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    (Original post by AortaStudyMore)
    Yh, 2 measuring tapes at right angles and a random number generator to calculate coordinates will allow you to remove the bias
    Thankyou

    Btw Do you take physics or maths at medical college../
    I mean you've a choice right??
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    (Original post by Aimen.)
    Thankyou

    Btw Do you take physics or maths at medical college../
    I mean you've a choice right??
    Haha no, we don't get taught any of that and we don't have a choice, it's not natural sciences :P I did do maths at A-level and physics up to AS level though
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    (Original post by AortaStudyMore)
    Haha no, we don't get taught any of that and we don't have a choice, it's not natural sciences :P I did do maths at A-level and physics up to AS level though
    nahh i don't need help with that.. i just wanted info. cz ill be joining a medical school this year. and feel nervous
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    (Original post by Aimen.)
    nahh i don't need help with that.. i just wanted info. cz ill be joining a medical school this year. and feel nervous
    Ah right nice! Which one? Yh none of the UK medical schools will make you do physics or maths or even much chemistry, they teach you what you need to know to become a doctor and you do exams and that's it.
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    (Original post by AortaStudyMore)
    Ah right nice! Which one? Yh none of the UK medical schools will make you do physics or maths or even much chemistry, they teach you what you need to know to become a doctor and you do exams and that's it.
    Not really sure if i'm getting into a college in uk :/
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    (Original post by AortaStudyMore)
    Hey everyone, I am a medical student who doesn't really have time to do any proper, paid tutoring, however I am interested in teaching and helping people in general. I have tutored before, so if anyone is stuck on any GCSE/AS/A2 biology (or chemistry too for that matter) then feel free to ask and I'll help. Also if anyone has any questions about applying to medical school then I can help there too as I was in that position only last year, so it's fresh in my mind. I got 4 A's at AS and 3 A*s at A2 (bio, chem, maths, all above 95%)
    How much do you charge?

    I could use some help with acids, bases and buffers in Unit 4
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    (Original post by AngryRedhead)
    How much do you charge?

    I could use some help with acids, bases and buffers in Unit 4
    £100/hr. I joke, I don't charge, I do it for fun on here, just ask me anything and I'll get back to you asap... for free :P
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    (Original post by Aimen.)
    Not really sure if i'm getting into a college in uk :/
    Well that's not really a problem, where are you from/where are you going to study?
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    (Original post by AortaStudyMore)
    £100/hr. I joke, I don't charge, I do it for fun on here, just ask me anything and I'll get back to you asap... for free :P
    Hi there. This may be a big list of things to go over but Im sure AS Biology is a piece of cake to you xD.
    -Could you go over the process of protein synthesis and the role of mRNA and tRNA.
    -The immune response and role of interleukins and B and T Cells.
    -Counter current flow in fish.
    I would greatly appreciate it if you could over these. I'm also doing chem and Physics so could u maybe recommend some revision sites as I'm aiming for your grades at AS aswel as aiming to apply for Medicine.
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    Hi,

    Could you please explain the following EMPA terms to me:

    *Qualitative data
    *Quantitative data
    *Subjective


    Also some question on the benedicts test.

    How long do we heat the solution for ?

    Why do we use the same amount of Benedicts solution in each sample ? (is it acidic? to make it a fair test?)

    And also why can't we use the benedict test to test for a dissacharide.

    Thanks
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    (Original post by Logic4Life)
    Hi there. This may be a big list of things to go over but Im sure AS Biology is a piece of cake to you xD.
    -Could you go over the process of protein synthesis and the role of mRNA and tRNA.
    -The immune response and role of interleukins and B and T Cells.
    -Counter current flow in fish.
    I would greatly appreciate it if you could over these. I'm also doing chem and Physics so could u maybe recommend some revision sites as I'm aiming for your grades at AS aswel as aiming to apply for Medicine.
    Hey, good choice of university subject :P I can't remember quite how much detail you need at AS regarding these things, because I've been taught a lot about protein synthesis and immunology (nothing about fish though haha), so I'll go over what I think should be adequate for AS.

    So, protein synthesis, let's start with DNA. DNA is made of 2 strands, one of them is called the sense strand and one of them is called the antisense strand. The sense strand contains the same base sequence as the mRNA that is transcribed, however, all the T's are replaced with U's. Now, as we know, bases bond with complementary bases, i.e. A pairs with T or U and G pairs with C. This means that the mRNA must be formed using the antisense strand if it is going to get the same base sequence as the sense strand. Let me show this visually

    DNA
    TCGATATTC (Antisense strand)
    AGCTATAAG (Sense strand)

    Transcription
    TCGATATTC (Antisense strand)
    AGAUAUAAG (mRNA)

    What we can see here is that the sequence of bases in mRNA = the sequence of bases in the sense strand (with T's replaced with U's). We can also see that the mRNA has 3 codons, AGA, UAU and AAG. Codons technically only refer to the triplets on mRNA rather than the triplets on the sense DNA strand.

