MCP 25: Solute Transport Flashcards
extrinsic proteins
proteins attached to membrane
intrinsic proteins
proteins embedded in a membrane; may be anchored by cytoskeletal proteins; cannot be removed without destroying membrane
diffusion
the transport of molecules from an area of high concentration to an area of low concentration; water, hydrophobic molecules (nitrogen, oxygen, CO2, benzene) or small nonpolar molecules (H2O, urea, maybe glucose) can passively diffuse through the membrane without ion channels; ions CANNOT move through membrane without channels.
flux
the movement of ions from high to low concentration, measured in amount of particles per time
Fick’s law
Ji=DiA(C1-C2)/x; concentration gradient and flux related linearly
Fick’s law applied to plasma membrane
Jx=Px(Xo-Xi); where Xo and Xi represent concentrations of molecules inside and outside the cell, P is the permeability constant
permeability coefficient for Fick’s law
based on 4 things 1.) partition coefficient 2.) diffusion coefficient 3.) membrane thickness 4.) area over which diffusion occurs
saturation kinetics and solute transport
facilitated diffusion or primary/secondary transport; shows saturation kinetics
active transport
uses energy either directly or indirectly from ATP to move molecules against their concentration gradient
antiport
molecules moving in opposite directions, ATP used indirectly
symport
molecules moving in same direction, ATP used indirectly
V class ATPase
in vesicles, stores chemicals in high concentration
P class ATPase
Na/K pump or Ca2+ transporter
F class ATPase
ATP synthases on inner mitochondrial membrane
Gut epithelial cell glucose transport mechanism
Na+/K+ ATP pump on blood/epithelial cell membrane keeps extracellular Na+ high, intracellular Na+ low. Glucose/Na+ symporter on lumen/epithelial cell membrane allows glucose to enter cell via secondary active transport because of low intracellular Na+ concentration. Glucose moves into blood via facilitated diffusion if concentration gradient permits.
pore (non-gated channel)
leakage channel, allow molecule to move through via simple diffusion, CREATE RESTING MEMBRANE POTENTIAL OF CELL!!!
channel (gated pore)
gated by a door and responsible for action and synaptic potentials
Na+/K+ pump
pumps 3 Na+ out of cell and 2 K+ into cell, against concentration gradients
electrogenic
creates positive charge outside cell and negative charge inside cell (i.e. Na+/K- sodium pump)
types of gated channels
voltage, ligand, mechanical, temperature, and water
p-loop
where the ion binds loosely on a voltage gated ion channel, 5 transmembrane domain on voltage gated ion channels
tetramer channels
Na+, Ca++ and K+ channels–4 subunits (each containing 6 transmembrane helices)
components of a typical ion channel
1.) gate 2.) ion selectivity filter 3.) glycoproteins 4.) anchoring proteins 5.) voltage sensor or ligand binding site
components of voltage-gated channels
6 domains of transmembrane helices, the 5th domains is known as the P loop at is the site for loose ion binding
membrane voltage
charge separation across membrane
partition constant
ratio of a molecule’s solubility in oil to its solubility in water; high number is more lipophilic and results in a great ability to cross hydrophobic core of plasma membrane
carrier mediated transport
primary or secondary active transport
facilitated diffusion
pass transport through pore or channel; technically Vmax exists but concentration of ions in biological systems too high for Vmax to ever be reached; faster that passive transport at low ion concentrations
respiratory pump
H+ ions flow down concentration gradient, releasing energy to drive ATP production
ion channel selectivity
based on size and loose binding for specific ion
pentamer channels
nicotinic ACh receptor channel
hexamer channels
connexons that make up gap junction
