# Question in Physiology ?

Discussion in 'Medical Students - MD' started by ssstrong, Jun 20, 2008.

1. ### ssstrong

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Hi

Sorry if I post in the wrong Section ...

if red blood cells were placed in 5.5% NaCl Solution, what would be the effect on the cells? What if they were placed in 5.5% glucose Solution ?

BEST REGARDS

Saman SarKO

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3. ### Blade28

5.5% NaCl solution? Wow that's concentrated! Normal saline is only 0.9%.

Are you asking about the effects of hypertonic solutions on cells?

4. ### ssstrong

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Hello

yes what happened to the RBC if i placed it in Nacl 5.5% , and another RBC placed in 5.5% Glucose (Compare the Two )

Thnx

5. ### DickyV

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Well, 5.5% saline is certainly hypertonic relative to the inside of an RBC. So now think - will water flow towards or away from the higher concentration? Then figure out what happens to the size of the cell (shrink/swell/same).

For glucose, you're going to do the same thing, but you have to first calculate the concentration of glucose given a 5.5% solution of glucose (hopefully you remember this from GenChem). Basically - you have 5.5g glucose per 100mL H2O (assuming vol. %). Calculate that out to molarity, and compare to the standard molarity of 300 mOsm/L. (Technically osmolality, but most physiologists, unfortunately, treat them as the same.)

If you need more help, let me know.

6. ### ssstrong

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Thnx Dude ...

In 5.5% NaCl , Because it it hypertonic so the fluid will move from the RBC to the Surronding Solution so the RBC will SHRINK...

Here i have Question :

I know that 0.95% NACL is isotonic .

is any number above or below this concetration will cause either shrinkage or swelling respectivlly ???

About Glucose Solution Could you help me more if you can ??

Thank you AGAIN ...

7. ### The Angriest Bird

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I believe the trick is that NaCl gives you TWO particles (Na+ and Cl-) while glucose gives you only ONE particle. So at same concentration, NaCl solution should have double the osmolarity of glucose solution.

Therefore the answer is probably something like "the RBC will shrink more in NaCl solution as opposed to glucose solution."

8. ### DickyV

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Correct.

Also correct.

What Yeast said is probably the point - that salt contains two osmoles while glucose is non-ionizable and, therefore, contains only one.

If you need a quantitative answer, then you would figure out the osmolarity of 5.5% glucose versus 5.5% NaCl and compare that against a reference chart. Some back of the envelope calculations may be easier, though.

NS is 0.9% NaCl and has an osmolarity of 300 mOsm/L (approximately). 5.5% NaCl is about 6 times more concentrated than NS, so we would expect the osmolality to be _____.

Now, since we know that NaCl has two osmoles while C6H12O6 has one, we know that, at the same % concentration, glucose will have _______ the osmolarity of NaCl.

9. ### ssstrong

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Hello ...

in the First blank 6 X 300 = 1800 mOsm/L . RIGHT ??? so as we said SHRINKAGE

Second Blank, as it has the half osmoles it will 1800 / 2 = 900 mOsm/L . RIGHT ? Then here also will Shrink ???

Now I the Conc. of Glucose be 0.92% What Happen ? Hypotonic ?

Thank you

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10. ### Leiflet Outward Bound Has-Been

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If your answer can be qualitative, the glucose causes no change. 5.5% SOUNDS LIKE A LOT BUT REMEMBER MW . The 5.5% NaCl is obviously very hypertonic.

If you need numbers...

55g/180(g/mole)=0.3M glucose (300mOsm)

55g/58(g/mole)=0.9M NaCl (1800mOsm)
Let me know if I made a bonehead move there but I'm willing to bet that most of us have has D5W and we're still here. A bag of that salt would probably kill you.

Oh, and 0.92% Glucose would lyse the cells 0.92% NaCl would cause imperceptible shrinkage.

11. ### DickyV

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I have to apologize - I totally forgot to account for the different MWs of glucose and salt. (Summer vacation has shut off my brain.)

12. ### gro2001 SOCMOB Physician Faculty

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Also, the cell membrane is permeable to glucose, so glucose will only cause a transient change in the size of the cell. Only impermeable molecules cause permanent changes.

13. ### The Angriest Bird

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Good point but I think you are making the problem too complicated. RBC membrane is also permeable to Na and Cl ions, but through carriers/transporters. Na/K ATPase for example. It's a physiology question. There's no need to get neuroscience involved

14. ### gro2001 SOCMOB Physician Faculty

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OK, I dont mean to be anal about this, but Na/K ATPase does not make the membrane permeable to these ions since they are each going only one way (sodium out, potassium in) and an equilibrium is established. Also, all the ion channels I can think of are open only under special circumstances (ligand binding to receptor say).

But yeah, maybe thats over thinking it.

15. ### ssstrong

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Hello

Thank you to all My Freind ....

Is this answer correct :

1-in 5.5% NaCl Solution the RBCs will Shrink because the sol. is hypertonic.

2-in 5.5% Glucose nothing happen because the solution is isotonic.

3-in 0.92% Glucose the RBC will swell because the sol. is hypotonic.

4-in 0.92% Nacl is RBC will Shrink small or we can say nothing happen because
the sol. is samll hypertonic

5-The 0.9% NaCl is the Conc. when the sol. is ISOTONIC.

6-The 5.5% Glucose is the Conc. when the sol. is isotonic .

Best Regards

Saman SarKO

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17. ### Leiflet Outward Bound Has-Been

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Fix your spelling and usage and you're set. (#4 is not really worth mentioning)

18. ### absolutjag9

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Classify the following solutions (according with the osmolarity and tonicity) Indicate how the body fluid compartment and osmolarity will change when 1 Liter of the following solutions is administered IV. (increase, decrease, no change)

i need a little help here...whats diff btwn osmolarity and tonicity?

a. 300 mM NaCl

b. 1.8% saline solution

c. 0.45% NaCl + 5% dextrose in water (D5W)

can anyone help me on this one? i have some answers but need a little guidance- for A i am going to multiply 300 mM NaCl by 2 mOsm Nacl since it dissociates into Na+ and Cl-. Then I will divide this by 1L to get osmolarity. so 600 mOsM NaCl/1L of NaCl= 600 mOsm. Normal cell mOsm is 300 so this would be hyperosmotic. for tonicity it would be hypertonic also.

for b, i need help converting saline into mOsm/L can anyone help

same for c

any help would be appreciated

19. ### absolutjag9

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update: i calculated 1.8% saline to be the following:

1.8 g NaCl/0.100 L of H2O / 58.443 g/mol NaCl x 2 x 1000 = 615.984 mOsm/L

what i am confused about is the osmolarity versus tonicity. nacl will go into the cell but be transported out as they are primarily extracellular ions. as compared with the cell's 300 mOsm/L environment, i would think this saline concentration is going to be hyperosmotic and hypertonic with respect to the cell.

for b, hypertonic saline is added to the extracellular space, the initial concentration of solute outside the cells will begreater than that inside the cells. This will drive water out of the cells, toward the higher NaCl concentration, until the concentration is the same inside and outside the cells. so hyperosmotic would still apply correct?

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20. ### Slow

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lalala

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