# Aqa As Biology CourseworkWatch

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#1
Plz could someone help me on my biology coursework
I need to compare the water potential of a potato to a carrot. And I dont have a clue how to set up my experiment so I hope someone can help. Plz plz send me some coursework info or leave an email address so I can ask for it.
0
16 years ago
#2
(Original post by Babyboo2)
Plz could someone help me on my biology coursework
I need to compare the water potential of a potato to a carrot. And I dont have a clue how to set up my experiment so I hope someone can help. Plz plz send me some coursework info or leave an email address so I can ask for it.
ive done a-level biology and ive never heard of measuring a potatos potential !!!!!
can u make it clearer ..
0
16 years ago
#3
(Original post by Babyboo2)
Plz could someone help me on my biology coursework
I need to compare the water potential of a potato to a carrot. And I dont have a clue how to set up my experiment so I hope someone can help. Plz plz send me some coursework info or leave an email address so I can ask for it.
[COLOR=navy]
This is a standard GCSE experiment
take a range of solutions of equal volume - it matters little if they are salt or sucrose. A suitable range might be 0 (i.e. water), 0.2; 0.4; 0.6 0.8; 1.0M. (better would be to combine with a friend who does .1;.3;.5 etc and combine results
Next cut 'chips' of each vegetable, using a cork borer. They should all be the same length and the longer the better - 5cm of so is about right. Note that potatoes are uniform within, whilst carrots have a definite 'core', so you will need to pick the largest carrots you can find, cut them into 6-7 cm lengths and then 'bore' them from top to bottom (i.e. NOT across). For potatoes, it does not matter (as long as they have no skin)
Next, get all 'chips' wet, then blot dry with paper towel (reason below).
Weigh chips
Place in solutions for 30, 60, 90 mins (or whatever)
Remove each chip (mounted needle); blot dry (now you should see why you get them wet to start with); reweigh and replace.
Plot graph[U][B]s of % gain or loss in mass against concentration. Graph should go from +5% or so to -15%; the value where they cross the X-axis (i.e. no change in mass) is the AVERAGE WP of the cells in the 'chip'
Make sure you keep all other factors constant
Easy to think of reasons why method is a bit weak
Science (and biology) behind expt is Fick's Law; osmosis; toxic effects of salt at high conc.
Note that a really good version of this experiment is to compare potatoes of different ages - as the potato matures it loses water, then, as it sprouts it begins to turn starch into sugars.
Quicker version of this is to use banana, which ripens very quickly, so gives results in about 14 days from green to black - just sample a different banana off the bunch ('hand', to be correct) every 2-3 days.
Good luck - if you could not work this out, I think you might need it............
0
16 years ago
#4
I did that coursework before Christmas. You may have done a simular experiment in GCSE with Osmosis. I used a piece of Swede instead of Potato, which we used in GCSE.

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