Powerpoint 3 Chapter 13 Flashcards
active transport
pumps use energy to drive unfavorable transport
passive transport
channels allow rapid thermodynamically favorable transport without use of energy
membrane potential formula
dG=RTln(C2/C1) + ZFdV
p-type
forms phospho-enzyme intermediate
Na,K,ATPase transport per ATP
3 Na+ out, 2K+ in
Na+ concentration in and out of cell
14 mM in, 143 mM out
K+ concentration in and out of cell
10 mM out, 100mM in
dG of ATP hydrolysis
-50 kJ /mol
Ca++ ATPase
responisble for maintaining low Ca++ in muscle for relaxation. Located in sarcoplasmic reticulum. High conc in SR, low in cytoplasm.
Ca++ ATPase structure
T domain binds two Ca++. N domain binds ATP. P domain contains Asp that is phosphorylated. A domain links them.
high affinity Ca++binding state of Ca++ ATPase
without ATP bound
inhibitor of Na+,K+,ATPase
foxglove (contains digitoxigenin, a caridotonic steroid)
affect of Na+,K+,ATPase inhibition
increased Na+ in cell. slows down Na+,Ca++ anitporter. Increases Ca++ in heart muscle.
flippases
facilitate membrane lipid asymmetry
type 1 ABS transporters
in prokaryotes. import nutrients
type 2 ABC transporters
in prokaryotes and eukaryotes. function as efflux pumps.
MsbA
an ABC transporter that functions as a lipid exporter
ABS transporter mechanism
open form, no ATP bound. substrate binds, induces conformational change allowing ATP to bind. ATP binds, conformational change allows substrate to other side of membrane. hydrolysis of ATP to reopen
three types of secondary transport
symport, antiport, uniport
uniporter
allows same molecule in or out of cell
lactose permease
symporter that uses a pH gradient to drive uptake of lactose into cell
mechanism of lactose permease
H+ binds from outside. lactose binds from outside. lactose deposited inside. H+deposited inside.
membrane channels
use facilitated diffusion. are gated. have ion specificity
membrane channels gates are turned on or off by (3)
ligands, membrane potential, mechanical means