    Anyway, that's the process of transcription, which is carried out by RNA polymerase II. It is worth noting that the mRNA formed is not translated directly, it needs to undergo splicing. This is because a gene on DNA is made up of exons (which code for protein) and introns (which don't code for protein). These introns must be cut out or else you won't get a functioning protein. If you're interested in learning some more details stuff, then here are some extra cheeky facts, introns are cut out by snRNPs, which stands for small nuclear ribonucleoproteins, and also, before mRNA can be translated, it must have a couple of things added to it, these include a 7-methylguanlyate cap and a poly-adenosine tail. Anyway, you don't need to know that, I thought you might just be interested.

    Right, so the spliced mRNA enters the cytoplasm, and comes across a ribosome, the ribosome slides down the mRNA until it comes in contact with AUG, the start codon. This is where tRNA gets involved, tRNA is a clover-shaped RNA molecule, on one end it has an anticodon, which contains the complementary bases to the codon, and on the other end is an amino acid. In the case of AUG, the anticodon would be UAC and the amino acid would be methionine. Once the methionine tRNA is bound, protein translation begins, so what happens is another tRNA molecule carrying an amino acid comes a long and binds to the next codon after AUG, peptidyl transferase then forms a peptide bond between the 2 amino acids, once it has done this, the first tRNA molecule leaves, and the ribosome slides down, once it has done this, another tRNA molecule comes a long with a amino acid, and the process repeats until you come across a stop codon. Once a stop codon is reached, the ribosomes dissociate and the protein goes off to wherever it needs to go.

    Phew, I'll try not to write as much for the next 2 answers...

    Okay so I could literally write an essay on T cells and B cells and their interaction, but I'll try and keep it short. Basically, you have an antigen in tissue, this can either be on a host cell or on a bacteria. What happens is phagocytes endocytose the antigen and present it on their surface. A T-cell with a specific complementary receptor then comes a long and binds to the antigen, thus activating it into a helper T cell. The helper T cell will then look for a B cell that has also endocytosed the same antigen, this B cell will also be presenting the antigen on its surface. The T cell binds to this antigen and release interleukins too. Interleukins are a type of cytokine, cytokines are just molecules released by immune cells that have some kind of effect on another immune cell, in this case, the combination of the B cell binding to the T cell and the release of interleukins leads to the activation of the B cell. The B cells then undergo clonal expansion, where they form memory B cells and plasma cells by mitosis. B cells then release antibodies, which can agglutinate, opsonise and neutralise pathogens, while T helper cells activate other cells of the immune system and T killer cells specifically kill cells infected by viruses or cancer cells. The immune response is a huge thing to try and explain, that was a very very brief overview, but it should hopefully give you a slightly better understanding of what is going on.

    Right, finally, the thing i know least, basically, in fish, the blood flow through the gills is in the opposite direction to the flow of water over the gills. There is a fundamental reason for this. If the blood and water flowed in the same direction, then eventually the oxygen concentrations in both would equilibriate, and this isn't very efficient. I'll show you what I mean:

    ---------> Flow of water + blood
    10-9-8-7-6-5-5-5-5-5 (Oxygen conc in water)
    0-1-2-3-4-5-5-5-5-5 (Oxygen conc in blood)
    As we can see, this is only going to saturate the blood by 50% = Not good

    But when you have countercurrent flow, you get a concentration gradient for the entire time that blood and water are flowing through the gills, i.e.

    ---------> Flow of water
    10-9-8-7-6-5-4-3-2-1 (Oxygen conc in water)
    9-8-7-6-5-4-3-2-1-0 (Oxygen conc in blood)
    <---------- Flow of blood

    This is much more efficient. The reason this works is because you want the regions of the blood and water that are low in oxygen to be next to eachother, so that you don't get that equilibrium establishing. You may think that if the low oxygen water meets the low oxygen blood then there still won't be much exchange, but because the water has a higher oxygen concentration then the blood, then there is always going to be a diffusion gradient.

    I don't know how well I explained that last one, it's a tricky concept, but I'm tired haha. Enjoy reading all that, I'm off to bed!
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    (Original post by Spov99)
    Hi,

    Could you please explain the following EMPA terms to me:

    *Qualitative data
    *Quantitative data
    *Subjective


    Also some question on the benedicts test.

    How long do we heat the solution for ?

    Why do we use the same amount of Benedicts solution in each sample ? (is it acidic? to make it a fair test?)

    And also why can't we use the benedict test to test for a dissacharide.

