Turn on thread page Beta
    • Community Assistant
    • Thread Starter
    Offline

    20
    ReputationRep:
    Community Assistant
    Since I've seen a lot of people asking for the unofficial mark scheme, I thought: why not make a thread? Now, no-one's memory is absolutely perfect so we need to work together to remember the questions (and hopefully the answers). Thankfully, I remember the very first question (albeit not the actual wording of the question) but feel free to contribute your own and I'll stick it on the post.

    Granted, I don't have much to contribute right now but I'm sure as people join in, we'll build up a right good answer list!

    Press "show" below to see all of the answers and questions we have collated

    Spoiler:
    Show



    Ribosomes are made up of what molecules? (1 mark)
    Protein and rRNA

    Describe how ribosomes are used to make polypeptides. Do not include transcription in your answer. (~3 marks)
    mRNA travels out of the nucleus onto the RER where it slots into the groove between the unit and subunit of a ribosome. As ribosome translates the mRNA, complementary tRNA anticodons deposit amino acids that are joined by peptide bonds, creating a polypeptide chain.

    Describe the structure of glycogen (2 marks)
    a-glucose with 1-4/1-6 so heavily branched and compact due to helical shape (it does helical up)

    Describe how glycogen is a good energy source in animals (2 marks)
    Readily hydrolysed the glycosidic bonds to give off energy and to produce ATP following aerobic respiration. Lots of ends mean higher surface area, so more hydrolysis

    What two adaptations does the cell membrane in the uterine lining have that makes it efficient for nutrient transport (2 marks)
    Many protein carriers, thin membrane

    Explain the action of the H+/Na+ Pump (3 Marks)
    Both bind to seperate areas, ATP hydrolysis used to change protein shape to move Na+ against the gradient and then H+ moved out

    Explain all the scientists results (Why mass increased and P value meaning) (4 Marks)
    Mass increased because salt stayed high in gut so wp lowered, causign water to move in via osmis. P value of <0.05 meant that % due to chance was less than 5% so significant.

    Increased salt results in tissue fluid build up, explain why. (2 Marks)
    More molecules move out because of increased hydrostatic pressure but water potential is lower in tissue fluids, so less tissue fluid can reenter the blood. Lymphatic system cannot completely drain excess fluid

    Explain the shape of the curves at 50°C and 60°C
    60°C declined more rapidly due to the high amounts of heat energy causing the bonds to be broken, therefore changing the tertiary structure of the enzyme and meaning it no longer has a complementary active site to the substrate so is rendered ineffective. The same thing happens at 50°C, but more slowly as there is less heat energy to break the bonds between the amino acids.

    Describe and explain the advantage of bacteria secreting extracellular protease (2 marks)
    Some proteins are too large to enter the cells through diffusion or do not have the specific cell membrane carrier proteins. By breaking the proteins down out of the cell, the bacteria can then take up the smaller proteins and amino acids that it needs.
    Also, by secreting protease, antibodies can be hydrolysed, therefore protecting the bacteria.

    Describe the action of membrane bound dipeptidases and explain the advantage (2 marks)
    Hydrolyses the peptide bond between two amino acids in dipeptide, allows for absorbtion of amino acid.

    Describe how bacteria divide ( 2 Marks)
    Binary Fission, organelles, plasmid and genetic material replicated and then grows and splits.

    How much drug should be given to the mice? (2 Marks)
    The dose given was /kg, so you must divide by 1000 and then multiply by 35 (the weight of the mouse) to get 0.75g.

    Explain how the bacterial resistance arised through natural selection and why two antibiotics should be used (2 marks)
    Random mutation of genes occurs, making one bacterium resistant to one of the antibiotics. If one antibiotic were to be used, then this bacterium would survive and reproduce by binary fission, creating a population of resistant baceria by passing on its resistant genes. If two antibiotics are used, it significantly reduces the risk of antibiotic resistance, as even if a bacterium develops resistance to one antibiotic, it will quickly be killed by the other one.

