Cellular Transport

Question 1

CFTR malfunction

Answer 1

unable to be exported to the surface membrane

Question 2

CF presentation

Answer 2

salty/limited sweating
disrupted pancreatic function /w loss of enzyme secretion
airway dysfunction with greatly increased infection susceptibility

Question 3

CF gene

Answer 3

7th chomosome

Question 4

CFTR function and mutation mech

Answer 4

ABC cassette channel, binds ATP to open; common mutation is in this region causes inability to function properly; also has a regulatory domain on the intracellular side that must be +p to function

Question 5

MDR

Answer 5

allows hydrophobic substances to be exported from cells; this often moves chemotherapy out of cells

Question 6

tight junctions

Answer 6

allow the passage of h2o and small cations, but not proteins and anions; there are exceptions though

Question 7

basolateral=

Answer 7

interstitial

Question 8

Na/K pumps are located at the (basal/apical)

Answer 8

basolateral membrane

Question 9

most physiological secretions are at what tonicity?

Answer 9

hypotonic - secreted hypertonic, water joins, salt reabsorbed to make them hypotonic

Question 10

sweat tubule cells establish their high Cl concentration with this channel:

Answer 10

Na/K/Cl symporter

Question 11

Sodium is moved into the tubule when…

Answer 11

Cl is exported out of the apical side of the tubule and Na is attracted through the gap junctions between epithelial cells

Question 12

Cl channels on the apical membrane of the sweat tubule are activated by….

Answer 12

calcium

Question 13

tight junctions in the ducts of sweat glands maintain sodium because they are…

Answer 13

impermeable to ions

Question 14

in the sweat duct intracellular Cl levels are low because…

Answer 14

CFTR channels pump them out

Question 15

sodium channels on the apical side of the sweat duct are called

Answer 15

ENaC (epithelial sodium channels)

Question 16

why is CFTR so common?

Answer 16

in diarrhea, such as that caused by vibrio cholera, the CFTR channel absence will prevent Cl secretion into the lumen, thereby limiting the osmolarity of the waste, and thereby limiting the diarrhea

Question 17

CFTR effect on pancreatic secretions

Answer 17

NaCl is present in the duct, Cl- is reabsorbed and exchanged for bicarb. by the anion exchanger; the anion balance then causes Na to permeate through the tight junctions between the duct’s epithelial lining

Question 18

CFTR and airways

Answer 18

ASF is slightly more acidic in CF patients, perhaps the CFTR plays a role in alkalinizing it, which may enable the lysozymes to do their work of inhibiting bacterial growth