Epithelial Transport Flashcards
At rest, the apical _____ channels are closed.
Cl-
What kinds of metabolic waste molecules are non-volatile?
urea and protons
_____ cannot maintain large energy gradients because solutes and water leak back across the epithelium through the pericellular shunt.
Leaky epithelia
In the lungs, ____ diffuses passively from blood to air.
CO2
How does someone get cystic fibrosis?
it’s genetic
How do the kidneys filter waste?
the epithelial cells lining the tubules reabsorb the things that it wants to keep (glucose, salts, bicarbonate, etc)
Each day the cells in an adult human produce about ____ of metabolic waste solute.
15 moles
What is Uremia?
urine in the blood
Functions of the kidney include excreting non-volatile metabolic wastes and _____.
regulating the composition of virtually all ECF solutes as well as water
By keeping the ______ concentration low, the Na/K pump provides the energy to drive a host of secondary transporters.
intracellular sodium ion
How are the metabolic waste solutes removed from the body?
fluid exits the lungs; the kidneys do the rest
Synonyms for _____ include serosal and peritubular.
basolateral
Where are water pumps located in the body?
they don’t exist
What is the defect in cystic fibrosis?
the Cl- channel is mutated, reducing the epi’s ability to secrete serous fluid, causing very thick mucous and infections
What does CFTR stand for?
Cystic Fibrosis Transmembrane Conductance Regulator
In general, epithelia engaged in _____ are leaky, while those epithelia doing the finishing work are tight.
massive transport of substances
A ____ transepithelial voltage would be measured in leaky tight junctions.
lower
By keeping the intracellular sodium ion concentration ____, the Na/K pump provides the energy to drive a host of secondary transporters.
low
In general, epithelia engaged in massive transport of substances are leaky, while those epithelia _____ are tight.
doing the finishing work
How are the GI tract epithelium transporters regulated?
they aren’t- they will absorb everything ingested
Water always moves passively down _____.
osmotic gradients
What is the equation for transepithelial potential difference (transPD)?
TransPD = Vm (Basolateral) – Vm (Apical)
How does cholera toxin work?
it locks open the Cl- channels, causing a massive efflux of fluid from the cell
Water always moves _____ down osmotic gradients.
passively
The _____ is always located on the basolateral membrane.
Na/K pump
Synonyms for _____ include mucosal and luminal.
apical
What is the key player in secretion of fluid by an epithelial cell?
the Cl- channel
The ____ and _____ are examples of sodium-dependent secondary active transport systems.
sugar; amino acid pumps
The sugar and amino acid pumps are examples of ______.
sodium-dependent secondary active transport systems
Functions of the ____ include excreting non-volatile metabolic wastes and regulating the composition of virtually all ECF solutes as well as water.
kidney
The driving force for nearly all transport is the ______.
Na/K pump
Leaky epithelia cannot maintain large energy gradients because solutes and water leak back across the epithelium through the _________.
pericellular shunt
Name 2 ways a substance can cross the epithelium.
1) entering the epi and exiting the other side 2) pass through the tight junctions via the pericellular shunt pathway
Synonyms for basolateral include _____ and ______.
serosal; peritubular
A lower transepithelial voltage would be measured in ____.
leaky tight junctions
____ always moves passively down osmotic gradients.
Water
Epithelial cells transport glucose by ____.
sodium-dependent secondary active transport pumps
____ are the main exception to the otherwise universal dependence of epithelial pumping on the Na/K pump.
Protons
The Na/K pump is always located on the ______.
basolateral membrane
Functions of the kidney include_____ and regulating the composition of virtually all ECF solutes as well as water.
excreting non-volatile metabolic wastes
How does Cl- leaking into the lumen pull water with it?
Na+ passively follows Cl-,and the resulting osmotic gradient draws water along with it
What is the pericellular shunt pathway?
solutes and water passing in between the epi cells through leaky tight junctions
By keeping the intracellular sodium ion concentration low, the _____ provides the energy to drive a host of secondary transporters.
Na/K pump
What activates the Cl- channels?
hormones, parasympathetic nerves, pathogens
Synonyms for apical include _____ and ______.
mucosal; luminal
vasopressin
anti-diuretic hormone
How is a sugary snack absorbed by the epithelium?
NaCl leaks from the blood and crosses the leaky tight junctions
Each day the cells in an adult human produce about 15 moles of _____.
metabolic waste solute
At rest, the apical Cl- channels are _____.
closed
Non-epithelial cells transport glucose by _____.
facilitated diffusion
Protons are the main exception to the otherwise universal dependence of epithelial pumping on the ____.
Na/K pump
