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2016 OCR Biology A Breadth - Unofficial Mark Scheme

Please post any questions you remember! If you are confident in the correct answer, please also give what you wrote and any other acceptable answers you may think were available; please also correct me if I am wrong anywhere here
SECTION A
| 1) Microscope (correct row)
| (LM 1,500x mag, 2 micrometers; TEM 500,000x mag, 0.2nm; SEM 100,000x mag, 0.2nm)
| C

| 2) Monomers of disaccharides join by what bond?
| Glycosidic
| Think it was C

| -) Cofactor of Amylase/Prosthetic group of Carbonic Anhydrase?
| Cl-/Zn2+
| @ultralightbeam

SECTION B
POTATO TUBER QUESTION
Which two steps in the procedure should be taken to produce valid results?
- Control the volume of sucrose solution.
- Leave in the solution for the same amount of time.
- Same size of potato tubers.

How can the student use the results to calculate water potential?
- Plot mass change-concentration graph
- x intercept (corresponds to a no change in mass)
- Use value of sucrose conc. with no change with published data for water potential.

Label the parts of the cell. [3 marks]
- I think on this one there was cell wall, plasma membrane, and tonoplast.

What would be found in the gap between the membrane and cell wall in the plasmolysed cell? [1 mark]
- (LABEL W) Sucrose Solution @DaVinciGirl


TRANSPORT QUESTION
State the name of the name of the shift in the oxygen dissociation curve to the right: [1 mark]
- Bohr Effect

BLOOD VOLUMES QUESTION
Percentage change in volume of O2 in saturated blood and saturated plasma? [2 marks]
100×20.10.30.3=6600100\times\frac{20.1-0.3}{0.3}=6600

Erythrocytes have no organelles. Advantages/disadvantages? [2 marks]
- My solution:
- Advantages: More space for Haemoglobin.
- Disadvantages: Short lifespan.

Viruses do not use erythrocytes as host cells; plasmodium does - suggest why? [2 marks]
- My solution:
- Plasmodium is a protoctist.
- It invades the erythrocyte and acts as a parasite.
- As it has no organelles, the virus cannot use this as a host to reproduce.

Volume of oxygen per minute? [2 marks]
- 1005 cm^3 @htrowslec
50.1×20.1=1005dm3\frac{5}{0.1}\times20.1=1005 dm^{3}

NUCLEIC ACIDS QUESTION
Kilobase question with the length of fly DNA.
- 142607 kb (CITATION NEEDED) @MilindS99

Percentage of nucleobase question.
- 28% Guanine @Michelle88222
100(2×22)2=28\frac{100-(2\times22)}{2}=28
(edited 7 years ago)

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I think W was sucrose solution

Posted from TSR Mobile
the question on volume of oxygen in 5 dm of blood was 1005 cm3
Original post by htrowslec
the question on volume of oxygen in 5 dm of blood was 1005 cm3


I got that answer too
2 on multiple choice was glycosidic bond I think
What do you think the grade boundaries are gonna be like??
Reply 6
Original post by Bubblegum2090
What do you think the grade boundaries are gonna be like??


New spec so I think that there is a very good chance of low grade boundaries for two reasons:
A) to make the new spec look good.
B) candidates probably will not do as well as they could in general because of lack of preparatory material (as in, the set of specimen papers and the set of practice papers)
Original post by DoubleDoors
New spec so I think that there is a very good chance of low grade boundaries for two reasons:
A) to make the new spec look good.
B) candidates probably will not do as well as they could in general because of lack of preparatory material (as in, the set of specimen papers and the set of practice papers)


How low is 'low'? 70% for an A?
Original post by TheAlphaParticle
How low is 'low'? 70% for an A?


I'd expect about that if not lower, in past years on the 100 mark paper the grade boundaries have been as low as 64% for an A
Reply 9
Original post by TheAlphaParticle
How low is 'low'? 70% for an A?


last year the grade boundaries were 69%. So, depending on how well people did, it will probably be around the 62-72% boundary for an A.
There was one question asking you to work out the percentage of the bases that were guanine and they told you that 22% of the bases were adenine.

adenine = 22% so thymine = 22%
100 - (22 + 22) = 56
56 / 2 = 28% so percentage of the bases that are guanine = 28%

I can't remember how many marks it was worth though. Probably 2 or 3?
Reply 11
Original post by DoubleDoors
Please post any questions you remember! If you are confident in the correct answer, please also give what you wrote and any other acceptable answers you may think were available; please also correct me if I am wrong anywhere here
Assigned question number and answer
== SECTION A - ALL MULTIPLE CHOICE [1 mark] ==
| 1) Microscope (correct row)
| (LM 1,500x mag, 2 micrometers; TEM 500,000x mag, 0.2nm; SEM 100,000x mag, 0.2nm)
| C

| 2) Monomers of disaccharides join by what bond?
| Glycosidic
| Think it was C

2)

Questions without assigned number
POTATO TUBER QUESTION
Which two steps in the procedure should be taken to produce valid results?
- I put that different concentrations were used and the mass change was recorded.