    Describe the role of phagocytosis in displaying antigens (~3 marks)
    Phagocyte engulfs and lysozymes bind to the vesicle. Hydrolytic enzymes are released, breaking it down. Then, the antigen makes its way to the cell surface membrane to be presented.

    Describe how presentation of an antigen leads to the secretion of antibodies (~3 marks)
    Phagocytes present the antigens, triggering helper T cells which activate B cells. The B cells divide by clonal selection, producing plasma cells which secrete specific monoclonal antibodies to the antigen.

    Why does the Viral protein lead to Rheumatoid Arthritis (2 Marks)
    Similar shape to collogan so antibody will form antigen-antibody complex and mark collogan for destruction, RA is auto immune.

    Suggest 3 environmental factors the scientists would control when growing the wild oat weed and the wheat plants (3 marks)
    Light intensity
    Humidity
    Temperature
    Soil mineral composition

    Evaluate the use of the 2,4-D herbicide on wheat and oat weed - NEEDS CLARIFYING (~3 marks)
    Potential answers:

    The herbicide was more effective on the wild oat weed, showing that it was good for use as a herbicide and stunted its growth. Therefore, there was more mineral availability for the wheat crop. However, there was an effect on the wheat plants, suggesting the herbicide may decrease the crop yield.

    There was only a difference of one, and the LSD value for that particular crop was much higher than 1, so I said that it was a statistically insignificant result and so could not be used either way, and that further testing was required to determine whether it actually had an effect or whether it was due to random chance, not that it had a slight effect on the wheat crop.

    Suggest how the student's scientific diagram could be improved (~2 marks)
    Draw continuous lines
    Do not use shading
    Cohesive labelling

    Compare and contrast how transmission electron microscopes and optical microscopes work, and their limitations and advantages (6 marks)
    Optical microscopes work by firing light at the cell, where it reflects, whereas TEMs fire electrons through the specimen.
    TEMs fire electrons in a vacuum so the sample must be dead, while optical microscopes can view living tissue
    TEMs are higher resolution - you can see small organelles because it has a shorter wavelength, whereas in the optical microscopes you can only see large organelles eg the nucleus.
    TEMs can go to 1,500,000x magnification, optical microscopes to 1,500x
    Optical microscopes produce colour images while TEM produces black and white

    Fill in the table: (2 marks?)
    Doman, kingdom, phylum, class, order, (family - already on the table).

    Which taxon do the scientists disagree on? (1 mark)
    Genus

    Why is mRNA different to pre-RNA? (2 marks)
    mRNA has already been spliced and therefore doesn't contain introns

    Which reaction does ATP Synthase catalyse? (1 mark)
    ADP + Pi -> ATP and H2O

    State 3 methods the scientists would use to determine the evolutionary relationship between the snakes (3 marks)
    DNA base sequence
    mRNA base sequence
    Amino acid sequence of the same protein

    A scientist wanted to investigate a link between the size of seeds and air pollution of one species of tree. He was given a large sample of seeds from the city and a large sample of seeds from the countryside. Describe and explain how he would collect and process his results (5 marks)
    Collection and Analysis of data:
    Two groups of seeds, 1 from city trees and 1 from countryside trees.
    Measure diameters of seeds for both groups
    Find mean diameter of each group of seeds
    Find SD for both groups.
    Conduct statistical t-test to check for significance between two means.
    Calculate degree of freedoms (n-1)
    Compare value from t-test to critical value in the statistical table.
    Will tell you if results are significant or not based on the comparison.
    Potential marks:
    Calculate volume of seeds (4/3 pi x r^3) so it's related to size?
    Mention overlap of SD to also look at significance?





    Offline

    5
    ReputationRep:
    (Original post by Amefish)
    Since I've seen a lot of people asking for the unofficial mark scheme, I thought: why not make a thread? Now, no-one's memory is absolutely perfect so we need to work together to remember the questions (and hopefully the answers). Thankfully, I remember the very first question (albeit not the actual wording of the question) but feel free to contribute your own and I'll stick it on the post.

