Mangiarua - Tubular Reabsorption

Question 1

Is glucose normally excreted in urine?

Answer 1

No

Question 2

Diffusion between cells

Answer 2

Paracellular

Question 3

Diffusion across the cell

Answer 3

Transcellular (luminal membrane or basolateral membrane)

Question 4

Requires an electrochemical gradient and carriers

Exhibits specificity, saturability, and competition

Downhill transport

Answer 4

Facilitated diffusion

Question 5

The entire overall process of glucose reabsorption depends ultimately on the ________- pump in the basolateral membrane

Answer 5

primary active Na K ATPase

Question 6

Limit to the amount of material the active transport systems in the renal tubule can transport per unit of time

Due to saturation of carriers

Answer 6

Transport Maximum (Tm)

Question 7

Transport max rate of Glucose

Answer 7

375mg/min

Question 8

The appearance of glucose in the urine before the Tm is reached

Answer 8

Splay

Question 9

Reasons for splay

Answer 9

A carrier mediated mechanism shows kinetics similar to those of enzyme systems so that maximal activity is substrate-dependent

Not all nephrons have the same Tm for glucose

Question 10

Describes the mass flows of filtration, reabsorption, and excretion of glucose over the range of plasma glucose concentrations

Answer 10

Glucose titration curve

Question 11

Plasma concentration at which glucose first appears in the urine.

Answer 11

Threshold

Question 12

Renal plasma threshold for glucose?

Answer 12

180-200 mg / 100mL

This will be when glucose is seen in the urine clinically

Question 13

Glucose clearance occurs when ?

Answer 13

Flitered load of glucose is increased

Tubular reabsorptive transport max for glucose is reached

Question 14

Very high levels of plasma glucose ______ all reabsoprtion of xylose

Answer 14

Blocks

Question 15

Affinity of membrane carriers for glucose is ______ than that for xylose

Answer 15

Much higher

Question 16

Renal glycosuria is ?

Answer 16

Glucose in urine as a result of a defective or missing transport mechanism

(Tg = 0 or very low)

Question 17

Are glucose transporters intact in diabetes mellitus?

Answer 17

Yes, glucosuria is due to elevated plasma glucose concentrations, not faulty transporters

Question 18

What can cause glucosuria in pregnancy ?

Answer 18

Increased GFR (glomerular hyperfiltration)

[renal blood flow can increase by 40% due to gestational hormones]

Question 19

Normal clearance of amino acids ?

Answer 19

0

Question 20

Viscous drag

Answer 20

Lining of pore retards forward movement in glomerusu

Question 21

Does normal urine contain protein?

Answer 21

No

Question 22

What three things cause a filtration of proteins to be absent or small

Answer 22

Steric hindrance

Viscous drag

Electrical hindrance

Question 23

How does reabsorption of small linear polypeptides occur?

Answer 23

They are catabolized to AA’s by peptidases in the luminal membrane of the Proximal Tubule and then AA’s are actively reabsorbed

Question 24

Protein bound calcium filters, true or fals?

Answer 24

False

Question 25

What happens to plasma calcium concentration in acidosis ?

Answer 25

More H+ are buffered by plasma proteins, so bound calcium is displaced from proteins and [Ca] increases

Question 26

What happens to [Ca++] in alkalosis ?

Answer 26

The release of H+ from plasma proteins causes the plasma [K++] to decreases

Hypocalcemic tetany possible

Question 27

A ________ of [Ca] causes a release of parathyroid hormone ?

Answer 27

Decrease

This causes increased calcium reabsorption in the kidney and increases [Ca++]ecf

Question 28

High plasma Ca levels ______ PTH

Answer 28

Suppress

Question 29

What protein does calcium bind to in the distal tubule to form a complex that is able to diffuse across the basolateral membrane

Answer 29

Calbindin

Question 30

Water is reabsorbed and everything that is dissolved in the water is reabsorbed with it

Answer 30

Solvent drag

Question 31

___ % of phosphate is actively reabsorbed

Out of the 90% that is filtered

Answer 31

90