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AQA A level biology paper 1 2019 Unofficial Markscheme

This poll is closed

AQA A level biology paper 1 2019 difficulty

Great13%

Good34%

Ok39%

Bad10%

Terrible4%

Total votes: 3747

yaseen1000

AQA A Level biology

Non competitive inhib effect on rate:
inhibitor binds to the enzyme away from its A.S
changed hydrogen, ionic and disulphide bridges
Changes tertiary structure
A.S no longer complementary so no more E-S complexes formed / fewer formed per unit time

Table Q:
Cellulose- Algae and Plants
Murein- Prokaryotes
Chitin- Fungi

Why can’t you see any lipid droplets in specimen A
doesnt have a high enough resolution due to light having a high wavelength
OR bile will emulsify all the lipid droplets into small molecules and these small molecules cant be detected by optical microscope as lower resolution

8um and 2um uncertainty
0.8 and 19.2 volumes of water
0.07 concentration
9cm2- 8.1cm2 increase
15.18 x faster for the metabolic rate Q
106 for something lol

BrDU- DNA helicase causes double helix to unwind
Hydrogen bonds break
free nucleotides join onto the exposed template by complementary base pairing
but this time A pairs with Brdu .
catalysed by the enzyme DNA polymerase
H-bonds reform

Water Q -
High Specific heat capacity
Latent heat of vaporisation - allows cooling and homeostatic control
Solvent - o2 and co2 can easily dissolve into it making it a good support medium
Clear - allows photosynthetic organisms to create much needed glucose whilst encompassed by water.
Cohension tension - H bonds formed allows water to flow in xylem tissue

Gas exchange for xerophytes
• little water so guard cells flaccid
• so stomata are closed
• little co2 enters
• slow rate of photosynthesis leads to slow rate of glucose leads to slow rate of respiration so slow rate of mitosis

HIV Q:
Attachment proteins to bind to CD4 receptor
Lipid envelope
Matrix
Capisid with RNA and reverse transcriptase inside

P value Q: if p value is <0.03 then that means the hypothesis is correct because it means you accept it (i.e hypothesis wasn’t due to chance)

How is haemoglobin different to help with increased metabolic rate in mice v horse?
- mouse has low affinity haem
- allows the o2 to dissociate easier at tissues
- increased o2 conc compared to horses
- so more respiration occurring relative to the horse

How does the horses volume to surface area ratio slow down its rate of metabolic reactions compare to mice?:
- respiration causes heat.
- mouse has high metabolic rate but a high SA:V ratio so can cool easier due to evaporation
- horse has a low SA:V ratio meaning metabolic rate has to be slow so it doesn’t overheat as otherwise wouldn’t be able to have constant body temp

What stats test should be used: Chisquared??? (thought it was correlation)

Describe biochemical tests for amylase, lipid and non-reducing sugar:
-Amylase (protein)-Add Naoh-Add biuret reagent-Purple colour
-Amylase - negative test for starch ( add starch, add iodine, if remains blue amylase isnt present)
- Non reducing sugar:-add dilute HCL-warm for 5 mins-Add sodium hydrogen carbonate to neutralise-Add Benedicts reagent in equal volumes-Orange-brown colour
-Lipids-Crush-Add to ethanol-Shake-Add to water-Shake-White emulsion

Describe the conversions of monomer and 2 polymers:

The FFQ question about monitoring fibre over a year or a nurse asking after 24 hours:
Advantage - Larger sample so data is more representative
Disadvantage - People may not remember over a year
Is that right? I left it till last and rushed it heavily

Disadv and Advantage of using hedges:
Advantage: more biodiversity as habitat for more species is preserved
Disadvantage: land for field decreased therefore fewer crops planted, less money for the farmer
Disadvantage could potentially be more plant species (weeds) so more competition and less available resources for farmers crops so less biomass and so on

Describe how the ELISA test....

