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PettitN
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#4261
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#4261
(Original post by The Lawful T.J)
Aha! I put that it's a quarternary structure, and it has 4 polypeptide chains..
then went on to talk about the amino acid sequence and how they would differ... or something ><
yhh i put this too.
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unknown guy
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#4262
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#4262
For the spiracle question i said it opens 4 seconds every 18 seconds, 3lots of 18 in a minute so 3 times 4 equals 12(it said per minute in answer)

I thought that was defintely right?am i wrong
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anamullah
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#4263
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#4263
(Original post by PettitN)
I did 5 days revision for this exam. For me personally this works for me with biology. I dont think this was a particulary hard exam but markschemes tend to give answers no sane person would think of. To be honest i dont think revising weeks and weeks for this exam would have made any difference as the answers involved a small amount of knowledge of the subject and was more to do with common sense. I guess it was more about understanding it rather than knowing it.

After looking through the Unofficial markscheme i can say that i have lost between 12-21marks which i think may be a B or just scrape the A grade.

Just got chemistry to do now and im freeeeeee.... until monday when we have to go back to do A2 stuff.


where is the unofficial markscheme??
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Bobby2
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#4264
(Original post by Helpfulstudent)
So many people have asked why the answer was 6 (some have said 7 etc) for the insect ventilation graph question.

heres what I think. (I've attached pictures) the first one is what I remember from the exam, the second is a real life example from an actual gas exchange pattern for a fly)
Attachment 222775
Attachment 222773
So what is the right answer?
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cheetahs56
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#4265
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#4265
(Original post by dooobie_)
I think the grade boundaries will be

A - 58
B - 52
C - 46
D - 40
E - 34
I predict:

A- 61
B- 57
C-53
D-49
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richarddawkins
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#4266
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#4266
BIOL2 UNOFFICIAL MARK SCHEME

1a(i) Centromere [1]
a(ii) attaches to spindle fibres; and splitting during anaphase [2]
b) different alleles [1]
c) the chromosomes had divided into chromatids [1]
d) three chromosomes drawn; different shape [2]
d) Crossing over [1]
2a) groups of organisms; that interbreed to produce fertile offspring [2]
b) 6.98/7;; [2]
c) less plants; less habitat; less food variety [3]
3a) groups within groups; no overlap [2]
b) shows evolutionary relationship [1]
c) least different/most similar amino acids sequence; most similar base pairs; more a.a seq= more closely related [2]
d) B and C had different differences so different amino acid sequences [1]
e) all organisms have it [1]
4a) Sample 1: 15N only;
Sample 2: 14N/15N;
Sample 3: 14N/15N and 14N only [3]
b) breaks H bonds in DNA; between complementary base pairs; unzips the strand [2]
c) binds with guanine; complimentary base pair can’t form; DNA can’t zip back [2]
d) cancer cells as they divide more frequently [1]
e) prevents formation of cell wall; osmotic lysis [1]
5a) vertical gene transmission; passes resistant gene to next generation [2]
b) (The scientists used many patients) to make results more reliable [1]
c) (True) Hypochlorite had most no. of bacteria killed;
(False) SD overlap so no real difference/more likely to be chance; no control dish used; need to test on more disinfectants [3]
d) Mutated; resistant gene; [2]
6a) Quaternary: Haemoglobin only
Condensation: All 3;
Nitrogen: Haemoglobin only [3]
b) 16%. [1]
c) (The fetal haemoglobin had) a higher affinity; associates/loads oxygen more readily [2]
d) respiration occurs; haemoglobin has lower affinity; oxygen unloaded easily for respiration. [2]
e) (no symptoms because) adult haemoglobin present [1]
7a) (Founder effect is when) few/30 individuals from Swiss population colonised a new region; fewer different allele/reduced gene pool; (making it) less genetically diverse; inbreeding; [3]
b) 250,000. [1]
c) mutation; three bases removed [2]
d) amino acid sequence changes; tertiary structure changes; non functional active site, e-s complex can’t form [2]
8a) mineral ions actively transported to xylem; WP gradient in xylem reduced; water enters xylem by osmosis; water evaporates/transpires via stomata; WP in leaf cells reduced; water drawn up from xylem (by osmosis); creates tension; water molecules cohere/H bonding; continuous column of water [6]
b) (abdominal musle movement) ventilates air; maintains concentration gradient; O2 diffuses in/CO2 diffuses out [2]
c) (small insects have) large SA:Vol ratio [1]
d) 6.7;; [2]
e) 342 % ;; [2]
f) (removal of water) increases O2 conc. in tracheoles/shortens diffusion pathway [1]
9ai) age; species; health conditions? [2]
aii)) (different males used) so previous tests did not influence results; [1]
aiii) Avoid bias [1]
aiv) Paper with no lipid from female [1]
b) (Conclusion was that) length of female was more influential than lipid...? [2]
c) (2 benefits of longer females) more eggs; better predator; successful mating; [2]
d) longer the female, greater the unsaturated fatty acid %; males attracted to high fatty acid% so more attracted to longer females (who have that) [2]
ei) Draw line of best fit; extrapolate [2]
eii) (beyond 75cm) exceeds 100% (so unlikely); [1]
f) (female) won’t recognise/respond [1]