    Granted, I don't have much to contribute right now but I'm sure as people join in, we'll build up a right good answer list!

    Ribosomes are made up of what molecules? (1 mark)
    Protein and rRNA
    I think the second question was how are ribosomes used to make a polypeptide.Do not include transcription in your answer
    • Community Assistant
    • Thread Starter
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by redwolf6504)
    I think the second question was how are ribosomes used to make a polypeptide.Do not include transcription in your answer
    Yep, it was! That threw me off at first because I thought it said 'do not include translation in your answer' :eek: do you think you know the answer? Mine was such a mess for that! And do you remember any other questions?
    Offline

    1
    ReputationRep:
    there was a six marker that went something along the lines of compare and contrast transmission electron microscopes and optical microscopes
    Offline

    1
    ReputationRep:
    a question on improvements to the student's scientific diagram
    I think the answer was something along the lines of : have continuous lines, not disjointed (if that even makes sense), and don't shade
    idek i probably failed that
    Offline

    14
    ReputationRep:
    i can post the paper in a bit paper but id rather focus on A2.
    Offline

    1
    ReputationRep:
    there was a question on evolutionary relationships
    and a table on levels of classification which we had to fill in
    a smaller question on what the scientists disagreed on, relating to the binomial naming system (i think it was to do with the genus?)

    im just quickly writing this all down before i forget
    Offline

    0
    ReputationRep:
    Why mrna is different to pre mRNA
    Offline

    1
    ReputationRep:
    Tick the box for the ATP Synthase question

    Describe the role of phagocytosis in displaying antigens

    Describe how presentation of an antigen leads to the secretion of antibodies

    State 3 methods the scientists would use to determine the evolutionary relationship between the snakes

    Explain the shape of the curves at 50°C and 60°C

    Suggest 3 variables the scientists would control

    Evaluate the use of the 2,4-D herbicide on wheat and oatcrop/weed
    Offline

    1
    ReputationRep:
    [QUOTE=Amefish;72117052]Since I've seen a lot of people asking for the unofficial mark scheme, I thought: why not make a thread? Now, no-one's memory is absolutely perfect so we need to work together to remember the questions (and hopefully the answers). Thankfully, I remember the very first question (albeit not the actual wording of the question) but feel free to contribute your own and I'll stick it on the post.

    Granted, I don't have much to contribute right now but I'm sure as people join in, we'll build up a right good answer list!

    Ribosomes are made up of what molecules? (1 mark)
    Protein and rRNA

    Describe how ribosomes are used to make polypeptides. Do not include transcription in your answer. (~3 marks)

    Suggest how the student's scientific diagram could be improved (~2 marks)
    Draw continuous lines
    Do not use shading
    Cohesive labelling

    Compare and contrast how transmission electron microscopes and optical microscopes work, and their limitations and advantages (6 marks)
    Optical microscopes work by firing light at the cell, whereas TEMs fire electrons.
    TEMs are higher resolution - you can see small organelles, whereas in the optical microscopes you can only see large organelles eg the nucleus.
    TEMs can go to 1,500,000x magnification, optical microscopes to 1,500x
    /QUOTE]

    TEMs fire a beam of electrons that travels through the specimen, while the specimen in optical microscopes reflect light
    TEMs fire electrons in a vacuum so the sample must be dead, while optical microscopes can view living tissue Optical microscopes have a lower resolution because light has a longer wavelength: électrons travel faster so have a shorter wavelength, so TEM has high resolution Optical microscopes produce colour images while TEM produces black and white

    Describe how ribosomes are used to make polypeptides. Do not include transcription in your answer. (~3 marks)

    mRNA travels out of the nucleus onto the RER where it slots into the groove between the unit and subunit of a ribosome As ribosome translates the mRNA, complementary tRNA anticodons deposit amino acids that are joined by peptide bonds, creating a polypeptide chain

    Also there was a question about, 'A scientists wanted to investigate a link between the size of seeds and air pollution of one species of tree. He was given a large sample of seeds from the city and a large sample of seeds from the countryside. Describe and explain how he would collect and process his results. (4marks)
    Offline

    4
    ReputationRep:
    I'm missing a couple questions, they might also be in the wrong order/mismatched but that's what I can remember.

