Betsy_Lou
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#1
Report Thread starter 2 years ago
#1
Hey,

I'm really worried Mass Flow Theory is gonna come up on the AQA biology paper next week, and I don't understand it.

In the textbook it says that sucrose molecules are co-transported out of companion cells with hydrogen ions, but EVERYWHERE else says sucrose is actively transported out (not co-transported).

Can anyone clear this up for me?
If I write about co-transport (provided there's a question on it), will I achieve the marks, as that's what the textbook says?
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Banzen
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Report 2 years ago
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• Mass flow from source to sink
• In source/leaf sucrose actively transported into phloem (ATP against concentration gradient)
• By companion cells
• Lowers water potential of sieve tube cell and water enters by osmosis
• Increase in (hydrostatic) pressure causes mass movement towards sink/root
• In root sugars/sucrose used for respiration or converted to starch for storage

Hope this helps!
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