Physio 4

Question 1

What does the reabsorption of a substance depend on?

Answer 1

specific membrane transport proteins

Question 2

IS Glomerular filtration specific?

Answer 2

No

Question 3

Is reabsorption of a substance-specific?

Answer 3

Yes

Question 4

What is the reabsorption rate in the proximal tubule?

Answer 4

80 ml/min

Question 5

Is there a change in the osmolarity of the fluid as it passes through the proximal tubule?

Answer 5

No

Question 6

What is the osmolarity of the fluid as it enters the loop of henle?

Answer 6

300 ml (almost same)

Question 7

Which substances are absorbed in the proximal tubule?

Answer 7

Sugars
Amino acids
Phosphate
Sulphate
Lactate

Question 8

Which substances are secreted into the proximal tubule?

Answer 8

H+
Hippurates
Neurotransmitters 
Bile pigments
Uric acid
Drugs (atropine, morphine, penicillin)
Toxins

Question 9

How is adrenaline and noradrenaline excreted?

Answer 9

Via the urine

Question 10

What are the barriers which the substance must cross to get undergo transcellular tubular reabsorption?

Answer 10

1. Luminal membrane of the epithelial membrane
2. Cytoplasm
3. Basolateral membrane
4. Interstitial fluid space

Peritubular capillary

Question 11

What

Answer 11

tight junctions at the apical junctions

Question 12

What is the route of paracellular reabsorption?

Answer 12

Varies btw different segments of the nephron

some areas tighter and some areas of the nephron less thick - determines the reabsorption

Question 13

What does transcellular reabsorption depend on?

Answer 13

Transport protein

one at the apical membrane and the other at the basolateral membrane

Question 14

What are the primary active transporters?

Answer 14

Need energy from the hydrolysis of ATP to move something against the concentration gradient.

eg: Na/ K pump - pumps 3 Na out and brings 1 K in for each ATP molecule

Question 15

What is the secondary active transport?

Answer 15

The carrier molecule is transported coupled to the down concentration gradient of an ion (usually Na+)

moves something either in the same(symporters) or opposite direction(antiporters)

Question 16

What is facilitated diffusion?

Answer 16

Passive carrier-mediated transport of a substance down its concentration gradient

eg: moves glucose across the lipid bylayer via the protein, no energy

Question 17

Where are the Na/K pumps present?

Answer 17

only at the basolateral membrane

Question 18

What is the main function of the Na/ K pump?

Answer 18

To maintain the concentration gradient of Na across the cell membrane

Question 19

Is the proximal tubule membrane leaky or not?

Answer 19

Yes it is

Question 20

What are the transport proteins present in the apical membrane of the proximal tubule?

Answer 20

Na/ Glucose symporters

Na/ Amino symporters

Na/ H anteporters

Question 21

What is the net movement of the Na in the proximal tubule?

Answer 21

From the filtrate to the peritubular capillaries = transcellular movement

Net reabsorption of the positively charged Na via this them

Question 22

What is the net movement of the Cl in the proximal tubule?

Answer 22

sets up an electrical gradient and coupled to the reabsorptio nof Na, Reabsorption via the
paracellular route occurs for Cl

Question 23

How does the osmolarity of the fluid change in the proximal tubule?

Answer 23

No change. Reabsorption of salt and water both occur in the proximal tubule hence the osmolarity remains the same

Question 24

What is the net movement of the Cl in the proximal tubule?

Answer 24

Due to the osmotic drag of the NaCl and moves across from the tubule to the peritubular capillaries

Question 25

What is the oncotic drag of the peritubular capillaries?

Answer 25

plasma protetins in the peritubular capillaries pulls the slat and water from the lateral space into the peritubular capillaries

Question 26

How is glucose reabsorbed in the proximal tubule?

Answer 26

Via Na/ glucose symporters concentration gradient across the basolateral membrane and it uses a facilitated transporter to move the glucose from inside the cell into the interstitial fluid moved across the tubular cell via the transcellular route water follows the glucose gradient via paracellular route and into the peritubular capillaries.

Question 27

Which route does water take to cross the eipthelial cell in proximal tubule?

Answer 27

Paracellular route

Question 28

How does glucose reabsorption in the proximal tubule change the osmolarity?

Answer 28

No change remains the same as the water is also absorbed with it

Question 29

What force causes the movement of glucose and water across the membrane?

Answer 29

oncotic drag of the peritubular capillaries

Question 30

What is the transport maximum (Tm)

Answer 30

max rate at which a substance can be reabsorbed by the kidney dependent on the specifc membrane transport protein

Question 31

Rate of filtration

Answer 31

Plasma concentration of A x GFR

Question 32

What is the plasma concentration of the glucose?

Answer 32

4-5 mmol/ L

Question 33

What happens if the plasma concetration of the glucose is > 10-12 mmol/L?

Answer 33

10-12 mmol/L the transport mechanisms that reabsorb glucose is saturated

Question 34

what happens if we filter lots of glucose?

Answer 34

lots og flucose in the tubular fluid, only can move a certain amount via the transporters and the rest gets peed out

Question 35

What is the platea line in transport maximum?

Answer 35

kidney filtering higher than normal plasma glucose concetration - uncontrolled diabetes

Question 36

What marker is used for finding the plasma renal flow?

Answer 36

Para-amino hippuric acid

Question 37

What does the secretion of H+ depend on?

Answer 37

Membrane transport protein

Question 38

Comment on the transporters in the proximal tubule with respect to saturation.

Answer 38

transport protein thats secrete and reabsorb substances can both be saturated

Question 39

What is the osmotic concentration of the tubular fluid when it leaves the proximal tubule?

Answer 39

iso-osmotic - 300 mosmol/l