    Question 1
    a) What two molecules are ribosomes made of? (1 Mark)
    RNA and Protein
    b) Describe the role of ribosomes in protein sythesis (do not write about translation. (3 Marks)
    tRNA anticodon attachment, amino acid peptide bond forms, forms chain etc
    c) DNA - mRNA base table (1 Mark)
    d) Base code of mRNA and pre-mRNA is different, explain why. (2 Marks)
    pre-mRNA has introns, mRNA goes through splicing so no introns

    Question 2
    a) Describe the structure of glycogen (2 marks)
    a-glucose with 1-4/1-6 so heavily branched and compact due to helical shape (it does helical up)
    b) Describe how glycogen is a good energy source in animals (2 marks)
    readily hydrolysed the glycosidic bonds to give off energy and to produce ATP following aerobic respiration
    c) What two adaptations does the cell membrane in the uterine lining have that makes it efficient for nutrient transport (2 marks)
    many protein carriers, thin membrane (??)
    d) Volume of each cell following 3 days of fertilisation (2 Marks)
    Number/128

    Question 3
    a) Explain the action of the H+/Na+ Pump (3 Marks)
    Both bind to seperate areas, ATP hydrolysis used to change protein shape to move Na+ against the gradient and then H+ moved out
    b) Explain all the scientists results (Why mass increased and P value meaning) (4 Marks)
    Mass increased because salt stayed high in gut so wp lowered, causign water to move in via osmis. P value of <0.05 meant that % due to chance was less than 5% so significant.
    c) Increased salt results in tissue fluid build up, explain why. (2 Marks)
    salt moves out b/c of hydrostatic but wp lower in tissue fluids, so cannot reenter. Lymphatic system cannot completely drain excess fluid

    Question 4
    a) Explain the 50 degree curve and the 60 degree curve (4 Marks)
    60 was b/c of denaturation as it hit 0 pretty fast. 50 not sure, but fast reaction rate means substrate used up so less protease at max activity. Denaturation may have occured but not completely as curve leveled off not reach 0
    b) Describe and explain the advantage of secreting extracellular proteins (2 marks)
    c) Describe the action of membrane bound dipeptidases and explain the advantage (2 marks)
    Hydrolyses the peptide bond between two amino acids in dipeptide, allows for absorbtion of amino acid.

    Question 5
    a) Describe how bacteria divide ( 2 Marks)
    Binary Fission, organelles, plasmid and genetic material replicated and then grows and splits.
    b) How much drug should be given to the mice? (2 Marks) 0.75g
    c) Surface area/uncertainty maths questions (2 Marks) 19.85mm^3 iirc, 18.5%
    d) explain how the bacterial resistance arised through natural selection and why two antibiotics should be used (3 marks) Usual natural selection answer, two should be used as liklihood of it being resistant to both is low so will wipe out bacteria.


    Question 6
    a) How does phagocytosis lead to antigen surface presentation (3 Marks)
    Engulfment via endocytosis, lysosome fuses to vesicle, hydrolytic enzymes, debris contains antigens and is presented.
    b) How does antigen surface presentation lead to antibody secretion (3 Marks)
    T-helper cell binds to antigen, activates B cell, B cell divides into Plasma cells that secrete antibody specifc to antigen T-H cell bound to.
    c) Why does the Viral protein lead to Rheumatoid Arthritis (2 Marks)
    Similar shape to collogan so antibody will form a-a complex and mark collogan for destruction, RA is auto immune.

