Biology

Can anyone help me - I have to write a practical report (although I have done some before ) that I can't get my head around. In class, 1 student drank 1 litre of water and another drank 1 litre of isotonic fluid - they both then measured how much urine they passed over the next 2 hours. They both passed same amount .........I can't get my head around the hypothesis and the result ?? Can anyone help me please ?

Reply 1

dogtanian

16

GCSE, AS or A level...?

Reply 2

beverleycob

OP

It's actually HEFC which is equivelant to A level

Reply 3

dogtanian

16

Hmm. Well, I'll move it to the academic forum anyway.

You'll get a better response there, from people that knows their biology.

And I just realised that I didn't actually have to ask what level you were studying at to know what forum to move it to.

Reply 4

Comp_Genius

4

I would have thought that the person who drank pure water would urinate a higher volume than the person who consumed isotonic saline.

Reply 5

beverleycob

OP

Thanks for ur reply
presumably this is because of the osmotic pressure being the same in the cells as in the isotonic fluid? therefore the hypothesis would be exactly that - even though the hypothesis was not supported - Yes?

Reply 6

Comp_Genius

4

maybe student 1 (who drank pure water) had a high salt meal before?

Reply 7

Revenged

15

beverleycob

Thanks for ur reply
presumably this is because of the osmotic pressure being the same in the cells as in the isotonic fluid? therefore the hypothesis would be exactly that - even though the hypothesis was not supported - Yes?

Water uptake at the small intestine (where most water is absorbed) occurs by Na+ and glucose uptake causing the uptake of water

If you used sodium or glucose as part of the isotonic solution then you should have increased, and not decreased, water uptake...

This is why oral rehydration therapies use have a high sodium / glucose intake as it is more easily absorbed than pure water.

To the question of why there is no difference... it's something to do with the kidney... loop of Henle perhaps - though I haven't done this since A-level so i dunno

(and i'm not even the one supposed to be revising physiology :wink:

)

Biology

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