    Thanks
    Qualitative data is data is descriptive, such as colour of a solution or something.
    Quantative data is date that is numerical, such as someone's height.
    Subjective data is data that has been described to you by someone else, such as how severe a feeling of pain is.

    I honestly don't know how long you heat the solution for :P You'll have to look in a textbook or something. As for why you would use the same amount of benedict's reagent, I would assume it would be to make it a fair test or something yh. And benedict's test cannot be used to test for some disaccharides if they're not reducing sugars. Benedict's reagent works by being reduced by the reducing sugar, you start off with Cu^2+ which is then reduced to Cu+. If the disaccharide doesn't have a aldehyde or ketone group then it won't reduce the benedict's reagent.

    I feel that might be a bit too much of a complicated answer for what you need, I can't remember what level of detail you needed at AS, maybe best if you ask a teacher or read a textbook!
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    What is the difference between a benedict's and Fehling's reagent ?

    And if we're given two indicators, the two of them lie within the vertical section of pH curve, which one is better to choose, if we say one's pH colour change is below the equivalence point and one's beyond the equivalence point ?

    How do an acidic buffer solution form, I know from a week acid and its salt but I can't understand the dissociation equations accompanied with it?

    Sorry for asking a lot of questions
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    (Original post by AortaStudyMore)
    Well that's not really a problem, where are you from/where are you going to study?
    Applied to a few colleges in Dubai.. Donno what's gonna happen with that! Depends on my sat score.. If i get a perfect 2400 dad might lemme go to uk

    Btw do you have some helping material for sat 2 aswll?

    I need to understand action potentials and biomes better.. :/
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    (Original post by PlayerBB)
    What is the difference between a benedict's and Fehling's reagent ?

    And if we're given two indicators, the two of them lie within the vertical section of pH curve, which one is better to choose, if we say one's pH colour change is below the equivalence point and one's beyond the equivalence point ?

    How do an acidic buffer solution form, I know from a week acid and its salt but I can't understand the dissociation equations accompanied with it?

    Sorry for asking a lot of questions
    Posted from TSR Mobile
    I believe the acids they're made up of are different.. Benedict has citric acid and Fehlings has tartaric acid.. but that doesn't matter in A2 unit 5 .. as in all we should know is they both form red ppt of Cu2O with aldehydes..
    About indicators i believe the one whose Pka value is closer to equivalence point is better

    And the buffer is unclear to me aswell xD
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    AortaStudyMore could you please tell me the whole process of recrystallisation in chem A2..
    like step wise?
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    (Original post by AortaStudyMore)
    Hey, good choice of university subject :P I can't remember quite how much detail you need at AS regarding these things, because I've been taught a lot about protein synthesis and immunology (nothing about fish though haha), so I'll go over what I think should be adequate for AS.

    So, protein synthesis, let's start with DNA. DNA is made of 2 strands, one of them is called the sense strand and one of them is called the antisense strand. The sense strand contains the same base sequence as the mRNA that is transcribed, however, all the T's are replaced with U's. Now, as we know, bases bond with complementary bases, i.e. A pairs with T or U and G pairs with C. This means that the mRNA must be formed using the antisense strand if it is going to get the same base sequence as the sense strand. Let me show this visually

    DNA
    TCGATATTC (Antisense strand)
    AGCTATAAG (Sense strand)

    Transcription
    TCGATATTC (Antisense strand)
    AGAUAUAAG (mRNA)

    What we can see here is that the sequence of bases in mRNA = the sequence of bases in the sense strand (with T's replaced with U's). We can also see that the mRNA has 3 codons, AGA, UAU and AAG. Codons technically only refer to the triplets on mRNA rather than the triplets on the sense DNA strand.

    Anyway, that's the process of transcription, which is carried out by RNA polymerase II. It is worth noting that the mRNA formed is not translated directly, it needs to undergo splicing. This is because a gene on DNA is made up of exons (which code for protein) and introns (which don't code for protein). These introns must be cut out or else you won't get a functioning protein. If you're interested in learning some more details stuff, then here are some extra cheeky facts, introns are cut out by snRNPs, which stands for small nuclear ribonucleoproteins, and also, before mRNA can be translated, it must have a couple of things added to it, these include a 7-methylguanlyate cap and a poly-adenosine tail. Anyway, you don't need to know that, I thought you might just be interested.