    Question 7
    a) Describe three variables that the scientist would have controlled (2 marks)
    Light Intensity/Humidity/Soil Mineral Composition/Humidity/Temperature
    b) Does the data support the conlcusion (4 Marks)
    Yes, no lSD overlap. Shows that no effect on membrane for wheat but more ions leave for wild oats so membrane disrupted, loss of ions kills cells as no metabolic reagents.
    c)

    Question 8
    a) Describe what Classification X and Y show in terms of evolutionary relationships (2 marks)
    One was closely related where as the other had the same two species more distantly
    b) Fill in the taxon table (1 Mark) D-O F was filled in
    c) What Taxon were the scientists arguing over? (1 Mark) Genus
    d) Describe three ways the scientists determien genetic relationships (3 Marks) Base Sequence, Amino Acid Sequence and Immunoglobin/Cytochrome C comparison

    Question 9
    a) Describe and explain 3 adaptations of tracheal systems for efficient gas exchange (3 Marks)
    b) How does the gill in the larvae help it to be adapted to its behaviour (2 Marks) Counter current, max oxygen absorption for respiration as they actively hunt prey
    c) Something here, not entirely sure tbh
    d) Improve the scientific drawing (2 Marks) Continuous lines, no shading - straight line at base, labelling, magnification etc

    Questions 10
    a) Contrast principles and limitations of TEM and optical (6 Marks)
    b) Explain the appearance of W and Z (both sex daughter cells, one had 4 cells, one had 2) (4 Marks)
    c) Describe how the scientist should collect and process the data to see if there is a difference in seed size (5 Marks)
    Offline

    12
    ReputationRep:
    The very last question was 5 marks.

    Collection and Analysis of data:
    Two groups of seeds, 1 from city trees and 1 from countryside trees.
    Measure diameters of seeds for both groups
    Find mean diameter of each group of seeds
    Find SD for both groups.
    Conduct statistical t-test to check for significance between two means.
    Calculate degree of freedoms (n-1)
    Compare value from t-test to critical value in the statistical table.
    Will tell you if results are significant or not based on the comparison.

    Potential marks:
    Calculate volume of seeds (4/3 pi x r^3) so it's related to size?
    Mention overlap of SD to also look at significance?
    • Community Assistant
    • Thread Starter
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by DrNippleson)
    I'm missing a couple questions, they might also be in the wrong order/mismatched but that's what I can remember.
    Thanks for that! I'll get them put on.

    Does anyone have any answers for the questions? Every answer is welcome!
    Offline

    4
    ReputationRep:
    (Original post by Amefish)
    Thanks for that! I'll get them put on.

    Does anyone have any answers for the questions? Every answer is welcome!
    I'm adding the ones to mine now - should be up later
    Offline

    4
    ReputationRep:
    (Original post by DrNippleson)
    I'm missing a couple questions, they might also be in the wrong order/mismatched but that's what I can remember.

    Question 1
    a) What two molecules are ribosomes made of? (1 Mark)
    b) Describe the role of ribosomes in protein sythesis (do not write about translation. (3 Marks)
    c) DNA - mRNA base table (1 Mark)
    d) Base code of mRNA and pre-mRNA is different, explain why. (2 Marks)

    Question 2
    a) Describe the structure of glycogen (2 marks)
    b) Describe how glycogen is a good energy source in animals (2 marks)
    c) What two adaptations does the cell membrane in the uterine lining have that makes it efficient for nutrient transport (2 marks)
    d) Volume of each cell following 3 days of fertilisation (2 Marks)

    Question 3
    a) Explain the action of the H+/Na+ Pump (3 Marks)
    b) Explain all the scientists results (Why mass increased and P value meaning) (4 Marks)
    c) Increased salt results in tissue fluid build up, explain why. (2 Marks)