(not mine i just copied it from earlier in the thread so people could see it)
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Helpfulstudent
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#4267
(Original post by anamullah)
where is the unofficial markscheme??

http://www.thestudentroom.co.uk/showthread.php?t=2233709&page=20 5&p=42941628#post42941628
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Mehroze1
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#4268
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#4268
(Original post by anamullah)
where is the unofficial markscheme??
page 205 of this thread
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AdamskiUK
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#4269
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#4269
(Original post by Chrisd00100)
It would open every 16 seconds. If you divide a 60 by 16, it would be 6.75 or something. But of course you can't say 6.75 times, but 6 times. Not 7 because you can't round it in this case
Right answer, wrong method.

You measure peak to peak, and so it was open for 2 seconds and after that it took 8 seconds to get to the next opening. Therefore you say 60 seconds / 10 seconds per spiracle opening = 6 times per minute.

Some argued that you take the 2 seconds off of 10 seconds and use 8, but that's impossible. Just because the spiracle is open doesn't mean time is erased. It is open for 6 times in 60 seconds, and you can't just wish away 12 seconds of that just because the spiracles were open.
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richarddawkins
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#4270
(Original post by The Lawful T.J)
Aha! I put that it's a quarternary structure, and it has 4 polypeptide chains..
then went on to talk about the amino acid sequence and how they would differ... or something ><
wait yeah this is pretty much what i wrote
i said something about the quaternary structure, more than 1 polypeptide chain, means more than one amino acid sequence and they cannot be compared

utter bull**** or will that scrape me a mark?
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AdamskiUK
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#4271
(Original post by Swords N Thorns)
I said it has a slightly different shape in different organisms since some organisms have a higher affinity for O2 and some have a lower affinity...no idea if it is right though.
Pretty sure that's the right answer. Think about it; Hb alters itself depending on the P(O2) available to a colony of species. Higher altitudes changes Hb's affinity for oxygens. There's a lower P(O2) and therefore, a higher affinity to take up as much as the organism can.
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VigneshSB
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#4272
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#4272
What ums will 75/76 get?
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Helpfulstudent
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#4273
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#4273
(Original post by Bobby2)
So what is the right answer?
Not exactly sure because I don't remember the actual values on the graph but I said that it was 6. my explanation is on the first picture. (click on it to enlarge)
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dooobie_
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#4274
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#4274
I read that haemoglobin varies in different species and is uncomparable and thats what I wrote?
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Jimmy20002012
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#4275
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#4275
(Original post by VigneshSB)
What ums will 75/76 get?
Guessing that's full ums


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Helpfulstudent
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#4276
(Original post by AdamskiUK)
Right answer, wrong method.

You measure peak to peak, and so it was open for 2 seconds and after that it took 8 seconds to get to the next opening. Therefore you say 60 seconds / 10 seconds per spiracle opening = 6 times per minute.

Some argued that you take the 2 seconds off of 10 seconds and use 8, but that's impossible. Just because the spiracle is open doesn't mean time is erased. It is open for 6 times in 60 seconds, and you can't just wish away 12 seconds of that just because the spiracles were open.
completely agree. here's a visual explanation to add to this
Name:  Screen shot 2013-06-03 at 18.37.10.png
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rugbymad123
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#4277
(Original post by walkers38)
The conclusion was that length of female was more influential than lipid.
Wasn't it that the lipid was more influential than the presence of the actual female snake since there was the same response with and without the female itself and just with the lipid on the paper.
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Elle333
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#4278
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#4278
I wrote only about water potential and osmosis and explained fully apoplast and symplast pathways for 6 marker. What would I get? x


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constandinos
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#4279
anyone got the paper ?? if yes pls send it to me !!!
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amyb96
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#4280
c) mutation; three bases removed [2]

i put a mutation that caused triplet code to become none coding- an intron? would that be okay?
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