solute recovery W1

Question 1

4 parts of the nephron?

Answer 1

renal corpuscle
proximal tubule
Henle’s loop
distal tubule

Question 2

difference between proximal and distal tubules - histology?

Answer 2

proximal tubules have microvilli, distal tubules do not.

Question 3

proximal tubule structure?

Answer 3

lumen (apical side)
microvilli
tight junctions between cells (quite leaky in prox tubule)
basement membrane
basal side

Question 4

things that the nephron epithelia have to recover?

Answer 4

sodium
potassium
calcium
magnesium
chloride
bicarbonate
phosphate
water
amino acids
glucose
proteins

Question 5

what parts in the proximal tubule allow recovery of molecules?

Answer 5

primary active transporters
solute carrier family proteins
aquaporins
ion channels
protein endocytosis receptors

Question 6

common primary active transporters in the proximal tubule plasma membrane?

Answer 6

Na_/K+ ATPase
H+ ATPase

Question 7

solute carrier family proteins - many of these are what? (proximal tubule)

Answer 7

co-transporters powered by established conc gradients (eg in Na+, ‘secondary active transporters’

Question 8

what are aquaporins?

Answer 8

water channels
just let water flow - nothing active

Question 9

sodium potassium ATPase - location and function on cell (proximal tubule)?

Answer 9

located on basal side
active export of Na+ from cell:
2K+ in, 3Na+ out, ATP->ADP+Pi

this creates high sodium in lumen, low sodium in cell. this powers other transport

Question 10

what allows sodium recovery in the proximal tubule?

Answer 10

Na+/H+ exchanger:
Na+ in, H+ out

Question 11

what allows sodium recovery in the distal tubule?

Answer 11

sodium chloride co-transporter:
Cl- in, Na+ in

Question 12

what allows potassium recovery in the loop of Henle?

Answer 12

Na-K-Cl cotransporter:
2Cl- in, Na+ in, K+ in

Question 13

what channels allow potassium out the cell?

Answer 13

ROMK (renal outer medullary K channel)

Question 14

where does amino acid recovery occur?

Answer 14

proximal tubule

Question 15

where does glucose recovery occur?

Answer 15

mostly proximal tubule, partially in loop of Henle

Question 16

what channels allow glucose recovery?

dont have to remember names, remember ratios and molecules.

Answer 16

mostly cotransporter with 1:1 Na+:glucose ratio
also cotransporter with 2:1 Na+:glucose ratio

Question 17

why is diabetes pee sweet!!

Answer 17

uptake systems have limited capacity - fluid flowing through proximal tubule is only there for so long.
too much glucose = total resorbed glucose reaches a threshold, leads to increased excreted glucose.

Question 18

what are anions and cations

Answer 18

anions - negatively charged ions
cations - positively charged ions

Question 19

organic cation transporters function? (OCTS)

Answer 19

allow passive movement in either direction

Question 20

antiporter? for organic cations?

Answer 20

allows H+ in (after being removed by Na+/H+ exchanger), and organic cations are exported out

Question 21

MDR1 pump?

Answer 21

multiple drug resistance 1 pump
active transport of organic cations out the cell

Question 22

organic anion transporter proteins function? (OATPs)

Answer 22

transport larger and somewhat hydrophobic organic anions (including many xenobiotics)

Question 23

examples of anions OATPs transport?

Answer 23

prostaglandins
cholate
ciprofloxacin
cyclic peptides

Question 24

examples of anions OATs transport?

Answer 24

methotrexate
furosemide
penicillin

Question 25

what kind of process is OATs transport? why?

Answer 25

push in, drift out - so entry is active, exit is passive.
gradient of alpha-ketoglutarate across the membrane.
SLC12A3: 3Na+ in, alpha-ketoglutarate in.
OAT1,2,3: alpha-ketoglutarate out, anions in.

Question 26

what can cause toxic levels of anions?

Answer 26

weak drift out - leads to toxic levels of anions in the cell.

Question 27

example of a OAT channel blocker? when is this given?

Answer 27

probenecid
given with anti-tumour therapy to stop kidneys taking up organic anions.

Question 28

why must you take penicillin so often?

Answer 28

lost via OAT channels

Question 29

what allows phosphate recovery in the proximal tubule?

Answer 29

cotransporter allows Na+ in, PO4^2- in

Question 30

bicarbonate equation thingy

Answer 30

bicarbonate + H+ ->/<- carbonic acid.

carbonic acid ->/<- (via carbonic anhydrase) water + carbon dioxide

Question 31

bicarbonate recovery?

Answer 31

CO2 enters cell, meets with H2O and ca to form carbonic acid. this becomes bicarbonate, H+, and the H+ replaces what was lost in the urine. 3 bicarbonate recovered via cotransport with Na+

no net change in pH

Question 32

what happens if there is remaining H+ when the bicarbonate has been taken up? (aka body is in some sort of acidosis)

Answer 32

HPO4^2- picks up H+, becomes H2PO4-, leaves body in urine.
net change in pH as loss of H+

Question 33

how does ammonium leave the body? (when body is short of bicarbonate)

Answer 33

ammonia and H+ form ammonium. this can occur inside or outside the cell.

ammonia comes from broken down glutamine

Question 34

intercalated cells?

Answer 34

type A - throws H+ out the body
type B - throws H+ back into the body

type A throws Away
type B Brings it Back

Question 35

how is calcium recovered

Answer 35

mainly paracellular (between cells - through ‘leaky’ junctions), passive, and driven by osmosis once urine is more concentrated.

Question 36

how does water travel across the kidney cells

Answer 36

aquaporins (mainly aquaporin1)

Question 37

protein uptake in proximal tubule cells?

Answer 37

large proteins such as Megalin. other proteins stick to outside and are brought into cell.