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AS biology

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ruby92:
M/J 2003
paper 1

19
4
18
29
25

tmisterr:
19. answer is C. in semi-conservative replication, the new DNA helix has one old strand and one new strand so the number with nitrogen 15 keeps on reducing by half.

18. answer is A. each tRNA molecule is specific to one amino acid so all you need is 4 tRNA since the polypeptide chain consists of only these four, repeating themselves, so the tRNA molecules can be re-used

4. if they have the same water potential, osmosis will be at equilibrium so water moving into cells will equal water moving out so in the end, there will be no change in length so initial length/final length will equal to 1. read of graph, answer is 0.45 i.e C

29. C, vital capacity is the maximum amount of air breathed in, and then breathed out.

25. C again, the more negative the water potential the lower the water potential, and as u know water movers from high to low water potential so it moves from high water potential in cell 3 (-4kPa) to a lower water potential in the environment (-5kPa) and from the environment into cell 1 which is at an even lower water potential (-7kPa)

ruby92:
@timsterr
thnkx a loooottttttt  :D

tmisterr:
no problem!

ruby92:
m/j 2004
7
4
5
23-hw is it b wont it be D
30

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