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

For this one you could have spoken about how positive feedback amplifies,
Receptors, hypothalamus, sensory, motor, effector, sweating, erector pili lie flat

Original post by aquaticflames

this is correct. I'm so annoyed I didn't think of this. basically the enzymes for respiration slow down, less heat is generated from respiration and therefore the body cools further. oh well! that was a tough one

Reply 61

Livedwards

7

For environment and genes I talked about structural genes and regulatory genes and how these code for different antibodies due to different base sequences so this would lead to variation. Also how the environment(e.g forest, lake) would have different pathogens so different antigens and again different antibodies coded for. This question was so hard I didn’t know if they wanted examples of variation, examples of animals and diseases or control of antibodies by different genes.

Reply 62

kuthik

12

Nah same it was a whole 3 marks as well n I didn’t even know what working to show :frown:

Original post by lionike123

I got 91 so im ****eddddd

Reply 63

Mark Naguib

1

What did you guys get for True False questions?

Reply 64

nicholasflee

13

Original post by nonoui

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

i put physiological

Reply 65

Vorpent

10

yeah it couldn't have been about vasoconstriction for the positive feedback, as vasoconstriction acts as a negative feedback.

it was to do with enzyme activity decreasing = less respiration = less muscle contraction = less heat generated = enzyme activity decreasing = less respiration = less muscle contraction = less heat generated = enzyme activity decreases = less respiration = less muscle contraction = less heat generated = enzyme activity decreases = less respiration = less muscle contraction = less heat generated =enzyme activity decreases = less respiration = less muscle contraction = less heat generated = enzyme activity decreases = less respiration = less muscle contraction = less heat generated = enzyme activity decreases = less respiration = less muscle contraction = less heat generated... you get the point. positive feedback.

Reply 66

Muudeey

15

They overcomplicated the question the substrates would diffuse through every surface and then would need to meet halfway through to fill up the cylinder

Original post by willfoot89

But it was only 2 marks? Like it was 0.8 cause u had to rearrange to formula, they don’t diffuse from one side to the other they only diffuse halfway

Reply 67

AMberrose1234

5

I also but physiological because it was inside the body not anatomical or behaviour then

Original post by nicholasflee

i put physiological

Reply 68

Onisparks

10

I think it also had the mode. I just put the one that wasn't the mean.

Original post by Muudeey

I swear the asking about mean or median. Not mode.

Reply 69

username2199397

18

For the diffusion question were you supposed to work out the surface area to volume ratio?

Reply 70

lionike123

15

You just reminded me about one more answer. He was both wrong and correct. For one of the tables mode appeared twice so you cannot get any hypothesis from that, and for the other one one of the results was an anomalous result.

Original post by Onisparks

I think it also had the mode. I just put the one that wasn't the mean.

Reply 71

username2199397

18

What were you supposed to put for the fructose question? Its was so hard. I wrote that it produced a net ATP of 4 instead of 2

Reply 72

Vorpent

10

you had to work out the diameter, which was 1.6
you re-arranged the formula to find the radius then just times it by 2, followed by the larvae could not use diffusion alone.

the reason it is diameter is because for gases to be exchanged it has to go from the surface, to the centre, and BACK to the surface, hence why it is not 0.8.

Original post by shohaib712

For the diffusion question were you supposed to work out the surface area to volume ratio?

Reply 73

tereziscool

13

it only needs to go to the centre, not back. I saw this another question i did in a past paper.

Original post by Vorpent

you had to work out the diameter, which was 1.6
you re-arranged the formula to find the radius then just times it by 2, followed by the larvae could not use diffusion alone.

the reason it is diameter is because for gases to be exchanged it has to go from the surface, to the centre, and BACK to the surface, hence why it is not 0.8.

Reply 74

Elliefggj

7

I put about it being hydrolysed because a glucose+ a glucose= fructose and glucose is a respiratory substrate, this was a complete guess

Original post by shohaib712

What were you supposed to put for the fructose question? Its was so hard. I wrote that it produced a net ATP of 4 instead of 2

Reply 75

username2199397

18

But fructose is a monosaccharide

Original post by Elliefggj

I put about it being hydrolysed because a glucose+ a glucose= fructose and glucose is a respiratory substrate, this was a complete guess

Reply 76

kKingg

3

I thought it was 0.8 because diffusion of O2/CO2 only needs to travel 0.8cm to reach any cell from the outside? Because it is 0.8mm to the middle of the worm

Original post by Vorpent

you had to work out the diameter, which was 1.6
you re-arranged the formula to find the radius then just times it by 2, followed by the larvae could not use diffusion alone.

the reason it is diameter is because for gases to be exchanged it has to go from the surface, to the centre, and BACK to the surface, hence why it is not 0.8.

Reply 77

Elliefggj

7

Original post by shohaib712

But fructose is a monosaccharide

That’s 2 marks gone then

Reply 78

shcrazy_

5

Physiological

Original post by Stormragexox

i put enviromental adaptations pretty sure its wrong tho

Reply 79

kKingg

3

Also am I the only one who couldnt think of anything for the 6 marker on B and T cells. What were they asking for when they talked about genetic factors? Surely that has nothing to do with immunisation/immune response

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

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