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    Question: A steep diffusion gradient must be by ventilating the lungs. This refreshes air in the air sacs. Describe and explain another way in which a steep diffusion gradient is maintained in the lungs other than this.

    My answer:
    There is a constant supply if blood from the body which has little oxygen and a lot of carbon dioxide this means oxygen which is a high concentration inside the alveoli can diffuse down the concentration gradient into the hemoglobin. And carbon dioxide diffuses into the air sacs down the concentration gradient.

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    I am not sure if what I would have said would get the marks. How strictly do examiners have to follow what is on the markscheme? thanks
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    Probably not. Your language is a bit scrappy - try and refine what you're trying to say. That is, instead of saying that the oxygen diffuses into the haemoglobin, use combines with, or something similar.
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    (Original post by mattmattmatt)
    Probably not. Your language is a bit scrappy - try and refine what you're trying to say. That is, instead of saying that the oxygen diffuses into the haemoglobin, use combines with, or something similar.
    clearly my answer shows I have competent knowledge

    this is why I hate biology
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    I'm unsure what board you're with but if I were answering the question, I'd say: A steep concentration gradient is maintained by the constant movement of oxygenated blood through the capillaries, away from the alveoli.

    As the above poster has said I don't believe that you'd get the mark. Although I think that examiner's partially use their own discernment, I believe that the mark scheme has to be followed strictly. Regarding your question, have you considered asking your teacher?
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    I don't think it would - whilst you will get credit even for the most clumsily expressed (and correct) answers, you didn't really answer the question, you just described what happens in the lungs. But yeah, you clearly have good knowledge, so it shouldn't be hard to get a more concrete answer
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    Like the others, I think your wording is what didn't help you out in this question - which exam board?
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    (Original post by Sparticon)
    I don't think it would - whilst you will get credit even for the most clumsily expressed (and correct) answers, you didn't really answer the question, you just described what happens in the lungs. But yeah, you clearly have good knowledge, so it shouldn't be hard to get a more concrete answer
    This is my problem with biology. I just don't know how I am going to put down exactly what they want in the mark scheme in the real exam in a question I have never seen before. I know the content inside out I just cannot apply it in a coherent manner that's going to get me the marks
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    (Original post by hskjlclcn)
    Like the others, I think your wording is what didn't help you out in this question - which exam board?
    OCR
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    (Original post by upthegunners)
    OCR
    Yeah...you definitely wouldn't get a mark.
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    (Original post by slacker07906)
    Yeah...you definitely wouldn't get a mark.
    Such a tough board

    your answers nearly have to be word perfect in order to get the marks
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    This is my problem with english :P Biology should be much easier if you remember some key phrases which the exam board like to see - ie xxx for validity of results, xxx for reliability of results, structure is related to function, control acts as a comparison with the experiment etc.

    Remember that the markers will try and give you marks when they can, it even says at the start of their marking schemes that their goal is to reward good biology and not penalise bad expression or try to find mistakes in an answer; so if in doubt try to cover all your bases by writing a longer answer (but be careful with timing) and try and look at what the key words of the question, ie Explain, show, suggest, state all have a generic answer type, and if you can crack that then you are half way to an A!

    And finally, play to your strengths: if you aren't so good at questions like the one above, then don't let them panic you, leave them and come back and then go back and try to make sure you have written something you could imagine being in the marking scheme.
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    (Original post by upthegunners)
    Such a tough board

    your answers nearly have to be word perfect in order to get the marks
    I know...trust me. OCR were by far the worst exam board during my A Levels. I had to sit one of my exams 3 times to get an A because I obviously knew the stuff but wasn't using the precise wording.
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    It doesn't matter which exam board it is, if you got the answer right then they'll give you the marks for it. You weren't very specific with your wording, for example "There is a constant supply if blood from the body which has little oxygen and a lot of carbon dioxide" is a bit long winded, when you could've just simply said blood in the pulmonary arteries is deoxygenated (which is not true, it will still contain some oxygen, but at A-level it's acceptable) contains little oxygen and excess CO2. Also, it would probably be better mentioning that O2 diffuses into the capillaries of the lungs from the alveoli, instead of the haemoglobin.

    You'd definitely get one mark for mentioning that the O2 and CO2 diffuse along a concentration gradient. Not sure about the other though.
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    You need to talk about higher levels in X than Y, NOT "this has high levels and this has low levels"
 
 
 
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