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Ok. So my question which I don't understand..Hypotonic, Hypertonic, and Isotonic. Can you explain those in a basic way?
Yes. If you have a solution - salt dissolved in a cup, for example - you can always consider its concentration. The proportion of salt molecules to the proportion of water molecules. When there are a lot of salt molecules relative to water molecules, the water is very salty. If there are only a few salt molecules relative to water molecules, then the water is a little salty. The key is that the salt molecules have a concentration and that concentration depends on the number of salt molecules and the number of water molecules. That is the one solution case - it's sort of background to the hyper/hyp/isotonic terms. Is that much clear?
Hypotonic means less salt, more water. Hypertonic means more salt, less water. Isotonic means an equal amount of salt and water
@cmp1210, yes it does. But the key is that these terms are always, always used to compare the concentrations in two different solutions. Usually they are separated by a barrier or membrane permeable to one type of molecule or not the other, or are able to exchange molecules in some other way.
A little. I think of Hypertonic as more active/more strength. Isotonic as same. And hypotonic as less active/less strength. More like how I think Isotonic is like the PH 7. And Hypertonic is basic. And Hypotonic is acidic...
Erm. My picture looks more like this: |dw:1355872170675:dw| Imagine the barrier between the two compartments is permeable to water molecules only, not salt. This picture is the moment after salt has been added to one of the compartments. The one on the left is hypertonic to the one on the right, which is hypotonic to the one on the left. They are like ying and yang - these terms can't apply to one thing by itself, they have to relate one thing to another. And after time passes, of course water molecules will diffuse down their concentration gradients (water from the right compartment will move into the left compartment), so then the two solutions on either side will be isotonic.
Yeah..its kinda what I am thinking..
It is quite similar. When a solution has a really high concentration, it is likely that it will be hypertonic when compared to most other solutions. But if you found some other solution with a really, really, really high concentration, then the initial concentration would be hyptonic to it. It's a subtle distinction, but an important one.
Ok!! Makes more sense now..What about plasma membranes? Any functions?
Plasma membranes are very important in this context. The membrane by itself is absolutely impermeable to all charged molecules - for example, these ions everyone keeps talking about, water molecules with a partial charge on them. These things cannot pass through. In that sense, the membrane makes a barrier. It separates the solution outside the cell from the solution inside it. So now you have two separate solutions, it becomes possible to talk about whether outside is hypertonic to inside and vice versa. Without the separation, you would have only one solution so these terms wouldn't be relevant.
It also controls what goes in and out right?
The basic function of the plasma membrane is to hold in everything that is supposed to stay inside the cell, and keep out everything that is supposed to stay out of it. :) It also supports proteins - channels - which selectively let a few of these things pass through. Like water pores that the cell can open and close when it needs to regulate how much water is inside. And receptor proteins that transmit or transport information through the membrane. Like when a cell gets a signal about conditions elsewhere, these receptors take some effect or event that happens outside the cell and regulates how the cell responds.
Alright then!!! And how about comparing eukaryotic and prokaryotic? I know eukaryotes have the nucleus where the DNA is stored. Prokaryotes don't have a nucleus..so they store DNA inside the cytoplasm
That is the defining characteristic, certainly. There are a few other general differences. Size - eukaryotic cells are much, much bigger than prokaryotic cells. You're going to make me try to remember all of these differences, aren't you... ;/
OK, another difference is mode of lifestyle. While there are certainly eukaryotic organisms that live as individual cells, most eukaryotic cells are incorporated in larger, multicellular organisms. And while some prokaryotes are colonial (i.e., they live together, in aggregates), the vast majority of them are free living, single celled organisms.
A third difference is in the nature of their DNA, not just the place where they store it. Eukaryotes organize their DNA into long, linear, stick like chromosomes of which they have more than one. Prokaryotes organize their DNA into a circle or a loop that coils back on itself to make a little ball, and that tends to be their only piece of DNA. Some prokaryotes have multiple small loops of DNA floating around in there, but not so many. And while we're talking about differences in DNA, some or most prokaryotes seem able to exchange pieces DNA with each other. While this never, ever happens with eukaryotes - their DNA is theirs to keep and they do not share.
I'm done with remembering the differences for now, by the way. Hope it's all clear. :)
mannn thats a lot!!
Some of that took dredging up from the depths of my brain - it's been a long time since I answered such questions. :)
Lol! Hahaa how about active and passive transport?
Back to thinking about concentration gradients. Molecules want to "flow down their concentration gradient." Think about packing a whole lot of people into a subway train. The trains pulls up, the doors open, and all these people go from an area of high concentration (inside) to an area of low concentration (the platform). Or about helium molecules in a balloon: you need a lot of pressure to put a high concentration of helium molecules in a confined space. Then you pop the balloon, and for an incredibly short millionth of a moment after the skin is gone, all those helium molecules are hanging in space exactly where they were in a balloon shaped space, all the air molecules are hanging in outside that balloon shaped space. Then time unfreezes and all those helium molecules flow down their concentration gradient, from area of high concentration to the surrounding air. The key is that it takes a lot of effort to pack a high concentration of things in a confined space, while it takes no effort at all to diffuse things from an area of high concentration to an area of low concentration. Active transport happens when cells have to actively use energy and push against concentration gradients - think again about pushing all the helium molecules into the balloon. Passive transport happens when things simply flow down their concentration gradients - it requires no energy at all, so it is a 'passive' process. There was much in that one. :)
Erm, hopefully that whole novella just made sense.
Can you explain the passive transport...a bit more basically?
OK. The key is that molecules want to go from an area of high concentration to an area of low concentration. It takes no energy, the cell has to do no work to make this happen. It just happens all by itself. The passive 'transport' comes in where there is a barrier to diffusion, like a membrane, involved. In that case, it just means that there are proteins in the cell membrane that help these molecules on their way. The molecules are still going down their concentration gradient; they are just doing so with assistance from pores and other proteins, which help them get across the membrane. That's in contrast to active transport, where we are also talking about proteins moving things across the cell membrane - but *against* their concentration gradient, and they need to use a lot of energy to do it.
So is passive transport just letting all the concentration gradient go with the flow?
:) Got it!
I'm glad - these are things I take for granted, but the first time through they are pretty heady concepts.
Haha. Thanks tho! I kinda gotta go now...but thanks for the help!!
Hey medal, please...
Take care. :)
U too! And u might wanna change that number to a 7