    Right, so the spliced mRNA enters the cytoplasm, and comes across a ribosome, the ribosome slides down the mRNA until it comes in contact with AUG, the start codon. This is where tRNA gets involved, tRNA is a clover-shaped RNA molecule, on one end it has an anticodon, which contains the complementary bases to the codon, and on the other end is an amino acid. In the case of AUG, the anticodon would be UAC and the amino acid would be methionine. Once the methionine tRNA is bound, protein translation begins, so what happens is another tRNA molecule carrying an amino acid comes a long and binds to the next codon after AUG, peptidyl transferase then forms a peptide bond between the 2 amino acids, once it has done this, the first tRNA molecule leaves, and the ribosome slides down, once it has done this, another tRNA molecule comes a long with a amino acid, and the process repeats until you come across a stop codon. Once a stop codon is reached, the ribosomes dissociate and the protein goes off to wherever it needs to go.

    Phew, I'll try not to write as much for the next 2 answers...

    Okay so I could literally write an essay on T cells and B cells and their interaction, but I'll try and keep it short. Basically, you have an antigen in tissue, this can either be on a host cell or on a bacteria. What happens is phagocytes endocytose the antigen and present it on their surface. A T-cell with a specific complementary receptor then comes a long and binds to the antigen, thus activating it into a helper T cell. The helper T cell will then look for a B cell that has also endocytosed the same antigen, this B cell will also be presenting the antigen on its surface. The T cell binds to this antigen and release interleukins too. Interleukins are a type of cytokine, cytokines are just molecules released by immune cells that have some kind of effect on another immune cell, in this case, the combination of the B cell binding to the T cell and the release of interleukins leads to the activation of the B cell. The B cells then undergo clonal expansion, where they form memory B cells and plasma cells by mitosis. B cells then release antibodies, which can agglutinate, opsonise and neutralise pathogens, while T helper cells activate other cells of the immune system and T killer cells specifically kill cells infected by viruses or cancer cells. The immune response is a huge thing to try and explain, that was a very very brief overview, but it should hopefully give you a slightly better understanding of what is going on.

    Right, finally, the thing i know least, basically, in fish, the blood flow through the gills is in the opposite direction to the flow of water over the gills. There is a fundamental reason for this. If the blood and water flowed in the same direction, then eventually the oxygen concentrations in both would equilibriate, and this isn't very efficient. I'll show you what I mean:

    ---------> Flow of water + blood
    10-9-8-7-6-5-5-5-5-5 (Oxygen conc in water)
    0-1-2-3-4-5-5-5-5-5 (Oxygen conc in blood)
    As we can see, this is only going to saturate the blood by 50% = Not good

    But when you have countercurrent flow, you get a concentration gradient for the entire time that blood and water are flowing through the gills, i.e.

    ---------> Flow of water
    10-9-8-7-6-5-4-3-2-1 (Oxygen conc in water)
    9-8-7-6-5-4-3-2-1-0 (Oxygen conc in blood)
    <---------- Flow of blood

    This is much more efficient. The reason this works is because you want the regions of the blood and water that are low in oxygen to be next to eachother, so that you don't get that equilibrium establishing. You may think that if the low oxygen water meets the low oxygen blood then there still won't be much exchange, but because the water has a higher oxygen concentration then the blood, then there is always going to be a diffusion gradient. .

    I don't know how well I explained that last one, it's a tricky concept, but I'm tired haha. Enjoy reading all that, I'm off to bed!
    Wow thank you so much for this it helped a lot although the stuff on protein synthesis is a lot more complicated than anything we have done at AS, never heard of sense strands xD
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    (Original post by Aimen.)
    I believe the acids they're made up of are different.. Benedict has citric acid and Fehlings has tartaric acid.. but that doesn't matter in A2 unit 5 .. as in all we should know is they both form red ppt of Cu2O with aldehydes..
    About indicators i believe the one whose Pka value is closer to equivalence point is better

    And the buffer is unclear to me aswell xD
    Yeah, I have found the difference for Benedict's and Fehling's, for Fehling's,it consists of complexed Cu2+ ions with tartrate ions dissolved in NaOH while Benedict's consists of complexed Cu2+ ions with citrate ions dissolved in CaCO3.

    I guess you're right about indicators...

    so it's now one thing that is confusing, buffers....
    Spoiler:
    Show
    This topic is the one I struggle at it the most, I don't know why though :/
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    Name:  stp.PNG
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    Isn't standard temp supposed to be 25 degree celcius rather than 0 degree celcius?
    I'm confused cuz i see different stuff everywhere!
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    (Original post by AortaStudyMore)
    Hey everyone, I am a medical student who doesn't really have time to do any proper, paid tutoring, however I am interested in teaching and helping people in general. I have tutored before, so if anyone is stuck on any GCSE/AS/A2 biology (or chemistry too for that matter) then feel free to ask and I'll help. Also if anyone has any questions about applying to medical school then I can help there too as I was in that position only last year, so it's fresh in my mind. I got 4 A's at AS and 3 A*s at A2 (bio, chem, maths, all above 95%)
    Apart from the application of stereoisomers for drugs, how is chemistry relevant for medicine?
 
 
 
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