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AQA A-level Biology 7402 - Paper 3 - 17th June 2019 Unofficial Markscheme

s171958

I was going to finish this question of but the fatty invigilator was like times up I was so pissed 🤣🤣 but never mind at least the 25 marker was nice

Original post by Vfdvf-%

I wrote this too! I’d say 2/3 marks. I didn’t mention a calibration curve, which probably would’ve been the third mark :smile:

Reply 61

s171958

4

Original post by KVJ

What did you guys get for the selection of patients one (who were all female and you couldn’t put their gender or general health)?

I wrote if they are pregnant. And I wrote if they are on any current medication. Dont know if they are right as you needed both points for the 1 mark

Reply 62

Azeee

14

Can someone tell me the way the age of the cancer cell was worked out? Don't remember it and dunno what I wrote

Reply 63

Azeee

14

Anyone remember how many marks the thicker medulla question was? 2 or 3?

Reply 64

Martinmegs

5

how is it a competitive inhibitor it doesn't have totally the same shape, I said non-competitive inhibitor :frown:

Reply 65

Gabzinc

15

Original post by Azeee

Anyone remember how many marks the thicker medulla question was? 2 or 3?

3 marx

Reply 66

g26082000

1

im pretty sure it was a non-competitive inhibitor as it said something like follic acid binds to the DR and the other molecule would bind to the allosteric binding site of DR molecule changing its tertiary structure

Original post by hobicorn

You’d probably have to be more specific and say what kind of inhibitor as there are two types and mark schemes are usually specific with that

Reply 67

Azeee

14

It doesn’t have to be totally the same shape, just similar enough. Also I’ve seen these questions in the past, non competitive inhibitor is also a valid answer so long as you explain why you think so (for competitive it’s easier as you just say they’re a similar shape)

Original post by Martinmegs

how is it a competitive inhibitor it doesn't have totally the same shape, I said non-competitive inhibitor :frown:

Reply 68

Ahsan0916

11

For the heart question I just wrote AV and ventricle. I didnt specify left as it was already pointing at the left side on the diagram so I thought I wouldnt need to. Would I lose the mark because of this ?

Reply 69

Lexib123

4

Me Too!!!! I'm so glad it wasn't only me, what did you write about for the DNA question?? (don't have to tell me if you prefer not too).

Original post by em.parr1

the real question is if bonding is the same as binding because I didn't do that essay on bonding just incase it was only one like hydrogen and ionic bonding

Reply 70

Lexib123

4

I did the same, totally forgot about calibration curves. I think possibly one mark of we are lucky. But probably zero :frown:

Original post by s171958

Hi for the question on cloudiness all I wrote was take sample from each river and measure absorbances using colorimter. How much would this be worth if anything

Reply 71

YellowYellow2

16

Was the question about the light about P values rather than standard deviation?

Reply 72

onlyangel7

11

Original post by Lexib123

I did the same, totally forgot about calibration curves. I think possibly one mark of we are lucky. But probably zero :frown:

I don’t know if we’d need to mention calibration curves, isn’t that for working out concentration? But it just asked for a quantitative measurement so just a number which absorbance would be, not sure though haha

Reply 73

YellowYellow2

16

Original post by onlyangel7

I don’t know if we’d need to mention calibration curves, isn’t that for working out concentration? But it just asked for a quantitative measurement so just a number which absorbance would be, not sure though haha

Yeah I just said that the more the absorbance, the cloudier it is? Unless qualitative means concentration of the precipitate

Reply 74

onlyangel7

11

Original post by Khushi.S

Yeah I just said that the more the absorbance, the cloudier it is? Unless qualitative means concentration of the precipitate

Yeah I said something like that too. Quantitative just means a number value so I don’t think it would have to be the concentration, the absorbance would give you a number that you could compare to other samples if you wanted to?

Reply 75

C342

8

ffs, I wrote photometer not colourimeter

Reply 76

qwertyuiop555

8

Original post by Martinmegs

how is it a competitive inhibitor it doesn't have totally the same shape, I said non-competitive inhibitor :frown:

competitive inhibitors have similar shapes, non-competitive inhibitors don’t

Reply 77

Adam barton

3

pretty sure it was competitive inhibition, it was about preventing the action of an enzyme which helps dna replication by producing nucletides or something, one methyl group doesnt really make the case for hypermethylation of the gene, youd have to say which gene anyway, and the structures of folic acid and trexall were exactly the same apart from a couple hydroxyl and methyl groups

Original post by Alifiahus

I think you’d have to be more specific, I don’t even think competitive inhibition would be accepted? (Unless this is an example of competitive inhibition I’m not sure) There was a methyl group (-CH3) on the diagram, so I wrote that the drug slows down cell division my methylation, the methyl group binds to the promoter region on the DNA molecule, which prevents RNA polymerase from binding, therefore preventing transcription

Reply 78

Adam barton

3

yeah you wouldnt have to do a calibration curve, but you would have to make sure the colorimeter is calibrated to a sample of denionised water before testing the river samples

Original post by onlyangel7

Yeah I said something like that too. Quantitative just means a number value so I don’t think it would have to be the concentration, the absorbance would give you a number that you could compare to other samples if you wanted to?

Reply 79

Yonav King

5

what was the actual answer of the tick box whether it was first or last but the writing??

AQA A-level Biology 7402 - Paper 3 - 17th June 2019 Unofficial Markscheme

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