it turned out to be a massive questions thread ....

[monokekie]

does anyone know whether they excrete wastes, or store wastes?

[monokekie]

Thanks Biology Moderator *thumbs up*

um,, i got another Q, j/w, what's the difference between hypotonic and hypertonic?

[minilunchbox]

Hypotonic - a solution with less solute than solvent
Hypertonic - a solution with more solute than solvent (think someone who is hyper/hyperactive = lots of sugar)

[simonhu81292]

kekie ... !!!
you do bio? 
wow   

[monokekie]

heh, as you can see, i am just a noob @ bio who has heaps of study to do

[simonhu81292]

is that part of your uni course? a minor or something like that? 

[monokekie]

i am studying biology @ uni  as a subject, 

Hypotonic - a solution with less solute than solvent
Hypertonic - a solution with more solute than solvent (think someone who is hyper/hyperactive = lots of sugar)

and thanks,Minibox

[TrueLight]

Hypotonic - a solution with less solute than solvent
Hypertonic - a solution with more solute than solvent (think someone who is hyper/hyperactive = lots of sugar)

can i just add that when your talking about tonicities... its the total concentration of non-penetrating solute particles on the two sides of the membrane... so if the total concentration of non-permeable solutes is 300 mOsmol/l in solution A (eg.extracellular fluid) and the total concentration of non-permeable solutes is 200 mOsmol/l (eg.intracellular fluid) in solution B. Then water will move from solution B to solution A... so cells would shrink and the extracellular solution is hypertonic to the cells.
the opposite occurs in hypotonic extracellular solutions, where there is a higher concentration of non-penetrating particles in the intracellular compartment compared to the outside, so net water movement flows into the cell and it swells.
and if solutions contain penetrating solutes then they have zero tonicity... even if they have different osmolarities (which takes into account the total concentration of all solutes)....

hmm am i confusing...lol here just read wiki

Osmolarity and tonicity are related, but different, concepts. Thus, the terms ending in -osmotic (isosmotic, hyperosmotic, hyposmotic) are not synonymous with the terms ending in -tonic (isotonic, hypertonic, hypotonic). The terms are related in that they both compare the solute concentrations of two solutions separated by a membrane. The terms are different because osmolarity takes into account the total concentration of penetrating solutes and non-penetrating solutes, whereas tonicity takes into account the total concentration of only non-penetrating solutes.[1]

Penetrating solutes can diffuse through the cell membrane, causing momentary changes in cell volume as the solutes "pull" water molecules with them. Non-penetrating solutes cannot cross the cell membrane, and therefore osmosis of water must occur for the solutions to reach equilibrium.

A solution can be both hyperosmotic and isotonic.[1] For example, the intracellular fluid and extracellular can be hyperosmotic, but isotonic - if the total concentration of solutes in one compartment is different from that of the other, but one of the ions can cross the membrane, drawing water with it and thus causing no net change in solution volume.


ah wait heres a better explanation
http://books.google.com.au/books?id=gOmpysGBC90C&pg=PT94&lpg=PT94&dq=why+do+solutions+of+penetrating+solutes+have+zero+tonicity&source=bl&ots=PNUdgZTbUh&sig=Zs5OSFBrctZ8YR6MZEcLv24O5yc&hl=en&ei=d0CSS6DkM5WekQWVyZyDDQ&sa=X&oi=book_result&ct=result&resnum=8&ved=0CCcQ6AEwBw#v=onepage&q=&f=false

[qshyrn]

Hypotonic - a solution with less solute than solvent
Hypertonic - a solution with more solute than solvent (think someone who is hyper/hyperactive = lots of sugar)

I dont think this is an accurate definition (as nearly all solutions have more solvent particles then solutes). Hypotonic solution means another solution with a lower concentration of solutes RELATIVE to the solution in question (usually solutions on 2 diff sides of membranes), and hypertonic means the same thing except higher conc. relative to solution in question.

[monokekie]

Thanks again, Truelight and Qshyrn for the even more detailed explanations

mmm, i got more questions.... sorry why am i so noob

here goes:

is the following sentence correct?

When placed in water, wilted plants lose their limpness because of osmosis of water into the plant cells.

thanks..

[qshyrn]

Thanks again, Truelight and Qshyrn for the even more detailed explanations

mmm, i got more questions.... sorry why am i so noob

here goes:

is the following sentence correct?

When placed in water, wilted plants lose their limpness because of osmosis of water into the plant cells.

thanks..

yes correct, the osmosis restores the turgidity(stiffness due to water) of the cells

[monokekie]

Thanks!!!!!!!!

also..... is Osmosis the net movement of water from a region of low concentration of water to a region of high concentration of water?

[TrueLight]

well yep if its distilled water.. then you have effectively 0 concentration of non-penetrating solutes... vs the 280 mosmolar or wateva in the plant cells.... so due to the concetration gradient.. the net movement of water flows into the cells.. and because it has the cell wall, it can stand the pressure so there isn't lysis and the plant cells swell

[qshyrn]

Thanks!!!!!!!!

also..... is Osmosis the net movement of water from a region of low concentration of water to a region of high concentration of water?

no(other way around). movement of water from a region of HIGH CONCENTRATION of WATER to a region with a LOW CONCENTRATION OF WATER.

[monokekie]

ahh okay, thanks guys!!

i was completely confused, lolll