Aqa as biology paper 2 2017 unofficial markscheme

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Lazybutmotivated
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#1
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#1
If you could remember any questions post them here so I can put together the markscheme

Differences between glycogen & cellulose (2 marks)
-cellulose has microfibrils
-cellulose has beta glucose monomers

Why glycogen is a good storage molecule (2 marks)
-helical structure
-large molecule
-branched
-insoluble

Chemical test for starch (1 mark)
Iodine/potassium iodine

Magnification (1 mark)
40 micrometers

Type of microscope used & explanation (2 marks)
SEM - 3D image formed

Why volume water was kept constant (2marks)

How to monitor temperature (1 mark)
-use a thermometer

Drawing a curve (1 mark)
Go through all points

affect of higher temperature on light absorption value (2 marks)

Calibration & colorimetry question (4 marks)
-makes solutions of known concentrations
-carry out biuret test
-find value using colorimeter
-plot graph with reading on y-axis & concentration on x-axis

difference in male & female (1 mark)
6 (i think)

rate of decrease in males (2 mark)
5/35 = 0.143

why a large number of AMY1 genes was advantageous (3 marks)
more colloisions between enzyme & substate so more e-s complex formed

natural selection of large number of amylase genes (3 marks)

why old people are more likely to catch infectious disease (1 mark)
-have less antibody in blood

working out ratio (1 mark)
-number below 1 (dont remember exact value)

why substance helps plants that live in dry conditions (3 marks)
-stomatal openings decrease, so less transpiration
-helps conserve water

why substance helps things from entering through stomata (2 marks)
Reduces diameter size so cannot enter down the concentration gradient into the plant & cause infection

How to work out diameter of stomata (3 marks)
-measure length with graticule & calibrate against something of known length

why conclusion is not valid (3 marks)

Why there was a Mutation (2 marks)
-non-disjunction

Why all body cells have mutation (3 marks)
-body cell divide by mitosis to form clones

how an s-shaped dissociation curve is formed (2 marks)
-binding of first oxygen molecule changes shape, making it easier for the other oxygen molecules to bind

advantage of having adult haemoglobin (3 marks)
-lower affinity,so more oxygen unloaded at respiring cells so greater rate of respiration

Why an increase in fetus haemoglobin is advantageous (3 marks)

question on monoclonal antibodies (1 mark)
-will bind to antigen, preventing it from binding to receptors on nerve cells

why antibody is specific (4 marks)
-specific base sequence so specific primary structure
-particular hydrogen-ionic bonds in tertiary structure so specific tertiary structure
-binding site only complementary to antigen to form antibody-antigen complex

Why children may die with the disease (3 marks)
-less blood in aorta so less oxygenates blood to respiring tissues so less respiration

Cohesion-tension theory (5 marks)
-water evaporates from mesophyll cells by transpiration
-this lowers wp
-water enters by xylem
-creates tension
-water is cohesive so forms a continuous column
-water is pulled upwards from the roots to the stem

How mRNA is formed in plants (5 marks)
-an enzyme breaks h-bonds between polynucleotide stands
-strands can act as templates
-free flowing nucleotide join exposed bases by complementary base pairing
-this reaction is catalysed by enzyme polymerase
-splicing occurs to remove introns, allowing exons to join together
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Gerry-Atricks
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#2
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#2
https://www.thestudentroom.co.uk/sho...4#post71917904
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Lazybutmotivated
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#3
Il just add those here
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Gerry-Atricks
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#4
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Cellulose- beta glucose, hydrogen bonding, microfibrils, unbranched
Glycogen- alpha glucose, branched

Starch good for storage- amylopectin branched ( 1,4 and 1,6) help give it a very compact shape, lot of energy stored, insoluble-doesnt affect osmotic potential

Mutation question- non disjunction is failure of separation of chromosomes in meiosis meaning one cell has an extra copy and one is missing one-can lead to e.g downs and turner respectively ( i dont think this was the question btw)

Cohesion tension theory- cohesion between water molecules, delta negative oxygen attracts delta positive hydrogen and drives transpiration stream, adhesion also adds to this effect as cell wall molecules repel water, allows water to travel as a stream, purely passive process, when water removed from leaf by transpiration, osmosis causes water molecule to replace it and cohesion tension causes whole stream to rise from roots to leaves.

mRNA produced when a cistron unwinds exposing bases (unwinds with the help of dna helicase and RNA polymerase) , attracts free complementary bases/ nucleotides which join up to it, Uracil is attracted to adenine,not thymine. Mrna strand then separates and is used as template in translation, 3 bases code for one amino acid, codon on it pairs with anticodon to make proteins.
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Gerry-Atricks
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#5
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#5
(Original post by Lazybutmotivated)
If you could remember any questions post them here so I can put together the markscheme

Differences between glycogen & cellulose (2 marks)
-cellulose has microfibrils
-cellulose has beta glucose monomers

Why glycogen is a good storage molecule (2 marks)
-helical structure
-large molecule
-branched
-insoluble

Chemical test for starch (1 mark)
Iodine/potassium iodine

Magnification (1 mark)
40 micrometers

Type of microscope used & explanation (2 marks)
SEM - 3D image formed

Why volume water was kept constant (2marks)

How to maintain constant temperature (1 mark)
-use a water bath
Calibration & colorimetry question (4 marks)
-makes solutions of known concentrations

How to work out diameter of stomata (3 marks)
-measure length with graticule & calibrate against something of known length

Where there was a Mutation (2 marks)
-non-disjunction

Why all body cells have mutation (3 marks)
-body cell divide by mitosis

Why children may die with the disease (3 marks)
-less blood in aorta so less oxygenates blood to respiring tissues so less respiration