    Question 4
    a) Explain the 50 degree curve and the 60 degree curve (4 Marks)
    b) Describe and explain the advantage of secreting extracellular proteins (2 marks)
    c) Describe the action of membrane bound dipeptidases and explain the advantage (2 marks)

    Question 5
    a) Describe how bacteria divide ( 2 Marks)
    b) How much drug should be given to the mice? (2 Marks)
    c) Surface area/uncertainty maths questions (2 Marks)
    d) explain how the bacterial resistance arised through natural selection and why two antibiotics should be used (3 marks)


    Question 6
    a) How does phagocytosis lead to antigen surface presentation (3 Marks)
    b) How does antigen surface presentation lead to antibody secretion (3 Marks)
    c) Why does the Viral protein lead to Rheumatoid Arthritis (2 Marks)

    Question 7
    a) Describe three variables that the scientist would have controlled (2 marks)
    b) Does the data support the conlcusion (4 Marks)
    c)

    Question 8
    a) Describe what Classification X and Y show in terms of evolutionary relationships (2 marks)
    b) Fill in the taxon table (1 Mark)
    c) What Taxon were the scientists arguing over? (1 Mark)
    d) Describe three ways the scientists determien genetic relationships (3 Marks)

    Question 9
    a) Describe and explain 3 adaptations of tracheal systems for efficient gas exchange (3 Marks)
    b) How does the gill in the larvae help it to be adapted to its behaviour (2 Marks)
    c) Something here, not entirely sure tbh
    d) Improve the scientific drawing (2 Marks)

    Questions 10
    a) Contrast principles and limitations of TEM and optical (6 Marks)
    b) Explain the appearance of W and Z (both sex daughter cells, one had 4 cells, one had 2) (4 Marks)
    c) Describe how the scientist should collect and process the data to see if there is a difference in seed size (5 Marks)
    Wait so it actually is a pump?! I was just chatting a load of wham
    Offline

    4
    ReputationRep:
    (Original post by Luis99)
    Wait so it actually is a pump?! I was just chatting a load of wham
    It's an antiport, so it works in the same exact way as the Na+/k+ pump
    Offline

    1
    ReputationRep:
    (Original post by DrNippleson)
    I'm missing a couple questions, they might also be in the wrong order/mismatched but that's what I can remember.

    Question 1
    a) What two molecules are ribosomes made of? (1 Mark)
    b) Describe the role of ribosomes in protein sythesis (do not write about translation. (3 Marks)
    c) DNA - mRNA base table (1 Mark)
    d) Base code of mRNA and pre-mRNA is different, explain why. (2 Marks)

    Question 2
    a) Describe the structure of glycogen (2 marks)
    b) Describe how glycogen is a good energy source in animals (2 marks)
    c) What two adaptations does the cell membrane in the uterine lining have that makes it efficient for nutrient transport (2 marks)
    d) Volume of each cell following 3 days of fertilisation (2 Marks)

    Question 3
    a) Explain the action of the H+/Na+ Pump (3 Marks)
    b) Explain all the scientists results (Why mass increased and P value meaning) (4 Marks)
    c) Increased salt results in tissue fluid build up, explain why. (2 Marks)

    Question 4
    a) Explain the 50 degree curve and the 60 degree curve (4 Marks)
    b) Describe and explain the advantage of secreting extracellular proteins (2 marks)
    c) Describe the action of membrane bound dipeptidases and explain the advantage (2 marks)

    Question 5
    a) Describe how bacteria divide ( 2 Marks)
    b) How much drug should be given to the mice? (2 Marks)
    c) Surface area/uncertainty maths questions (2 Marks)
    d) explain how the bacterial resistance arised through natural selection and why two antibiotics should be used (3 marks)


    Question 6
    a) How does phagocytosis lead to antigen surface presentation (3 Marks)
    b) How does antigen surface presentation lead to antibody secretion (3 Marks)
    c) Why does the Viral protein lead to Rheumatoid Arthritis (2 Marks)

