Tonicity - comparing 2 solutions | Lab values and concentrations | Heatlh & Medicine | Khan Academy

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Find out how tonicity is determined by ions that don't move across membranes and how it affects the movement of water. Rishi is a pediatric infectious disease physician and works at Khan Academy. Created by Rishi Desai.
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Опубликовано:

23 сен 2012

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Комментарии : 32

@ojwenge 9 лет назад

Brilliant video Question is, when talking about tonicity should one count the molecules that distribute equally between compartment plus those that do not penetrate Or count those that dont penetrate only? arent there isOSMOTIC, hypoTONIC solutions?

@khanacademymedicine 11 лет назад

This will get fixed. Sorry for the confusion.

@cummingspaul_or_cohl2088 2 года назад

I'm concerned that this is still posted with this error.

@Kueytwo 7 лет назад

This video quite helpful, and I liked it. The only thing that bugged me is that the first of the 3 water filled beakers should be 10 solutes on the inside and 8 on the outside of cell. Not 10 and 6.

@ShawnaCostonPhD 7 лет назад

I absolutely love the way you teach. Love it..... Love it.... Love it.

@kg231- 11 лет назад

Well done! Thank you

@cfraser1046 10 лет назад

THANK YOU SO MUCH!!

@Sams-purpose 8 лет назад

Thank you so much! i didn't understand it from my teacher as well as i understood it from you! Really appreciate your time.

@7yaritza 9 лет назад

Completely helped me understand !

@TrevorDHyland 10 лет назад

Doesn't the fact that solute A is permeable to the membrane make this example not work? Wouldn't solute A in the first cup move back out of the cell to form a balance in the amount of solute and thus the cell would not swell? And wouldn't solute A in the last cup move back into the cell to form the balance of solute and thus the cell wouldn't shrink?

@mariagordon-lewis2802 8 лет назад

Thank you for this lesson. Helped greatly for Biology course...

@jenniferpabon717 10 месяцев назад

thank you!

@abdullahmekkawy1315 9 лет назад

amazing and smart explanation thanks alot I realy like your work

@zahraalmousawi4236 10 лет назад

Very helpful video, gonna help me pass my exam. Thank you !!

@hanifmahmud9294 9 лет назад

Isn't there a contradictory thing?First you tell us the actual mediator of tonicity are those that are non permeable solutes but later you explain those three solutions with different tonicity by using just the sums of solutes on either sides, which is basically osmolarity, not stating that which side having more non permeable solutes...would you please be kind enough to clarify that??

@georgehavey 7 лет назад

Yeah I spotted this, the results work out the same, but only by coincidence, when he counts up the molecules he should only count the non-permeable solutes (the yellow and red dots)

@katelynreilly5394 3 года назад

The mediator of tonicity is the solute which doesn't pass through the membrane because the other solutes will distribute evenly either side of the membrane. (you will notice the same number of solute A particles either side of each membrane) So in effect, the other solutes don't affect the tonicity as there will be the same number of particles of either side of the membrane. They themselves will have no impact on the difference of numbers of particles so it doesn't make a difference if you count them or not

@nelsknutson8728 8 лет назад

So in sample 1) of the water and cell. What if it had no solute on the outside instead of the 2 molecules of solute B. would it not burst as it would always be hypotonic?

@mhjjafri 11 лет назад

Hi! Great video - cleared things up really nicely. Just one question: can the terms hypertonic and hypotonic be used to describe the cell as well? I know we use these terms for the solution; but what about the cell? Is a cell in a hypotonic solution called a hypertonic cell? And is a cell in a hypertonic solution called a hypotonic cell? Or are these terms just used to describe the solution? Thanks!

@mohamedelwahsh9266 8 лет назад

Does amolecule of A solute equals amolcule of B solute in the effect of concentration?

@connieanncarty2645 9 лет назад

Hi there. I am a teacher. What program do you use to film these videos? Thank you Connie

@jjguitar22 10 лет назад

I have a point of contention about claims that only Non permeable solutes affect tonicity. I think of tonicity as an extension of osmolarity. Basically, sometimes the fact that there are permeable solutes does affect the volume change of a cell. For example, we have a red blood cell of 300 milliosmoles of sucrose (which is impermeable to the membrane). If we place this cell into a solution of 300 milliosmoles of sucrose plus 50 milliosmoles urea, then urea crosses the membrane. If urea crosses, then water will follow and cause the cell to swell. So it is essentially the concentration difference of the permeable solute that is causing tonicity change. You said permeable solutes do not affect tonicity? Please correct me if I am wrong, I am a TA and would like to know if telling students this is incorrect.

@gilllie666 10 лет назад

why don't salutes with a greater mass have a greater pull on water?

@justdoit2521 6 лет назад

You see, counting the molecules that distribute equally across the whole thing is the same as not counting them. They don't really matter. If you have 10 molecules inside of the cell, and 15 outside of it, and say, 8 of these molecules distribute equally, that means you could substitute 8 from both sides, and you will end up with 2 molecules on the inside, and 7 on the outside, which doesn't really make the tonicity any different than before.

@bombommo 6 лет назад

Second part of the video: does it make all 3 solutions hypertonic if only solute B is accountable for the solution tonicity?

@JaLLaM86 3 года назад

How come it is possible that the solutes do not affect each other, when they clearly affect the water molecules?!! I would think that if molecule 1 which cannot pass between compartments overcrowded compartment A, and molecule 2 which is able to pass between compartments was equally distributed between compartment A and B, then molecule 1 would push some of molecule 2 into compartment A... No?!