L17 Gene Models And Nephron Function 1

Question 1

What is the first step of the production of urine?

Answer 1

Glomerular filtration. Blood enters the glomerulus and is filtered through a specialised membrane.

Water and small solutes like glucose, amino acids and waste products pass through the membrane and into the Bowman’s capsule

Question 2

List the parts of nephron, in the correct order

Answer 2

1. Glomerulus
2. PCT - Proximal convoluted tubule.
3. loop of henle
4. Distal convoluted tubule
5. Collecting duct.

Question 3

What is the standard glomerular filtration rate (GFR)?

Answer 3

125 ml/min

Question 4

What is in the renal tubule?

Answer 4

Proximal tubule, loop of henle, distal tubule and collecting duct

Question 5

What’s the difference between paracellular and transcellular secretion/ reabsorption?

Answer 5

Paracellular secretion happens in between the cells and not across the cells like transcellullar

Question 6

What’s the direction of transcellular secretion in the proximal tubule for reabsorption?

Answer 6

Direction of transcellular transport is from the tubular lumen (apical side) to the interstitial fluid (basolateral side)

Opposite direction of secretion

Question 7

Describe the handling of phosphate in the proximal tubule

Answer 7

Phosphate is co-transported with sodium ions across the apical membrane into the membrane

Sodium phosphate cotransporter (NaPilla) located on apical membrane

Question 8

What is the main role of the proximal tubule?

Answer 8

Main role of the proximal tubule is to reabsorb essential substances from the filtrate back into the bloodstream

Glucose, amino acids and sodium ions are reabsorbed

Question 9

How is there a sodium concentration gradient established within the proximal tubule?

Answer 9

1) Sodium/potassium pump located on the basolateral membrane of the proximal tubule cells actively transports 3 sodium ions into the interstitial fluid, out of the cell
2) Sodium ions are then co transported with substances like glucose, amino acids and phosphate down the sodium concentration gradient

Question 10

Why is it important that sodium ions are actively transported out of the proximal tubule?

Answer 10

1) Maintains a sodium gradient
2) Sodium gradient powers the secondary active transport of other essential substances like glucose, amino acids, and water

Question 11

What are the impacts of NaPilla knockdown?

Answer 11

Decreased phosphate reabsorption from the tubular fluid back into the bloodstream so increased phosphate excretion in the urine and decreased phoshphate level in the blood

Question 12

Describe the handling of bicarbonate by the proximal tubule

Answer 12

1) Sodium- hydrogen exchangers (NHE3) on the apical membrane actively transports H+ into tubular lumen for Na+ into cell
2) Secreted H+ combine with filtered biocarbonate ions (HCO3-) in lumen to form carbonic acid (H2CO3)
3) Carbonic anhydrase, an enzyme, catalyses the conversion of H2CO3 into CO2 and H2O
4) CO2 and H20 diffuses across the apical membrane and is converted back into H2C03 by the same enzyme which then dissociates into H+ and HCO3-

Question 13

What does NHE3 do?

Answer 13

Sodium- hydrogen exchanger 3.

Reabsorbs Na+ and secretes H+ in proximal tubule