lecture 11 membrane transport Flashcards
cell membranes are ________ permeable
selectively
review worksheet about what solutes than can cross a phospholipid bilayer
ok
what type of molcules pass directly between lipids forming the membrane
small hydrophobic and small uncharged polar molcules
small molecules that cannot use simple diffusion to cross a cell membrane use what
transporter proteins and facilitated diffusion
what is facilitated diffusion
diffusion with help (from the transporter protein
what is faciliatetd diffusion mediated by
channel prpteins and carrier proteins
what is channel protein mostly used by
ions
what are carrier proteins mostly used by
other small solutes
how do channel proteins work
make tunnel to pass through membrane
how do carrier proteins work
chnage coformation allow their solute to cross the membrane
most channel proteins are what
gated, which means they open and close in response to cellular conditions
examples gated channel protein
-binding of ligand
-change in electrical gradient
-mechanical trigger
-light activation
what do diffusion rates of ions through ion channels depend on
electrochemical gradients
typical electrochemical gradient of cellular conditions
membrane potential negative inside
active transport
movement of solutes against their concentration gradient
what does active transport require
energy, making system more organized
what is concentration gradient in terms of ions
electrochemical gradient
examples of active transport
coupled transport, ATP driven pump, light driven pump
coupled trasnport refers to
protein
what is coupled trasnport
two moleqs cross the membrane at some point in time but one moves positively and releases energy
what should you think when you hear pump
energy is required (active transport)
is Na+/K+ ATPase an example of coupled trasnport
no
sodium potassium pump use what type of transport
active
how does sodium potassium pump move
uses 1 ATP to move 3 Na+ out and 2 K+ in
what does sodium potassium pump hydrolyze
hydrolyzes ATP to make ADP
watch video on it
ok
what is the sodium potassium pump chiefly responsible for
maintaining the membrane potential of cells (the difference in charge on either side of a cell membrane)
importance of sodium potassium pump and the Na+ gradient
it drives the active transport of many other solutes across the membrane
what does Na+ influx with sodium-potassium pump begin
-an action potential in neurons (how a neuron relays a neural impulse)
-begins muscle contraction by muscle cells
what do you need for influx with sodium-potassium pump
Na+ gradient
what is coupled transport also called
co-transport
what is coupled trasnport
the electrochemical gradient of one molecule drives the transport of another molecule against its concentration gradient
how many molecules cross the membrane with coupled transport
two
describe how the two molecules move with coupled transport
1)one cross by passive transport: releases energy (exergonic process)
2)crosses by active transport: requires energy (endergonic process)
what are two molecules that go into cell via coupled trasnport
glucose and Na+
-diffusion of Na+ (passive transport) provides energy to pump glucose against its concentration gradient 9active transport)
bulk trasnport
moves larger molecules (polymers) in and out of a cell and depend son membrane fusion and budding
what type of molecules are moved by passive and active transport
small molecukes
exocytosis
large molecules are secreted when a vesicle fuses with the plasma membrane
endocytosis
large molecules are taken in when the plasma membrane pinches inward, forming a vescile
what type of materials are transferred by exocytosis and endocytossi
larger materials acorss cell membrane
where do materials taken up by endocytosis usually end up
lysosome
what are proteins and polysaccharides made by ER and Golgi secreted by
the cell via exocytosis
what is budding and fusion of vesicles critical for
the synthesis and delivery of secreted and membrane proteins
what are three forms of endocytosis
-phagocytosis
-pinocytosis
-repceptor-meditated endocytosis
what is phagocytosis chiefly done by
white blood cells
phagocytosis
cell reaches out extensions that wrap around phagosomes (vacuoles)
do pinocytosis and recepto mediated endocytosis grab anything
no, but it reaches down invaginating and ingested materials get stuck in it.
with what form of endocytosis does cholesterol enter cell
receptor mediated endocytosis
summarize passive trasnport
high -> low [] movement
-does not use []
-moves ions
summarize active tranport
-against [] gradient
-uses energy
-always requires protein
what do passive and active transport both involve
-movement of molecules across/through the membrane
-proteins may be involved
what is [] gradident
diff in [] in 2 areas/2 regions separated by a membrane
are all solutes ions
no
what are ways active transport can obtain energy
-ATP driven pump
-coupled transport
-passive transport
