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wrong question

Postby aqudsi » Sun Oct 25, 2009 7:07 pm

i was studyign for my first exam and i came across some previous exam questions some of which seem to be wrong please advise
1- one of the following is FALSE about the plant cell vacuole
a- pumps excess water out of the cell
b- is enclosed by the tonoplast
c- stores organic compounds
d- may contain poisnous compounds

choices a,c, and d are all in my book (campbell-reece) but i couldnt find any mention of the tonoplast in fact i'be never heard of it before, but after searching the internet, this site included i discovered that it exists, and encloses the vacuole so now i dont know what to think...

thats it for now, cheers
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Postby kolean » Sun Oct 25, 2009 9:57 pm

A tonoplast is the name of the cytoplasmic membrane that encloses the vacuole in a PLANT cell, so statement b is true.
I would pick a - pumps excess water out of the cell, as the false statement.
Water can diffuse in and out of the vacuole (does not pump water out for the whole cell, just for the vacuole), so it is not actively 'pumped'. The vacuole uses the active transport of ions to induce water to diffuse in or out of the vacuole. When the ions are pumped in, then water will diffuse in by osmosis, and produce the turgor pressure needed by the plant cell.
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