pumps and ATPases

Question 1

what are the 2 methods of transport across the membrane?

Answer 1

diffusion or active transport

Question 2

types of diffusion

Answer 2

simple and facilitated

Question 3

why do things get transported by facilitated transport?

Answer 3

ionic
hydrophilic
polar
too large

Question 4

active transport

Answer 4

moving against a concentration or electrochemical gradient

Question 5

what is kidney important for?

Answer 5

regulating 
fluid
waste
vitamins
minerals
hormones
electrolytes

Question 6

where is the Na+/K+ pump/ ATPase

Answer 6

every epithelial of the kidney
only on the interstitial side of cell (basolateral membrane)
most cells do

Question 7

what does the Na+/K+ pump do?

Answer 7

3 sodium bind
phosphorylating it
releasing sodium to other side and allows binding of 2 potassiums against the concentration gradient

Question 8

secondary active transport

Answer 8

allowed by the Na+/K+ pump by passive entry, anti-porter and co-transport

Question 9

anti-porter

Answer 9

diffuses sodium into cell and exchanges for H+

no energy used

Question 10

co-tranport

Answer 10

Na+ and another solute diffuse into cell

e.g. glucose simporter

Question 11

nephron can

Answer 11

dissociate the reabsorption of water and sodium

Question 12

where is most sodium reabsorbed?

Answer 12

PCT
50%
nitrogen/ hydrogen exchanger

Question 13

sodium reabsorption in ascending loop of Henle

Answer 13

sodium/ potassium/ chloride transporter

Question 14

water in loop of henle

Answer 14

ascending = water impermeable
descending = water permeable

Question 15

sodium reabsorption in DCT

Answer 15

fine-tuning
by Na+/Cl- transporter
ENaC

Question 16

what happens if K+ levels increase

Answer 16

aldosterone released by RAAS
affects principal cells in collecting duct
causes production of more sodium potassium pumps and ENaCs

Question 17

regulation of transporters

Answer 17

transporters are continuously recycled
transporter synthesis can be up-regulated or
degradation inhibited degradation can be up-regulated
to adjust electrolyte concentrations

Question 18

daily recommendation for K+

Answer 18

3500mg

Question 19

what amount of K+ causes adverse effects?

Answer 19

6000mg, but no upper limit

Question 20

Liddle’s syndrome

Answer 20

gain of function due to impaired degradation of ENaC in collecting duct
pseudohyperaldosteronism
low renin and low aldosterone (only looks like aldosterone is up)
Na+ retention
increased ECF volume and BP
decreased K+

Question 21

how to treat Liddle’s syndrome

Answer 21

low sodium diet

diuretic

Question 22

Gitelman’s syndrome

Answer 22

Na+/Cl- transporter loss of function

Question 23

Bartter’s syndrome

Answer 23

sodium/potassium/ 2 chloride transporter loss of function

Question 24

Pseudohypoaldosteronism

Answer 24

loss of function of ENaC
low sodium
serum osmolality is high because another solute replaces sodium

Question 25

primary polydipsia

Answer 25

drinking in excess causing hyponatraemia | low serum sodium, serum osmolality and urine osmolality

Question 26

what decreases aldosterone

Answer 26

increased water

Question 27

where does reabsorption of water by ADH take place?

Answer 27

collecting duct

Question 28

ADH

Answer 28

increases the permeability of the collecting ducts to water

Question 29

different types of aquaporins are there in the nephron?

Answer 29

1,2,3,4,6,7,8,11 | allows dissociation of water and sodium transport

Question 30

what do aquaporins do?

Answer 30

control osmolality

Question 31

how does ADH increase permeability of the collecting duct?

Answer 31

binds to receptors on interstitial side of epithelial cells GPCR activates adenyl cyclase to convert ATP to cAMP which activates PK A causing vesicle containing AQP2 to move and insert into the membrane on the luminal side

Question 32

AQP3&4

Answer 32

ready in cytosol to be expressed on interstitial side | open channels for reabsorption of water

Question 33

what transporter reabsorbs glucose?

Answer 33

GLUT2 on PCT | facilitated by Na+/K+ pump

Question 34

loop diuretic

Answer 34

blocks NKCC loss of NaCl and K+ reabsorb less K+ so decreases osmotic gradient less water can be reabsorbed due to reduced osmolality in interstitial fluid increases Na+ in collecting duct, so absorbed by ENaC causing more K+ lost changes membrane potential so Ca2+ and Mg2+ lost loss of fluid activates aldosterone via RAAS increasing ENaC activity

Question 35

NKCC

Answer 35

sodium/ potassium/ 2 chloride cotransporter

Question 36

end result of loop diuretics

Answer 36

loss of Na+ and water hypokalemic metabolic acidosis increased Ca2+ loss