IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: thecandydoll on September 12, 2010, 05:07:57 am
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Explain, using the term water potential, how water moves from the vascular tissue to
the atmosphere.
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water enters the root by osmosis. after apoplast, vacuolar path and symplast pathway, the water reaches the endodermal(at endodermal water flows in the vacuolar pathway and the symplast pathway) cell and then reaches the xylem vessel.
IN the xylem vessel water move by bulk, this happen due to pressure difference. At the root there is a high pressure of water due to water entering and at leaf there is low pressure due to water leaving the leaf, thus water move up the xylem.water then moves to meshophyll cell by osmosis. Water then evaporate from mesophyll cell to the intercellular air spaces. when the vapour pressure is high enough the stomata open and the water vapour diffuses out!
HOPE IT HELPS YoU :D
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Firstly the water potential of the xylem vessel in the leaves is much higher(less negative) than that of the mesophyll cells. Hence water moves down this water potential gradient by osmosis via the apoplast and symplast pathways into the mesophyll cells.
This water then replaces the thin layer of moisture around the mesophyll cells which allow diffusion of gases to take place. This is because the moisture gets evaporated to water vapour in the intermolecular air spaces which then move down the water potential gradient to the atmosphere via the stomata.
The atmosphere has a much lower water potential gradient that the intermolecular air spaces within the leaves.
However this occurs only during the day when the stomata are open.
If you need further explanation........feel free to ask :)
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+rep Ashish and Deadly King.
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I understood that thanks :D
I have one doubt.
Assuming there is a competive inhibitor,how would you plot the graph of rateofreaction against, substrate concentration
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I understood that thanks :D
I have one doubt.
Assuming there is a competive inhibitor,how would you plot the graph of rateofreaction against, substrate concentration
Competitive inhibition will only decrease the initial rate of reaction. But as concentration of substrate increases the rate of reaction will increase too as the incidence of a substrate combining with an enzyme will be much greater than the incidence of ai inhibitor combining with an enzyme.
Comparing a normal graph of rate against substrate concentration, that with a competitive inhibitor will have a lower gradient initially since rate of reaction is smaller. However both of them will reach compensation point and both graph follows same trend :)
Hope it was clear enough :)