Cohesion-tension theory (5 marks)

How mRNA is formed in plants (5 marks)
All body cells have mutations because of mistakes made in DNA replication, insertion/deletion/substitution etc, different amino acid made ( if mutation large enough), different proteins made. Mutation can also be hereditary or environmental. Then cells divide by mitosis so mutated DNA replicated
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GCShElpme
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How did you guys find it? I'll type up what I can remember in a minute!
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Lazybutmotivated
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#7
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#7
(Original post by GCShElpme)
How did you guys find it? I'll type up what I can remember in a minute!
I found it easier than the first paper
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unimatrix79
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Old people are more likely to suffer from infectious diseases. suggest why this may mean they have less protein in the blood? [1 mark]explain AMY1 gene adaptation in those with high starch diet in terms of natural selectionUse your knowledge of protein synthesis and enzymes to explain why extra AMY1 copies are advantage(i think) hese are probably worded wrong lol but was the jist
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unimatrix79
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#9
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98% is hbF but by 6 months almost all hbA - explain why this is an advamtage for the baby
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inurdreams2000
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#10
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#10
[QUOTE=unimatrix79;71919640]Old people are more likely to suffer from infectious diseases. suggest why this may mean they have less protein in the blood? [1 mark]

I wrote because there are less antibodies
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jazz_xox_
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#11
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#11
So many people saying that was better than the first paper I found the first one quite good but there was so many in this that I was unsure about!! The calibration one I had no clue , and the one on natural selection due to the genes, I was confused because surely you're not more likely to survive if you can digest starch better? And I accidentally missed out the one to calculate the rate
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jazz_xox_
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#12
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#12
Use eyepiece graticule to measure mean diameter of stomata
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FabStudent
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#13
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(Original post by unimatrix79)
Old people are more likely to suffer from infectious diseases. suggest why this may mean they have less protein in the blood? [1 mark]explain AMY1 gene adaptation in those with high starch diet in terms of natural selectionUse your knowledge of protein synthesis and enzymes to explain why extra AMY1 copies are advantage(i think) hese are probably worded wrong lol but was the jist

For the first question I thought it was - Old people have less protein in the blood how does this lead to more infections?
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FabStudent
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#14
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#14
(Original post by Lazybutmotivated)
If you could remember any questions post them here so I can put together the markscheme

Differences between glycogen & cellulose (2 marks)
-cellulose has microfibrils
-cellulose has beta glucose monomers

Why glycogen is a good storage molecule (2 marks)
-helical structure
-large molecule
-branched
-insoluble

Chemical test for starch (1 mark)
Iodine/potassium iodine

Magnification (1 mark)
40 micrometers

Type of microscope used & explanation (2 marks)
SEM - 3D image formed

Why volume water was kept constant (2marks)

How to maintain constant temperature (1 mark)
-use a water bath
Calibration & colorimetry question (4 marks)
-makes solutions of known concentrations

How to work out diameter of stomata (3 marks)
-measure length with graticule & calibrate against something of known length

Where there was a Mutation (2 marks)
-non-disjunction

Why all body cells have mutation (3 marks)
-body cell divide by mitosis

Why children may die with the disease (3 marks)
-less blood in aorta so less oxygenates blood to respiring tissues so less respiration

Cohesion-tension theory (5 marks)

How mRNA is formed in plants (5 marks)
I thought the question was how do you make sure the temperature is constant not 'How to maintain constant temperature' I literally wrote check the temperature at regular intervals but now im thinking you're right - facepalm-
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brrrigid
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#15
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#15
(Original post by jazz_xox_)
...surely you're not more likely to survive if you can digest starch better?
I put in the event of a famine where non-starch foods were eliminated, individuals who could digest more starch and form more amylose (by extension energy) would have a better chance at survival than those who could not digest as much. Therefore the individuals with more copies of the gene would survive, and those without as many would die.
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tippypro
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#16
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#16
Did anyone say the ELIZA test for the calibration curve of proteins.
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jazz_xox_
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Makes sense, I wasn't thinking of the sense of a life or death thing lol, I did say they're more likely to be healthier, survive and reproduce and would pass on the their allele more often? Is it an allele that would cause the more production? Threw me right off .. hope I can still get an A, hated that paper
(Original post by brrrigid)
I put in the event of a famine where non-starch foods were eliminated, individuals who could digest more starch and form more amylose (by extension energy) would have a better chance at survival than those who could not digest as much. Therefore the individuals with more copies of the gene would survive, and those without as many would die.
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jazz_xox_
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For the microscope I said TEM as you could see small organelles such as the starch grain because of the high res?
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brrrigid
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#19
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#19
(Original post by jazz_xox_)
Makes sense, I wasn't thinking of the sense of a life or death thing lol, I did say they're more likely to be healthier, survive and reproduce and would pass on the their allele more often? Is it an allele that would cause the more production? Threw me right off .. hope I can still get an A, hated that paper
It said it was a AMY1 gene, and some populations have more copies of it. Yeah, the passing on of the gene I think was key to it.

I didn't really like either of the papers - they were not terrible by any means, but they weren't easy either. Glad I have this experience for next year (:

And for the microscope question I put SEM because it was a 3D image.
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Mil23333
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#20
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#20
(Original post by FabStudent)
I thought the question was how do you make sure the temperature is constant not 'How to maintain constant temperature' I literally wrote check the temperature at regular intervals but now im thinking you're right - facepalm-
I thought this too!!!!
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