Mineral ions and the ascending limb??

Hey! I just wanted to check some details on the function of the kidney, my textbook says that Na+ diffuses into the descending limb of the loop of Henle causing the concentration of the tubule fluid to rise. However, my teacher stated that the descending limb is impermeable to mineral ions and permeable to water so there would be no movement of mineral ions. The internet says the descending limb has a low permeability to ions. The question is do mineral ions move into the descending limb or not? (I believe they do not as they diffuse down a steep concentration gradient at the beginning of the ascending limb then further up are actively transported into the tissue fluid of the medulla. Some confirmation would be appreciation, thank you! 😊💖

Reply 1

Kim J

13

Firstly, this is what is mentioned in my biology course book:
The descending limb is permeable to water
The ascending limb is not.
Both limbs contain ions

Now, I will explain in a brief way that I found (from a summary in my book)

Na and Cl ions are actively pumped out of the Ascending Limb
Tissue fluid concentration is Raised
This causes water loss from the Descending Limb (down the water potential gradient)
Descending Limb is now more concentrated with Na and Cl ions (since the water has moved out)
Na and Cl ions diffuse out of this concentrated solution
This happens in the lower part of the Ascending Limb ( because solution has moved down from descending and is about to go into ascending limb)

If you have the GREEN CIE AS AND A LEVEL BIOLOGY coursebook EDITION 4 (Mary Jones and co) , go to page 311 and have a look at the diagram.
It may be available on PDFdrive as a pdf

Reply 2

EDeHavas

OP

11

Original post by Kim J

Firstly, this is what is mentioned in my biology course book:
The descending limb is permeable to water
The ascending limb is not.
Both limbs contain ions

Now, I will explain in a brief way that I found (from a summary in my book)

Na and Cl ions are actively pumped out of the Ascending Limb
Tissue fluid concentration is Raised
This causes water loss from the Descending Limb (down the water potential gradient)
Descending Limb is now more concentrated with Na and Cl ions (since the water has moved out)
Na and Cl ions diffuse out of this concentrated solution
This happens in the lower part of the Ascending Limb ( because solution has moved down from descending and is about to go into ascending limb)

If you have the GREEN CIE AS AND A LEVEL BIOLOGY coursebook EDITION 4 (Mary Jones and co) , go to page 311 and have a look at the diagram.
It may be available on PDFdrive as a pdf