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HannahC1996
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#2321
(Original post by zbert)
The textbook talks about cohesion of water molecules creates a tension that draws water along the cell walls. Whats that about? :confused:
Oh dear... I don't have a clue! That sounds more like the movement of water up the xylem :confused:
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eilish1903
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#2322
(Original post by philippawright)
Yeah but i'm sure we were told even if it is water, if it doesnt cross a partially permeable membrane it cant be counted as osmosis, its just diffusion? aahhh so confused!
ANY net movement of water from an area of high water potntial to an area of lower water potential is known ad osmosis.
It is osmosis. Trust me

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Tee Logan x
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#2323
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#2323
The capillary is also made of the endothelium layer right?
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zbert
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I'm properly confused because 2 people have said apoplastic pathway is diffusion of water vapour through cell wall.

But in the textbook on page 191 it takes about cohesion tension. Then an answer to the summary question 'difference between apoplast and symplast pathway' is 'apoplastic pathway occurs by cohesion and symplast by osmosis'

So apoplastic pathway is cohesion of water molecules, osmosis or diffusion of water vapour? Which one?
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buzzing22
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#2325
What topics came up last time?
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eilish1903
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(Original post by zbert)
The textbook talks about cohesion of water molecules creates a tension that draws water along the cell walls. Whats that about? :confused:
(Original post by HannahC1996)
Oh dear... I don't have a clue! That sounds more like the movement of water up the xylem :confused:
Thats the apoplastic pathway.

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Suzanna5678
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PLEASE SOMEONE HELP.. If there's a question on how water gets from the root hair cells to the xylem do we talk about apoplastic and symplastic pathways and root pressure?
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eilish1903
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(Original post by zbert)
I'm properly confused because 2 people have said apoplastic pathway is diffusion of water vapour through cell wall.

But in the textbook on page 191 it takes about cohesion tension. Then an answer to the summary question 'difference between apoplast and symplast pathway' is 'apoplastic pathway occurs by cohesion and symplast by osmosis'

So apoplastic pathway is cohesion of water molecules, osmosis or diffusion of water vapour? Which one?
The water doesn't diffuse!!! It is drawn through the cell wall due to the cohesive properties of water.

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zbert
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#2329
(Original post by eilish1903)
Thats the apoplastic pathway.

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So the apoplastic pathway is movement of water by cohesion and is NOT the movement of water/water vapour by osmosis/diffusion?
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PurplePhoenix
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(Original post by Jimmy20002012)
What could we get on things like biodiversity?


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They might just ask something like, "What would the impact be on the diversity of insects if the rainforest was replaced by a single crop?"
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Suzanna5678
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#2331
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#2331
How do we link plasmodesmata to symplastic pathway
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BingTaoBing
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#2332
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#2332
Guys...

why are the grade boundaries for an A so low? I mean, on Jan2010, the boundary was 52/85, which is about 62%...It just seems pretty unbelievable. I don't have a teacher so I can't ask anyone else!
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eilish1903
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(Original post by zbert)
So the apoplastic pathway is movement of water by cohesion and is NOT the movement of water/water vapour by osmosis/diffusion?
Exactly
The symplastic pathway is osmosis

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PurplePhoenix
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(Original post by Bixel)
There's a question in June 2011 that states "Describe how tissue fluid is returned to the circulatory system"

The mark scheme states: "Hydrostatic pressure is lower in capillary, and WATER returns by osmosis"

How comes it mentions water rather than tissue fluid?
Because tissue fluid includes all the small molecules, such as glucose, which make it up. These molecules do not move via osmosis. Osmosis is only water.
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JulianaHiguera
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#2335
(Original post by zbert)
I'm properly confused because 2 people have said apoplastic pathway is diffusion of water vapour through cell wall.

But in the textbook on page 191 it takes about cohesion tension. Then an answer to the summary question 'difference between apoplast and symplast pathway' is 'apoplastic pathway occurs by cohesion and symplast by osmosis'

So apoplastic pathway is cohesion of water molecules, osmosis or diffusion of water vapour? Which one?
Apoplastic is the cohesion of water when it moves through the cell wall, symplastic is the one where it moves via osmosis as one cell obtains a higher water potential than the next drawing water into the next etc Name:  ImageUploadedByStudent Room1370188654.719976.jpg
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Size:  164.8 KB


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eilish1903
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(Original post by Suzanna5678)
PLEASE SOMEONE HELP.. If there's a question on how water gets from the root hair cells to the xylem do we talk about apoplastic and symplastic pathways and root pressure?
Yes!!!

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annac64
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#2337
Has anyone got the jan 13 unit 2 quetsion paper?
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HannahC1996
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(Original post by Suzanna5678)
PLEASE SOMEONE HELP.. If there's a question on how water gets from the root hair cells to the xylem do we talk about apoplastic and symplastic pathways and root pressure?
I definitely think the pathways should both be mentioned but the root pressure is perhaps more relevant to the movement of water up the xylem
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lorobolorolo
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(Original post by HannahC1996)
They are moving against a concentration gradient
Thanks and why exactly is there a higher concentration of ions in the xylem than in the endodermal cells?
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Rachieee123
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Name:  tsr.png
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Size:  3.5 KB Can Someone explain why only 4 amino acids are coded for from this piece of DNA, 3 bases code for an amino acid, aren't there 24 bases so 8 amino acids would be coded for??
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