OCR Biology A Breadth - Unofficial Mark Scheme

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1. (Original post by MilindS99)
Last page letters were: C, then ADF (4marks)
(Original post by ImagineCats)
Deffo put AF for the last one so idk if I'd get a mark there
I think i put B,C and ADF, can't even remember what they were now xD
2. (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
== 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:
-

- My solution:
- Advantages: More space for Haemoglobin.

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
I'm just waiting for someone to respond, but I believe the first tuber question would be about controlling variable, like keeping the inital mass of potato disc the same and using the same volume of sucrose solution?
3. (Original post by fw431)
I think i put B,C and ADF, can't even remember what they were now xD
I had that exactly but crossed out B because it was 4 marks not 5
4. (Original post by MilindS99)
I had that exactly but crossed out B because it was 4 marks not 5
I did that in once of the mocks but they sometimes have more letters you need than the number of marks
5. (Original post by M0nkey Thunder)
I'm just waiting for someone to respond, but I believe the first tuber question would be about controlling variable, like keeping the inital mass of potato disc the same and using the same volume of sucrose solution?
I put about controlling variables, i put keeping them in for the same amount of time and making sure sucrose was used to affect water potential each time
6. (Original post by fw431)
I did that in once of the mocks but they sometimes have more letters you need than the number of marks
B was the temperature one, so the rate increases until 25 degrees then decreases at high temp. This did confuse me slightly so i didn't put it down. How is this proof of translocation? (i think part (a) was translocation and (b) proof of source to sink?)
7. (Original post by MilindS99)
B was the temperature one, so the rate increases until 25 degrees then decreases at high temp. This did confuse me slightly so i didn't put it down. How is this proof of translocation? (i think part (a) was translocation and (b) proof of source to sink?)
It relies on active transport, which requires carrier proteins that would denature at high temperatures, bc i think it was asking for proof that it was an active process, and enzymes to turn the sucrose into starch or whatever at the sink
8. (Original post by fw431)
It relies on active transport, which requires carrier proteins that would denature at high temperatures, bc i think it was asking for proof that it was an active process
Indeed.
9. (Original post by MilindS99)
B was the temperature one, so the rate increases until 25 degrees then decreases at high temp. This did confuse me slightly so i didn't put it down. How is this proof of translocation? (i think part (a) was translocation and (b) proof of source to sink?)
It was asking for proof that it was an active process and the only appropriate answer was C because it mentioned that translocation would stop with a drug that inhibits respiration
10. (Original post by Simbak6)
It was asking for proof that it was an active process and the only appropriate answer was C because it mentioned that translocation would stop with a drug that inhibits respiration
Yeah this was my logic too, I didn't see how increasing temperature proved that it was active... i agree with you, I just put C but others are saying B as well so idk if i lost that mark or not
11. (Original post by Simbak6)
It was asking for proof that it was an active process and the only appropriate answer was C because it mentioned that translocation would stop with a drug that inhibits respiration
Surely B's also acceptable then, as the sucrose is actively loaded into the phloem, and these proteins would denature at high temperatures, but also stop working when respiration is inhibited as they could no longer get the energy required to actively transport the sucrose into the sieve tube element
12. (Original post by fw431)
Surely B's also acceptable then, as the sucrose is actively loaded into the phloem, and these proteins would denature at high temperatures?
My logic is that the heat is another seperate thing because it denatures the proteins that load the sucrose, C specifically mentions energy being stopped therefore it is proof.
I'm in the same boat as you I have no idea
13. (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?
The percentage increase was definitely 6600%
Nucleotide bonding was condensation releasing water, yes
Potometers tap not open, yes
I wrote vacuolar membrane, completely forgot the word tonoplast. There was another label to the middle of the vacuole so I think they'd accept vacuolar membrane as well as tonoplast
14. Maths questions:
6600% for percentage increase
1005cm cubed
28% guanine
142607?kilobases
15. (Original post by Simbak6)
My logic is that the heat is another seperate thing because it denatures the proteins that load the sucrose, C specifically mentions energy being stopped therefore it is proof.
I'm in the same boat as you I have no idea
Yeah that's fair enough, i didn't know it it was like the Darwin question on one of the specimens where it included things that could suggested rather than outright proof, depends on wording of the question i guess, if it's straight up proof then i agree they'll probably only allow C
16. (Original post by DaVinciGirl)
I think W was sucrose solution

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I thought W was air spaces :/
17. (Original post by MiracleLeaf)
I thought W was air spaces :/
I got it wrong anyways :/

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18. (Original post by DaVinciGirl)
I think W was sucrose solution

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I thought W was air spaces :/
19. (Original post by MilindS99)
The percentage increase was definitely 6600%
Nucleotide bonding was condensation releasing water, yes
Potometers tap not open, yes
I wrote vacuolar membrane, completely forgot the word tonoplast. There was another label to the middle of the vacuole so I think they'd accept vacuolar membrane as well as tonoplast
The % increase was defo 98.5% 6600 dosnt make sense at all...

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20. For the Plasmodium question... I put about the specific immune system. I said that the antigens cannot be detected on the inside of the cell. Is that completely wrong?

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