    Question 7
    a) Describe three variables that the scientist would have controlled (2 marks)
    b) Does the data support the conlcusion (4 Marks)
    c)

    Question 8
    a) Describe what Classification X and Y show in terms of evolutionary relationships (2 marks)
    b) Fill in the taxon table (1 Mark)
    c) What Taxon were the scientists arguing over? (1 Mark)
    d) Describe three ways the scientists determien genetic relationships (3 Marks)

    Question 9
    a) Describe and explain 3 adaptations of tracheal systems for efficient gas exchange (3 Marks)
    b) How does the gill in the larvae help it to be adapted to its behaviour (2 Marks)
    c) Something here, not entirely sure tbh
    d) Improve the scientific drawing (2 Marks)

    Questions 10
    a) Contrast principles and limitations of TEM and optical (6 Marks)
    b) Explain the appearance of W and Z (both sex daughter cells, one had 4 cells, one had 2) (4 Marks)
    c) Describe how the scientist should collect and process the data to see if there is a difference in seed size (5 Marks)
    Great! 😀 But I think the surface area/uncertainty question was to do with the larvae, and in its place was a question on the antibiotic affecting mice and not human enzymes. There was also something for a log graph calculating the percentage difference
    Offline

    9
    ReputationRep:
    Some of the q's/answers I can remember that I don't think have been answered here yet. They're in a random order and I'm not sure if all the answers are correct!

    Describe the structure of glycogen (2 marks)
    Contains alpha glucose, with 1,4 and 1,6 glycosidic bonds, and is also branched.

    Describe why glycogen is a good energy source for babies (2 marks)
    It's branched so is easily accessible in order for it to be hydrolysed for energy and converted into glucose. (Not too sure if that'd get you 2 marks - that's what I can remember)

    Describe how bacteria divide (2 marks)
    By binary fission, whereby the circular DNA and plasmids replicate (the plasmids sometimes replicate multiple times - DNA only once) and then divide into 2 cells.

    How much of the antibiotic should be given to the mice per day? (2 marks)
    0.75 mg.

    Explain why the number bases in pre-mRNA and mRNA are different. (2 marks)
    pre-mRNA contains introns, which are bases that do not code for amino acids. In mRNA these introns have been spliced out, so it only contains exons, decreasing the number of bases in it.

    Two adaptations that make the uterus cell membrane efficient in transporting substances. (2 marks)
    Thin cell membrane to allow a short diffusion pathway for substances, and a large surface area to increase the rate of diffusion.
    Offline

    4
    ReputationRep:
    (Original post by Adam7789)
    Great! 😀 But I think the surface area/uncertainty question was to do with the larvae, and in its place was a question on the antibiotic affecting mice and not human enzymes. There was also something for a log graph calculating the percentage difference
    haha, I did say they were mismatched rofl. My memory is only good to a point....
    Offline

    1
    ReputationRep:
    (Original post by Amefish)
    Since I've seen a lot of people asking for the unofficial mark scheme, I thought: why not make a thread? Now, no-one's memory is absolutely perfect so we need to work together to remember the questions (and hopefully the answers). Thankfully, I remember the very first question (albeit not the actual wording of the question) but feel free to contribute your own and I'll stick it on the post.

    Granted, I don't have much to contribute right now but I'm sure as people join in, we'll build up a right good answer list!

    Spoiler:
    Show







    Ribosomes are made up of what molecules? (1 mark)
    Protein and rRNA

    Describe how ribosomes are used to make polypeptides. Do not include transcription in your answer. (~3 marks)
    mRNA travels out of the nucleus onto the RER where it slots into the groove between the unit and subunit of a ribosome. As ribosome translates the mRNA, complementary tRNA anticodons deposit amino acids that are joined by peptide bonds, creating a polypeptide chain.

