OCR A-Level Biology Paper 3 17th June 2019 - Unified Biology [Unofficial Markscheme] Watch

Silent0239
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I couldn't find a thread for today's paper and I am really curious what y'all put for your answers.
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Kwaku54
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1. Nucleusous and Vaculoe
Magnification I got 14
(Original post by Silent0239)
I couldn't find a thread for today's paper and I am really curious what y'all put for your answers.
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username2185437
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I got 14 000, don’t know if it’s right
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ottz
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For calculations i got 14000x 0.7 something cor the radius and 50 for the dilution
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Elliefggj
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I got 15 000 for the magnification
(Original post by sabrina1999)
I got 14 000, don’t know if it’s right
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EmmaCAnt124
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2019
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EmmaCAnt124
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Serial dilution answer : 50.
Diffusion pathway : 0.80 - can use simple diffusion pathway as less than 1mm.
Units for enzyme rate : mms^-1
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b987535
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what did you get for question 3? i got 17.5 (1dp)

any thought?
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delayedsc
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Weren't the units mm^2 s-1 as it was measuring area?
(Original post by EmmaCAnt124)
Serial dilution answer : 50.
Diffusion pathway : 0.80 - can use simple diffusion pathway as less than 1mm.
Units for enzyme rate : mms^-1
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EmmaCAnt124
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Last fill in the gaps : vector & spores
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b987535
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(Original post by EmmaCAnt124)
Last fill in the gaps : vector & spores
are you sure? i put vectors and gradients???
please tell me im not dumb....
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EmmaCAnt124
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Stain improvement : Wet mount procedure , add stain from the side of the cover slip , use more than on stain.
- biological drawing improvements : State magnification , do not add details to organelles , add scale , Make sure drawings are an accurate representation of actual image ( eg rectangle vs circlw)
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cara_mckee
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I put spores, because they're reproductive
(Original post by EmmaCAnt124)
Last fill in the gaps : vector & spores
(Original post by b987535)
are you sure? i put vectors and gradients???
please tell me im not dumb....
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sophiakent
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For the 1st 6 marker I wrote about bone marrow disease and effect on t lymphocytes for genes, would this be correct ?
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b987535
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(Original post by cara_mckee)
I put spores, because they're reproductive
lol pretty sure spores arent reproductive
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lionike123
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Staining Question:
- Ensure that there are no air bubbles.
- He never added any dye, he only talked about how to place the sample in the slide.
Positive Feedback question:
- Thermoreceptor transmits impulses to the hypothalamus. Hypothalamus triggers a series of reactions such as vasoconstriction and hairs lie flat. Action Potentials will continue to be generated and therefore positive feedback.
Microorganisms Question: Talk about quorn, cheese, bread and which microorganisms it uses. Many advantages such as they can easily be genetically engineered, population size can be controlled by controlling factors like temperature, they can use waste materials.
Batch vs Continuous:
- 1) Continuous 2) Batch 3) Batch 4) Continuous
Immunity and Variation Question:
- Talk about CD4 receptors in T-helper cells, mutations, how a gene codes for a protein which is an antibody and has different primary structure, secondary structure and the bonds within. The environment you can talk about how there are different pathogens in the environment, animals that live in sterile conditions have a weaker immune system as they have not developed an immunological memory from B-memory Cells. You can then talk about autoimmune responses.
Normal Antibody vs the other antibody:
- The antibody in the drawing can bind to 3 antigens( 3 variable regions) whereas in normal antibody it can bind to 2 antigens.
- The antibody in the drawing cannot bind to phagocytes whereas normal antibodies can.
Volume of cylinder question was 0.78(did not specify significant figure to use).
Last question was vectors and spores.
First question was vacuole and nucleus. Confirmed check here: https://www.sciencephoto.com/media/9...plant-cell-tem
one of the differences question i talked about how it cannot trigger an action potential as voltage gated sodium ion channels close when H+ is present.
Physiological Adaptation question was Environmental.
Students T-test was one answer as well.
I messed up magnification i timesed by 100 rather then divide by 100.
Differences between mammals and the rat( or what ever it was): Mammals can maintain a constant internal environment despite external changes such as temperature whereas the rat( or whatever it was) was dependant on temperature. Also, mammals can live in a greater variety of habitats whereas the rat can only live in the underground.
Mean, mode median question: Both wrong and correct. One of the tables he included the anomalous result to calculate mean so it was wrong. One of the tables he got two modes which you cannot do any statistical test on.
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Muudeey
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pretty darn good paper except for the fact none of the hard **** I memorised didn't come up
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letapyikut
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For the radius question do you not have to times by 2 to get the diameter
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Muudeey
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(Original post by lionike123)
Staining Question:
- Ensure that there are no air bubbles.
- He never added any dye, he only talked about how to place the sample in the slide.
Positive Feedback question:
- Thermoreceptor transmits impulses to the hypothalamus. Hypothalamus triggers a series of reactions such as vasoconstriction and hairs lie flat. Action Potentials will continue to be generated and therefore positive feedback.
Microorganisms Question: Talk about quorn, cheese, bread and which microorganisms it uses. Many advantages such as they can easily be genetically engineered, population size can be controlled by controlling factors like temperature, they can use waste materials.
Batch vs Continuous:
- 1) Continuous 2) Batch 3) Batch 4) Continuous
Immunity and Variation Question:
- Talk about CD4 receptors in T-helper cells, mutations, how a gene codes for a protein which is an antibody and has different primary structure, secondary structure and the bonds within. Environment you can talk about how there is different pathogens in the environment, animals that live in sterile conditions have a weaker immune system as they have not developed an immunoligical memory from B-memory Cells.
Normal Antibody vs the other antibody:
- The antibody in the drawing can bind to 3 antigens( 3 variable regions) whereas in normal antibody it can bind to 2 antigens.
- The antibody in the drawing cannot bind to phagocytes whereas normal antibodies can.
Volume of cylinder question was 0.78.
Last question was vectors and spores.
First question was vacuole and nucleus/or nucleolus( mark scheme will say both).
For one of the differences question i talked about how it cannot trigger an action potential as voltage gated sodium ion channels close when H+ is present.
Physiological Adaptation question was Environmental.
Students T-test was one answer as well.
For positive feedback I talked about the enzymes and metabolic reactions(heat is created). Everything else I got similar answers.
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Muudeey
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(Original post by letapyikut)
For the radius question do you not have to times by 2 to get the diameter
No because the substrate is trying to go into the centre of the cylinder.
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