annaolivex
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i’m doing aqa biology and in the transport in cells part of the specification it says to explain how the roots and leaves in plants are adapted for exchanging materials? does anyone have any notes or understand what it is i need to know? aqa single science only
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macpatgh-Sheldon
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Good morning Julia (in other words, "Hi" )

Are you doing GCSE or A level ("single science" suggests GCSE)

All you need to know (and which you can actually work out cos God (if you believe in him/her - sorry but I don't!) was not stupid i.e. everything in nature exists/occurs for a logical reason, is as follows:-

1. Large surface area(s):
--- a) Roots branch thousands of times (for e.g. a large oak) especially adventitious roots as in dicotyledonous plants (less so in e.g. carrots with a tap root). They have millions of minute root hairs, which are long and thin (+ unicellular) so extremely large surface area.
--- b) Leaves are numerous (hundreds of thousands in our e.g. above [oak tree]), flat broad shape, so again v v large surface area.

Happy so far?? Yes I can see a smile on your face already -a.a.a.- be careful with that bite of sausage - you don't want to end up with a sore tongue !! . Enjoy your breaky!

2. Look up stomata and guard cells and how a stoma opens and closes with changing levels of e.g. CO2. Again millions of stomata.
3. DAYTIME: more CO2 going in O2 out of leaves (photosynthesis taking place) - conc-n gradients favourable for exchange (look up diffusion). NIGHTTIME: opposite.
4. Very small/thin distance for gases (in leaves) and water/minerals (in roots) to diffuse across e.g. single cell wall plus cell membrane in root hairs, so transport faster, yeah?

RATE OF DIFFUSION is proportional to:

SURFACE AREA X CONC. GRADIENT
……................distance.........................

FROM THIS EQUATION you can predict ALL the above points - think, think, think - don't just try to cram things into your brain as teachers try to make you do - work things out and not only will you remember them for decades, BUT it will also be FUN AND COOL!

Best.
M.
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