Proximal tubule- reabsorption

Question 1

Label?

Answer 1

Question 2

Label

Answer 2

Question 3

What epithelial cells present in proximal tubule?

Answer 3

Simple cuboidal

Question 4

What does proximal tubule recieve filtrate from?

Answer 4

Bowmans space

Question 5

What is blood supply of proximal tubule?

Answer 5

Efferent arteriole

Question 6

State function of proximal tubule? (2)
What involved?

Answer 6

1) Reabsorption of: Na, Cl, H2O, Glucose, Amino acids,
HCO3-, Phosphate
2) Secretion organic ions

Question 7

State 3 things reabsorbed at proximal tubule?

Answer 7

Na, HcO3-, Glucose

Question 8

What facilitates reabsorption Na+?
Location?

Answer 8

Na/K ATPase on basolateral membrane

Question 9

How are substrate reabsorbed in proximal tubule? (4)

Answer 9

1) Na+- Na/K ATPase on basolateral membrane
2) Secondary active transport
3) Tight junctions
4) Passive diffusion

Question 10

How is proximal tubule adapted?

Answer 10

1) Lots mitochondria
2) Good vascular supply- Na/K ATPase
3) High permeability H2O- osmosis

Question 11

Where are Cl- ions usually absorbed?

Answer 11

Proximal tubule
Latter

Question 12

Through what channel is water absorbed?
Where?

Answer 12

Aquaporin 1
Apical and basolateral membrane
Osmosis

Question 13

Name two ways water passes through?

Answer 13

1) Aquaporin 1 (AQP1) channels on apical and basolateral
membranes
2) Tight junctions leaky to water- paracellularly

Question 14

How is glucose reabsorbed in proximal tubule?

Answer 14

SGLT1 (carrier protein) 2Na+ and 1 glucose
Latter parts proximal tubule
High affinity for glucose as low concentration

SGLT2 (carrier protein) 1Na+ and 1 glucose
Earlier parts tubule

Question 15

How does glucose cross basolateral membrane?

Answer 15

Passively
GLUT

Question 16

What should glucose content be in urine?

Answer 16

0 (almost)

Question 17

What function SGLT1/2

Answer 17

Reabsorb glucose

Question 18

How is sodium reabsorbed?

Answer 18

1) Na+ actively transported out of proximal CT epithelial cell
Via Na/K ATPase pump (3Na+ out, 2 K+ in) on basolateral membrane
Into the interstitial fluid
2) Lowers conc Na+ intracellularly
3) Na+ move from the tubular lumen into the cell
4) Na+ transported into cell: in exchange for H+ or
co-transported (glucose or phosphate)
5) Once in cell pumped into the interstitium with Na/K ATPase or co-
transported with HCO3-
6) Water follows Na+ passively through osmosis
7) Differences water concentration between lumen and interstitial fluid results in net diffusion of water from lumen across the cell membrane and tight junctions

Question 19

What percentage of Na+ is reabsorbed for protons?

Answer 19

80%

Question 20

What pump used for reabsorption Na?

Answer 20

Na/K ATPase pump

Question 21

What 2 ways N+ moves into cell?

Answer 21

1) Exchange for H+
2) Co-transported e.g. with glucose or phosphate- secondary active transport

Question 22

When in cell how is Na+ pumped into interstitium?

Answer 22

1) Na/K ATPase
2) co-transported with HCO3-

Question 23

What follows Na+?

Answer 23

Water

Question 23

What follows Na+?

Answer 23

Water

Question 24

How is bicarbonate reabsorbed?

Answer 24

1) Tubular secretion of H+ in exchange Na+ 2) H+ combines with HCO3– to produce H2CO3 (carbonic acid) 3) H2CO3 dissociates into H2O and CO2 4) CO2 diffuses through the cell wall as it small and non-polar 5) H2O is reabsorbed through osmosis through AQP1 channels 6) Inside cell H2O and CO2 join together to form H2CO3 7) Dissociates into HCO3– and H+ 8) H+ is recycled through this sequence again 2 methods of HCO3– transport across the basolateral membrane: 1) HCO3- (bicarbonate) is co-transported with Na+ into the interstitium and then into the blood; 1Na+ with 3HCO3- 2) Pumped passively in exchange for an anion

Question 25

What are two methods of transporting HCO3- across basolateral membrane?

Answer 25

1) HCO3- (bicarbonate) is co-transported with Na+ into the interstitium and then into the blood; 1Na+ with 3HCO3- 2) Pumped passively in exchange for an anion

Question 26

What does the combination of HCO3- and H+ form? What does it require?

Answer 26

H2CO3 Carbonc anhydrase

Question 27

What does CO2 and H20 form? What is needed?

Answer 27

H2C03 Carbonic anhydrase

Question 28

Write important equation needed move bicarbonate?

Answer 28

Question 29

How is chloride reabsorbed? How transported on basolateral membrane?

Answer 29

Paracellularly (between cells) Exchanged base on apical membrane (formate) Transported in NKCC2 channel on the basolateral membrane into blood

Question 30

Answer 30

Question 31

What base is exchanged with chloride on apical membrane?

Answer 31

Formate Becomes formic acid- diffuse- reused

Question 32

Give 2 ways amino acids transported? Flow past basolateral membrane?

Answer 32

1) Amino acid transporters 2) Co-transported Na+ Can flow out passively on the basolateral membrane through their own channels

Question 33

Should protein be present in proximal tubule?

Answer 33

No

Question 34

If proteins manages get in what occurs?

Answer 34

1) Microvilli specialised sensors- bind any protein 2) Endocytosis occurs in endosomes 3) Protein degraded by lysosomes to produce amino acids