membrane transport Flashcards
what do membranes do?
compartmentalize!
what are lipid bilayers permeable to?
some non-polar compounds, polar molecules require protein mediated transport
what must spontaneous passive transport be?
down a concentration gradient, active transport is up a concentration gradient which requires energy
what can transport be facilitated by?
channels!
what are the different types of facilitated channels?
non-stoichiometric
always passive
selective
gated
what are transporters?
stoichiometric
passive or active
specific
regulated
what does passive transport use?
channels (fast), transporters are slower and concentration gradients (down spont)
what does active transport use?
energy!! transporters!! using ATP coupled transport
how are ions transported?
pumps!
how is the large Na+/K+ gradient maintained?
by the Na, K-ATPase pump
even thought he cell must be a neutral charge what happens?
K+ leak channels allow some K ions to exit until the concentration gradient is balanced this creates a voltage difference across the bilayer of -70 mV (membrane potential–action potential) -ve inside relative to outside
What is the transport of ions subject to?
both concentration and voltage gradients
what are the different kinds of transport proteins?
uniport: one substance at a time
symport: two substances at a time
antiport: moves two different substances in different directions across a membrane
CONFORMATIONAL CHANGE YO
what are the topological relationships in a cell?
some things you need to a pass a membrane to get to
there is the cytosol and the extracellular space
what are protein destinations decided by?
embedded target sequences