    Suggest how the student's scientific diagram could be improved (~2 marks)
    Draw continuous lines
    Do not use shading
    Cohesive labelling

    Compare and contrast how transmission electron microscopes and optical microscopes work, and their limitations and advantages (6 marks)
    Optical microscopes work by firing light at the cell, where it reflects, whereas TEMs fire electrons through the specimen.
    TEMs fire electrons in a vacuum so the sample must be dead, while optical microscopes can view living tissue
    TEMs are higher resolution - you can see small organelles because it has a shorter wavelength, whereas in the optical microscopes you can only see large organelles eg the nucleus.
    TEMs can go to 1,500,000x magnification, optical microscopes to 1,500x
    Optical microscopes produce colour images while TEM produces black and white

    Fill in the table: (2 marks?)
    Doman, kingdom, phylum, class, order, (family - already on the table).

    Which binomial name do the scientists disagree on? (1 mark)
    Genus

    Why is mRNA different to pre-RNA? (2 marks)
    mRNA has already been spliced and therefore doesn't contain introns

    Which reaction does ATP Synthase catalyse? (1 mark)
    ADP + Pi -> ATP and H2O

    Describe the role of phagocytosis in displaying antigens (~3 marks)

    Describe how presentation of an antigen leads to the secretion of antibodies (~3 marks)
    Phagocytes present the antigens, triggering helper T cells which activate B cells. The B cells divide by clonal selection, producing plasma cells which secrete specific monoclonal antibodies to the antigen.

    State 3 methods the scientists would use to determine the evolutionary relationship between the snakes (3 marks)
    DNA base sequence

    Suggest 3 environmental factors the scientists would control when growing the wild oat weed and the wheat plants (3 marks)
    Light intensity
    Humidity

    Evaluate the use of the 2,4-D herbicide on wheat and oat weed (~3 marks)
    The herbicide was more effective on the wild oat weed, showing that it was good for use as a herbicide and stunted its growth. However, there was an effect on the wheat plants, suggesting the herbicide may decrease the crop yield.

    Explain the shape of the curves at 50°C and 60°C
    60°C declined more rapidly due to the high amounts of heat energy causing the bonds to be broken, therefore changing the tertiary structure of the enzyme and meaning it no longer has a complementary active site to the substrate so is rendered ineffective. The same thing happens at 50°C, but more slowly as there is less heat energy to break the bonds between the amino acids.

    A scientist wanted to investigate a link between the size of seeds and air pollution of one species of tree. He was given a large sample of seeds from the city and a large sample of seeds from the countryside. Describe and explain how he would collect and process his results (5 marks)
    Collection and Analysis of data:
    Two groups of seeds, 1 from city trees and 1 from countryside trees.
    Measure diameters of seeds for both groups
    Find mean diameter of each group of seeds
    Find SD for both groups.
    Conduct statistical t-test to check for significance between two means.
    Calculate degree of freedoms (n-1)
    Compare value from t-test to critical value in the statistical table.
    Will tell you if results are significant or not based on the comparison.

    Potential marks:
    Calculate volume of seeds (4/3 pi x r^3) so it's related to size?
    Mention overlap of SD to also look at significance?

    For the question: State 3 methods the scientists would use to determine the evolutionary relationship between the snakes Question
    The 3 answers are:
    Compare DNA base sequence
    Compare mRNA base sequence
    Compare the amino acid sequence of the same protein

    I think that threw a lot of people off as it sneakily said in the question 'other genetic characteristics' so I'm unsure as to whether DNA Hybridisation or Immunological comparison will be accepted.

    However, the 3 that I've given are stated point blank in the specification.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: April 25, 2018
The home of Results and Clearing

2,934

people online now

1,567,000

students helped last year

University open days

  1. Sheffield Hallam University
    City Campus Undergraduate
    Tue, 21 Aug '18
  2. Bournemouth University
    Clearing Open Day Undergraduate
    Wed, 22 Aug '18
  3. University of Buckingham
    Postgraduate Open Evening Postgraduate
    Thu, 23 Aug '18
Poll
How are you feeling about GCSE results day?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.