport Proteins
ATP-powered pumps, ion channels, & transporters (uniporter, symporter, & antiporter)
ATP-powered pumps
move cargo against concentration gradient; ATP dependent; ATP binding site(s) on cytosolic face of pump
Ion channels
move ions down their concentration gradient; can be gated or not; NOT ATP dependent
Uniporter
moves a single molecule down it’s concentration gradient; uses potential energy from gradient
Symporter
uses the energy from moving one molecule down it’s concentration gradient to move another molecule against it’s concentration gradient; both move through protein in the same direction
Antiporter
uses the energy from moving one molecule down it’s concentration gradient to move another molecule against it’s concentration gradient; molecules move in opposite directions through the protein
GLUT1 Transporter
uniporter moves glucose down concentration gradient through conformation change; cell changes glucose to glucose-6-phosphate to ensure glucose is not returned to the outside of the cell
3 ATP-powered pumps
P-Class, V-Class, & F-Class
P-Class Pump
composed of 2 alpha & 2 beta subunits; alpha unit becomes phosphorylated during transport
V-Class Pump
pumps protons against the concentration gradient; no subunit phosphorylation
F-Class Pump
pumps protons along gradient in order to generate ATP (final step of ATP generation within the mitochondria)
ABC Superfamily
examples: flippase & role in chemo resistance (pump our drug before work can be done)
Ca2+ transport into SR of Muscle Cells
muscle impulses release Ca2+ from lumen through votage gated channel (against gradient) into sarcoplasmic reticulum
