w6 membrane transport Flashcards
what are 3 types of extracellular fluid
blood plasma, interstitial fluid, transcellular fluid
what is hematocrit
the fraction of blood volume that is occupied by RBC
how is hematocrit determined
centrifuging blood that is treated w anticoagulant and measuring fraction of total volume that is occupied by packed RBC
what separates the intravascule and interstitial compartments
walls of capillaries
where is interstitial fluid found
outside the intravasculr compartment
what does transcellular fluid count as
includes synovial fluid within joints, cerebrospinal fluid surrounding brain and spinal cord, fluid trapped within spaces that are completely surrounded by epithelial cells
does transcellular fluid include fluids that are outside the body
no (gastrointestinal tract or urinary bladder doesnt count)
intracellular fluid K+, Na+, Cl- levels low or high
high in K+, low in Na+ and Cl-
extra cellular fluids (interstitial and plasma) K+, Na+, and Cl- levels
high in Na+ and Cl-, low in K+
what direction is Na-K pump which goes in and out (and how many for each)
3 Na+ is leaving the cell to actively transport 2 K+ into the cell
what is simple diffusion driven by
thermal motion of molecules
(proportional to concentration difference)
osmosis
higher water [ ] to lower water [ ]
impermeable to solutes
pores are
conduits that are always open
channels are
conduits that are gated by a door
carriers
conduits that never offers continuous transmembrane path bc it is equipped w at least 2 gates that are never opened at the same time
primary active transport
directly coupled to the hydrolysis of ATP
Na+/K+ alpha and beta subunit functions
alpha - mediates active transport
beta - essential for proper assembly of the pump
does Na+/K+ pump use energy
yes
E1 and E2 conformational states for Na+/K+ pump
E1 - binding sites for ions face the inside of the cell
E2 - binding sites face the outside
model of action for Na+/K+ pump (which goes in or out first)
Na+ goes out first than K+ goes in
what can block Na+/K+ pump
cardiac glycosides such as ouabin and digoxin (compete w K+ for binding)
hypokalemia is low blood Na+ or K+
low blood K+
what is the inside negative membrane voltage
~60mV
H-K pump (HKA) is found where
parietal cells of the gastric gland
HKA extrudes H+ where
extrudes H+ across the apical membrane into the gland lumen
Ratio of HKA pump for K+,H+, ATP
uptake 2 K+, extrude 2H+, uses 1 ATP
where are Ca2+ pumps found
plasma membrane of plasma membrane Ca2+-ATPase (PMCA cells)
SR and ER (play role in active sequestration of Ca2_ into intracellular stores)
ratio and direction for ca2+ pump for H+,Ca2+, ATP
1 H+ for 1 Ca2+ for each hydrolyzed ATP
Ca2+ goes out, H+ goes in
sarcoplasmic and endoplasmic reticulum calcium ATPase (SERCA) ratio
2 H+ and 2 Ca2+ for each ATP hydrolyzed
H+ goes out, Ca2+ goes in
where are vaculolar-type (v-type H+ pump) found
intracellular organelles such as lysosomes, endosomes, secretory vesicles, storage vesicles, golgi apparatus
V-type H+ pump pumps H+ what direction
from cytoplasm to interior of organelle (in)
multidrug resistance transporters (MDRs)
MDR1 pumps what
pumps a wide range of anticancer drugs out of cancer cells, rendering cells resistant to these drugs
secondary active transport
against the electrochemical gradient using energy in electrochemical gradient of other molecules to drive this transport
3Na+-Ca2+ antiporter direction
secondary active transport of Ca2+
3Na+ in, 1Ca2+ out
2 major classes of secondary active transporters
cotransporters (symporters)
exchangers (antiporters)
cotransporters (symporter)
driving and driven solutes moving in SAME direction
generally driven by energy of inwardly directed Na+ garident
cotransporter (symporter) example
sodium glucose linked transporter (SGLT)
sodium amino acid transporter
exchanger (antiporter)
driving and driven solutes more in the OPPOSITE direction
(generally exchange + for + or - for -)
example of exchangers/antiporter
sodium-calcium exchanger
Na-Ca exchanger ratio and direction
3 Na+ per 2 Ca2+
moves net positive charge in same direction of Na+
inwardly directed Na+ drives Ca2+out of cell
hypertonic vs hypotonic
hypertonic - water moving out of cell
hypotonic - water moving into cell
isosmolal osmolality level
hyperosmolal
hypoosmolal
290 mOsm
hyper >
hypo <
colloid osmotic pressure/oncotic pressure difference tends to pull water from what to what
from interstitium to plasma
hydrostatic pressure difference across capillary wall drives fluid from where to where
from plasma to interstitium
ultrafiltration
when hydrostatic pressure exceeds the colloid osmotic pressure and there is movement of water out of capillary