How can the student use the results to calculate water potential?
- I put 'plot a graph of mass change against concentration, find x intercept, use calibration curve'

Label the parts of the cell. [3 marks]
- I think on this one there was cell wall, plasma membrane, and tonoplast.

What would be found in the gap between the membrane and cell wall in the plasmolysed cell? [1 mark]
- (LABEL W) Sucrose Solution @DaVinciGirl


TRANSPORT QUESTION
State the name of the name of the shift in the oxygen dissociation curve to the right: [1 mark]
- Bohr Effect

BLOOD VOLUMES QUESTION
Percentage change in volume of O2 in saturated blood and saturated plasma? [2 marks]
- My solution:
-where x = plasma value, y = blood value:
-100×yxx=6600100\times\frac{y-x}{x}=6600

Erythrocytes have no organelles. Advantages/disadvantages? [2 marks]
- My solution:
- Advantages: More space for Haemoglobin.
- Disadvantages: Short lifespan.

Viruses do not use erythrocytes as host cells; plasmodium does - suggest why? [2 marks]
- My solution:
- Plasmodium is a protoctist.
- It invades the erythrocyte and acts as a parasite.
- As it has no organelles, the virus cannot use this as a host to reproduce.

Volume of oxygen per minute? [2 marks]
- 1005 cm^3 @htrowslec



If i put sucrose rather than sucrose solution do u think ill still get the mark?
Reply 12
The last question was about mass flow during translocation within plants using the plants vascular system? 4 or 5 marks i cannot remember.

For this q, firstly i said that the plants vascular system is the phloem and xylem vessels then i wrote about translocation and active loading how H+ ions are pumped out, brought back in with sucrose through co-transporter proteins and then diffuse through plasmodesmata into the phloem. Here the hydro-static pressure continues to build up until the sucrose is pushed from an area of high pressure to low pressure. Mass flow is the movement of assimilates such as sucrose in the phloem.

I know i probably overwrote it with some unneeded points but i was too worried about missing something out because ocr have vague questions and super specific mark schemes.
Original post by Simbak6
The last question was about mass flow during translocation within plants using the plants vascular system? 4 or 5 marks i cannot remember.

For this q, firstly i said that the plants vascular system is the phloem and xylem vessels then i wrote about translocation and active loading how H+ ions are pumped out, brought back in with sucrose through co-transporter proteins and then diffuse through plasmodesmata into the phloem. Here the hydro-static pressure continues to build up until the sucrose is pushed from an area of high pressure to low pressure. Mass flow is the movement of assimilates such as sucrose in the phloem.

I know i probably overwrote it with some unneeded points but i was too worried about missing something out because ocr have vague questions and super specific mark schemes.


It was 3 marks I think

Posted from TSR Mobile
Original post by HarrisonGCSE
last year the grade boundaries were 69%. So, depending on how well people did, it will probably be around the 62-72% boundary for an A.


Original post by htrowslec
I'd expect about that if not lower, in past years on the 100 mark paper the grade boundaries have been as low as 64% for an A


The average for an A from 2009 to 2015 was 71% I don't see it going higher than that but it will be nice if its lower. But for some reason our teacher always made is think it was 80% for an A
the one for percentage increase was 98.05% i think. bonding of two nucleotides was condensation reaction, obviously water given out. the multiple choice question about potometers, was that the tap didn't need to be open, the table for the rhino was something like, animalia, phylum, class, genus and sumatrasomething cant remember. Would i be correct if i put permanent Vacuole instead of tonoplast?
Last page letters were: C, then ADF (4marks)
Original post by MilindS99
Last page letters were: C, then ADF (4marks)


Deffo put AF for the last one so idk if I'd get a mark there :frown:
Reply 18
Original post by jbman690
the one for percentage increase was 98.05% i think. bonding of two nucleotides was condensation reaction, obviously water given out. the multiple choice question about potometers, was that the tap didn't need to be open, the table for the rhino was something like, animalia, phylum, class, genus and sumatrasomething cant remember. Would i be correct if i put permanent Vacuole instead of tonoplast?


I didnt think and just wrote vacuole!! also for the percentage one i got 98.5% but rounded it up to 99%. I got the part about condensation and releasing water although i was soo close to writing about phosphodiester bonds. For the order it was
Kingdom
Phylum
Class
Order
Family
Genius
Species.
I think we got basically the same answers woo

what did you write for the 1 mark question about how zoo's are preventing the rhinos becoming extinct other that captive breeding?
Reply 19
There was a 1 mark question about how zoo's prevent the rhinos becoming extinct other than captive breeding (which hadn't worked).

As an answer for this I wrote that zoo's have no poachers so the rhinos cannot be killed e.g. for their horns.
I did originally write about how zoo's have vets which can help ill animals and prevent them from dying, I changed it last minute because i wasnt sure but i'm pretty sure that could have been a potential answer since it was one a 1 marker.

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