Transport Of Amino Acids, Glucose, Urea, Sulphate

Question 1

Where is all of the filtered glucose reabsorbed?

Via what method?

(0.2 to 0.5mM filtered per minute)

Answer 1

• PCT

- By Secondary Active Transport, using energy from Na+ transport down its conc. gradient

Question 2

Why is Glucose reabsorption limited?

Answer 2

There is a limited number of Na/ Glucose carriers, through which Na and Glucose are symported into blood

Question 3

Beyond what plasma glucose concentration do we get Glycosuria

Answer 3

10mM (as in Diabetes)

Question 4

How can we look for Glycosuria?

Answer 4

Using a urine dipstick

Question 5

What is the plasma concentration of amino acids?

Answer 5

2.5 to 3.5 mM

Question 6

Where are amino acids reabsorbed?

By what mechanism?

Answer 6

• PCT
• Secondary Active Transport, symported with Na+ (as with glucose)

(There are at least 5 different transport systems coupled with aa reabsorption)

Question 7

Is Amino acid reabsorption limited?

Answer 7

Yes (there is a maximal reabsorption rate)

Question 8

The Urea concentration increases as it travels along nephron, because Na+, Cl-and H20 are reabsorbed.

What is the significance of this increase in concentration?

Answer 8

This allows passive reabsorption of 40-50% of the urea

Urea diffuses across, no transport mechanisms in place

Question 9

Which 2 parts of the nephron are impermeable to urea?

Answer 9

• DCT

- CD