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

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Reply 20

lionike123

Yh and if they wanted diameter it would have been four marks. I literally counted the marks per step

Original post by Muudeey

No because the substrate is trying to go into the centre of the cylinder.

Reply 21

shcrazy_

Yes i also got the same but double thought and wrote xylem and phloem nowing full well it wasnt, and then changed it (i think!) this paper was a shambles

Original post by Kwaku54

1. Nucleusous and Vaculoe
Magnification I got 14

Reply 22

EmmaCAnt124

Yeah i got 14,000 too for magnification. 0.80 for the diffuse pathway thing. 50 for bacterial thing at the end. Spores & vector last question. I got two trues and two falses for that box question ... I said don’t use mean because data is nominal not interval .. ( think this is wrong tho) .

Reply 23

toddyz2000

Magnification = 14000x as 2.0x10^-2/1.4x10^-6, Serial dilution I got 5 colonies. Pathway I got 0.8mm.

Reply 24

Xx_InZain_xX

Question 1: Permanent vacuole, Nucleolus, x14000, Magnification not stated, use continuous lines only, no title, no shading etc.
Some other questions I remember
Staining question.
Naked moles body temp is similar to the environment, not the same for most mammals,

Using the mean is more valid because it takes into account the extreme values. Median and mode disregard extreme values and so not all of the data is used hence not as accurate? (Not entirely sure)

Use Unpaired Students T Test to compare the means and see if the difference between the values is significant or not.
Anitbodies usually have 2 binding sites not 3, antibodies have 2 light polypeptide chains not 3? (not sure about the 2nd point)
0.79 for the length of the cell which is < 1 so the organism can rely on diffusion alone.

50 colonies (not sure if its 50 or 5)
Second to last question: Suggest why the student's estimate of the colonies is inaccurate or something?
Last question: Vector, Spores

(edited 4 years ago)

Reply 25

Georgia Lewis

Original post by b987535

lol pretty sure spores arent reproductive

Lol they are. Spores is the correct answer.

Reply 26

Goldenpink

What do you think grade boundaries will be?

Reply 27

olivia-boylan7

Magnification 14000
Diffusion distance 1.6? (2xradius) so could not diffusion
Air space? Nucleus
50 colonies
Vector and spores
Transducer since it could convert one form on energy into a different form I.e chemical to electrical
Don’t use the mean since it was affected by one of the results in the first column

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.

(edited 4 years ago)

Reply 28

nonoui

What's the word for a cold adapted biological molecule?

Reply 29

Xx_InZain_xX

I found paper 3 to be the hardest of the 3 papers :/
What did everyone else think?

Reply 30

Elliefggj

Yeah same, definitely harder in comparison (at least for me anyway)

Original post by Xx_InZain_xX

I found paper 3 to be the hardest of the 3 papers :/
What did everyone else think?

Reply 31

tereziscool

lower than last year unified, potentially even lower than 2017!

Reply 32

medic2400

I said something about hypothermia below optimum conditions for enzymes so less heat generated and therefore body continues to cool down.

Original post by Muudeey

For positive feedback I talked about the enzymes and metabolic reactions(heat is created). Everything else I got similar answers.

Reply 33

Stormragexox

Original post by nonoui

What's the word for a cold adapted biological molecule?

i put enviromental adaptations pretty sure its wrong tho

Reply 34

Xx_InZain_xX

What were the units for the enzyme reaction? I put cm^2/s not a clue though.

Reply 35

Stormragexox

Original post by EmmaCAnt124

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)

lol definitally got really low marks on this paper

Reply 36

Stormragexox

Original post by Xx_InZain_xX

What were the units for the enzyme reaction? I put cm^2/s not a clue though.

i got that too i think

Reply 37

lionike123

Same it was a suggest a units question.

Original post by Stormragexox

i got that too i think

Reply 38

Onisparks

Tbh for the 6 marker I wrote that environmental factors that lead to a weaker immune response are things like immune suppressant drugs, HIV, diet. Strong immune response would be things like vaccination.

For genetics I wrote about inherited illnesses e.g cystic fibrosis, ethnicity, diabetes I.