Fill in gaps:
Allele
Locus
Transcribed
Spliced
Golgi apparatus ( i thought the q said modifies protein) ( some are saying its RER????)
Tertiary

Scroll to see replies

Reply 1

amiraschmuckk

Let’s make an unofficial markscheme here

Reply 2

Evil Homer

TSR Community Staff

Original post by amiraschmuckk

Let’s make an unofficial markscheme here

Will edit the title so that it shows as the markscheme then :smile:

Reply 3

asherk14

found the oxyhaemoglobin graph question really hard

Reply 4

YellowYellow2

I remember getting 0.07 and 0.8 and 19.2 for one of the questions

Reply 5

username2740239

First question - inhibitor binds to enzyme away from active site, changes tertiary structure and shape of active site so substrate no longer fits and enzyme substrate complex can't be made

Reply 6

nosestuckinbooks

Same here! Spent ages on the 0.8 and 19.2 question but I’m not sure if it’s even correct

Original post by Khushi.S

I remember getting 0.07 and 0.8 and 19.2 for one of the questions

Reply 7

username2740239

Original post by Khushi.S

I remember getting 0.07 and 0.8 and 19.2 for one of the questions

Was the 0.07 for the water potential and sodium chloride question? If yeah then i got that as well

Reply 8

YellowYellow2

Original post by 0rg4n1c

Was the 0.07 for the water potential and sodium chloride question? If yeah then i got that as well

Yeah it was
Did you find the mouse haemoglobijn curve really weird to draw?

Reply 9

halim-01

Is the markscheme gonna be harsh :frown:

Reply 10

Heidi-Heather

Original post by 0rg4n1c

Was the 0.07 for the water potential and sodium chloride question? If yeah then i got that as well

I got 0.07 too.

Reply 11

hassan1236945

yeah 0.8 and 19.2 for water and nacl volumes

Reply 12

Pass&fail

- NC inhibitor bonds at allosteric site
- Conformational change at active site, making uncomplimentary
- No enzyme-substrate complexes formed

Original post by 0rg4n1c

First question - inhibitor binds to enzyme away from active site, changes tertiary structure and shape of active site so substrate no longer fits and enzyme substrate complex can't be made

Reply 13

Sabeeya

How does the horses volume to surface area ratio slow down its rate of metabolic reactions compare to mice?

Reply 14

yaseen1000

Mouse has a larger surface area to volume ratio. This means more heat is lossed per gram of tissue and thus the mouse has a higher metabolic reaction in order to maintain body temperature.

Original post by Sabeeya

How does the horses volume to surface area ratio slow down its rate of metabolic reactions compare to mice?

Reply 15

hassan1236945

Mice have larger SA:V ratio so they lose a greater proportion of heat via radiation through skin therefore they must maintain a higher metabolic rate and higher respiration rate which produces more energy to make up for heat loss

Original post by Sabeeya

How does the horses volume to surface area ratio slow down its rate of metabolic reactions compare to mice?

Reply 16

YellowYellow2

Original post by hassan1236945

Ah that’s what it was, I started talking about oxygen and knew it was wrong, I still but mice have a greater SA to vol ratio so should get 1 mark

Reply 17

YellowYellow2

For the fibres question I put
It shows an overall negative trend and is a large sample size so conclusion may be valid
But there is a large difference beyeeen the ranges of the graphs (the standard deviations) so there could be variation in the effectiveness

Reply 18

Musicalsnerd

Probably, since most Biology markschemes are harsh, but it won't be any harsher than usual. However, the grade boundaries for this specific paper are likely to be higher than last year because most people found it to be easier.

Original post by halim-01

Is the markscheme gonna be harsh :frown:

Reply 19

phosphene

cardiovascular disease question anyone? I said

• negative correlation
• steepest change is 10-20g and 40-60g whereas not much difference 20-40g
• no statistical test
• standard deviations never overlap between 10g increments

Also for the xerophyte questions I was unsure?
• higher water potential as need to retain water as not very much available

And gas exchange for xerophytes
• little water so guard cells flaccid
• so stomata are closed
• little co2 enters
• slow rate of photosynthesis leads to slow rate of glucose leads to slow rate of respiration so slow rate of mitosis