crossing membranes Flashcards
how do solutes cross membranes?
simple diffusion
facilitated diffusion
active transport
what molecules can move freely through the membrane?
small uncharged molecules
what is simple diffusion?
unassisted movement down the gradient
what is facilitated diffusion?
protein mediated movement down the gradient (no energy, only high-low)
what are the two main types of facilitated diffusion?
channels and carriers (both proteins)
how do carrier proteins work?
they alternate between two conformational states, can transport one or two molecules each
what are the two types of carrier proteins?
antiporters (two molecules in different directions) and symporters (two molecules in same direction)
how do channel proteins work?
forming hydrophilic transmembrane channels
what are the three types of channel proteins?
ion channels (specific)
porins (unspecific)
aqauporins (water)
what opens ion channel gates?
voltage
ligand
temperature
pressure
what is an example of an ion channel?
potassium channels - potassium interacts with oxygen while sodium are smaller and can’t interact with oxygen so cant make it through
why is passing ions important?
it changes the polarization which cells can read and use it as an intracellular signal
what do ligand gates ion channels do?
convert chemical signals into the cell
what do voltage gated sodium channels do?
transmit signals in a wave throughout the nervous system
what are porins?
transmembrane proteins allowing rapid passage of various solutes
