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OCR Biology AS F211 May 2012

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    could someone tell me what aquaporins are ????
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    (Original post by Joey952)
    could someone tell me what aquaporins are ????
    Aquaporins are proteins embedded in the cell membrane that regulate the flow of water - you don't really need to know this for AS, as it is on the spec in F214 when you learn about osmoregulation (I'm an A2 student)
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    (Original post by Student-Andrew)
    A spirometer consist of a chamber filled with oxygen that floats on a tank of water. A person breaths from a disposable mouthpeice attached to a tube connected to the chamber of oxygen (medically graded). Breathing in takes oxygen away from the tank causing the lid of the tank to move down. Breathing out forces air into the tank causing it to move up.

    The movements are recorded on a data logger so a trace can be made

    This is like the procedure of how a Spirometer works, sorry if it still seems like jargon
    Thank you this made more sense than my text book. I just hope they don't ask us to calculate the tidal volume or anything like that.
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    ahh its tomorrow


    is it hard to gain a C or D in this exam?
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    (Original post by Unsworth)
    I think that would get one mark. Water is never part of active transport to my understanding.

    The mark would be 1. through channel proteins and 2. water can simply move across the membrane by osmosis as it is permeable to water.
    Actually, the phospholipid bilayer is impermeable to water (due to the hydrophobic lipid tails), it's only permeable to small, non-polar molecules such as carbon dioxide and oxygen. So really there's only one route through the cell surface membrane and that's through channel proteins
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    (Original post by skylight17)
    Aquaporins are proteins embedded in the cell membrane that regulate the flow of water - you don't really need to know this for AS, as it is on the spec in F214 when you learn about osmoregulation (I'm an A2 student)
    Yep was just going to write that. Are you resitting f211 aswell. It was more than a year since we covered the syllabus in class
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    (Original post by Joey952)
    could someone tell me what aquaporins are ????
    An a aquaporin is a protein in the membrane which is permeable to water, think of it like a channel protein made specifically for water
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    and the jan exam had nothing on heart & mitosis im sure that will come up !
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    (Original post by aisha302)
    ahh its tomorrow


    is it hard to gain a C or D in this exam?
    The grade boundaries are quite high but don't let that faze you, just do your best
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    1. State 3 roles of membranes inside cells - 3 marks

    2. Outline how vesicles are moved from one organelle to another - 2 marks

    3. Why is it important that products of photosynthesis can be moved in both directions through sieve tubes? 1 mark
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    (Original post by Jamie66)
    Actually, the phospholipid bilayer is impermeable to water (due to the hydrophobic lipid tails), it's only permeable to small, non-polar molecules such as carbon dioxide and oxygen. So really there's only one route through the cell surface membrane and that's through channel proteins
    Some water molecules can pass through even though water is polar.
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    (Original post by sumsum123)
    Correct Define homologous chromosomes.
    SOne chromosomes have the same genes at the same loci, these are homologous chromosomes
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    (Original post by Unsworth)
    1. State 3 roles of membranes inside cells - 3 marks

    2. Outline how vesicles are moved from one organelle to another - 2 marks

    3. Why is it important that products of photosynthesis can be moved in both directions through sieve tubes? 1 mark
    1. forms seperate organelles.
    controls what substances enters and exits organelles
    -
    2. the cytoskeleton is made out of micrrotubule which provides a track for vesicle.
    it uses ATP to allow movement

    3. so that sucrose can reach all parts of the plant and can be stored so that it can be used for respiration (?)
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    (Original post by Jamie66)
    Actually, the phospholipid bilayer is impermeable to water (due to the hydrophobic lipid tails), it's only permeable to small, non-polar molecules such as carbon dioxide and oxygen. So really there's only one route through the cell surface membrane and that's through channel proteins
    No it is partially permeable. Water molecules can pass through the phospholipd bilayer regardless that it's hydrophobic and what not. So even though water molecules are polar, they are still able to pass through the bilayer.
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    (Original post by PrettyLittleLiars)
    Yep was just going to write that. Are you resitting f211 aswell. It was more than a year since we covered the syllabus in class
    I'm doing it for a third time! (don't laugh ) - I'm aiming to get full marks so I don't have to do as well on F215. At the moment I need 124/150 for an A, but I could get it down to 101/150.

    How about you?

    P.S. That is what happened to me in Jan (my UMS only went up by 4!), as the F211 material wasn't very prominent in my mind and I thought I could manage it without doing much revision... I was wrong lol
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    (Original post by Unsworth)
    No it is partially permeable. Water molecules can pass through the phospholipd bilayer regardless that it's hydrophobic and what not. So even though water molecules are polar, they are still able to pass through the bilayer.
    I hate to say that you are wrong...

    polar / ionic ;
    cannot pass through , phospholipid layer / hydrophobic regions ;
    use , protein channels / protein carriers / transport proteins ;
    (protein channels with) hydrophilic , lining / channel / core ; (3 max)
    DO NOT CREDIT water-soluble (in Q)
    CREDIT impermeable to vitamin B1 / water
    CREDIT transmembrane / intrinsic protein
    DO NOT CREDIT aquaporin
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    does anybody have any clues of what might come up? i think heart & mitosis will......
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    (Original post by Unsworth)
    3. Why is it important that products of photosynthesis can be moved in both directions through sieve tubes?
    Roots cannot obtain sugars from the soil so rely on the phloem to transport it to them from the leaves, other cells use it for metabolic activites as well as storage by converting it into starch,

    Tricky question!!
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    (Original post by Jamie66)
    Actually, the phospholipid bilayer is impermeable to water (due to the hydrophobic lipid tails), it's only permeable to small, non-polar molecules such as carbon dioxide and oxygen. So really there's only one route through the cell surface membrane and that's through channel proteins
    See above - just reinforced your point about water not being able to pass through the membrane due to it's polar nature.
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    (Original post by skylight17)
    I hate to say that you are wrong...

    polar / ionic ;
    cannot pass through , phospholipid layer / hydrophobic regions ;
    use , protein channels / protein carriers / transport proteins ;
    (protein channels with) hydrophilic , lining / channel / core ; (3 max)
    DO NOT CREDIT water-soluble (in Q)
    CREDIT impermeable to vitamin B1 / water
    CREDIT transmembrane / intrinsic protein
    DO NOT CREDIT aquaporin
    Which paper is this from?
Updated: May 23, 2012
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