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Cholesterol in the phospholipid bilayer? watch

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    Hi, I was just casually reading over my notes, and then I was trying to list the components of the phospholipid bilayer, and their uses. So I listed:

    Glycoproteins/glycolipids- cell recognition (do we need to differentiate between the two, not as their biological components, but their uses?)

    Channel protein - To allow insoluble substances to travel across the membrane with the help of a carrier protein.

    Proteins - Use?

    Cholesterol - Use?

    I was a bit stuck for protein and cholesterol. I remember in class that the teacher mentioned that with more cholesterol, it makes more kinks in the fatty acid tails (or something like that), but I can't remember what the effect of more cholesterol would be, i.e. more fluid?

    I'd be grateful if someone could check if my explanations for channel proteins and glycoprotein/lipid were accurate and whether I missed anything. And also could you explain the use of protein/cholesterol (or why they are there) and if there is more cholesterol, what difference does that make?

    I'm doing AS Edexcel SNAB Biology by the way Thanks!
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    I think

    The permeable membrane is fluid (fluid mosaic model) this fluidity can allow unwanted substances and ions to move through the membrane, so cholesterol is found inbetween the phospholipids, that aids in the prevention of molecules freely moving accross the selectively permeable membrane.

    Proteins have a wide array of functions, usually you find globular proteins (enzymes) attached to the cell membrane that catalyse reactions

    Though i believe this is correct pls dont quote me on it dont wanna be giving ya bad advise. If anyone else can improve on this pls feel free
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    Cholesterol gives the membrane mechanical stability
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    (Original post by pheonix65)
    I think

    The permeable membrane is fluid (fluid mosaic model) this fluidity can allow unwanted substances and ions to move through the membrane, so cholesterol is found inbetween the phospholipids, that aids in the prevention of molecules freely moving accross the selectively permeable membrane.

    Proteins have a wide array of functions, usually you find globular proteins (enzymes) attached to the cell membrane that catalyse reactions

    Though i believe this is correct pls dont quote me on it dont wanna be giving ya bad advise. If anyone else can improve on this pls feel free
    I'm not sure about your point on the fluidity, as there are fatty acid tails inwards, then that would prevent insoluble substances from passing through anyway? I thought it was structural, but didn't know why.

    Ah, that makes sense with the proteins bit. Are you doing A level as well?

    (Original post by crazyangelg)
    Cholesterol gives the membrane mechanical stability
    How so?
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    (Original post by MedicalMayhem)
    How so?
    It controls the fluidity of the bilayer
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    did sum research ya gottae love wikipedia lol

    http://en.wikipedia.org/wiki/Cholesterol

    It is an essential structural component of mammalian cell membranes and is required to establish proper membrane permeability and fluidity
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    Did sum research for ya, ya gottae love wikipedia

    It is an essential structural component of mammalian cell membranes and is required to establish proper membrane permeability and fluidity
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    (Original post by Med_Geek)
    It controls the fluidity of the bilayer
    Ah okay, so more cholesterol in the bilayer would mean that it is less fluid? And might seem like a stupid question, but why is it important to control the fluidity of the bilayer?

    Also, though I know that the bilayer is fluid, if I asked "why is the bilayer fluid", how would you explain that? As all I know is the structure and how the fatty acid tails point to the inside of the membrane, but this doesn't explain why the bilayer is fluid though?
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    (Original post by pheonix65)
    Did sum research for ya, ya gottae love wikipedia

    It is an essential structural component of mammalian cell membranes and is required to establish proper membrane permeability and fluidity
    Ah thanks, "proper membrane permeability"? What exactly does this mean? :confused:
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    (Original post by MedicalMayhem)



    How so?
    by binding to polar heads and non-polar tails of phospholipids
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    Membrane packing
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    (Original post by MedicalMayhem)
    Ah okay, so more cholesterol in the bilayer would mean that it is less fluid? And might seem like a stupid question, but why is it important to control the fluidity of the bilayer?

    Also, though I know that the bilayer is fluid, if I asked "why is the bilayer fluid", how would you explain that? As all I know is the structure and how the fatty acid tails point to the inside of the membrane, but this doesn't explain why the bilayer is fluid though?
    Cholesterol causes kinks in the phospholipid tails the membrane fluidity is a result of these kinks affecting how closely the phospholipids pack together. IF there is to much fluidity in the membrane ions and substances can find ways to move across the membrane.
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    (Original post by MedicalMayhem)
    I'm not sure about your point on the fluidity, as there are fatty acid tails inwards, then that would prevent insoluble substances from passing through anyway? I thought it was structural, but didn't know why.

    Ah, that makes sense with the proteins bit. Are you doing A level as well?



    How so?
    Just doing my access course, done cell biology and just about to hand in ma biochemistry assignment
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    (Original post by pheonix65)
    Cholesterol causes kinks in the phospholipid tails the membrane fluidity is a result of these kinks affecting how closely the phospholipids pack together. IF there is to much fluidity in the membrane ions and substances can find ways to move across the membrane.
    So kinks in the fatty acid tails means they are less densely packed? But you didn't answer why/how the kinks affect fluidity?

    So am I right in thinking, more cholesterol = more kinks = less fluid?

    I don't understand the relationship between more kinks and being less fluid (or fluidity in general)?
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    (Original post by MedicalMayhem)
    So kinks in the fatty acid tails means they are less densely packed? But you didn't answer why/how the kinks affect fluidity?

    So am I right in thinking, more cholesterol = more kinks = less fluid?

    I don't understand the relationship between more kinks and being less fluid (or fluidity in general)?
    The fluidity of the cell membrane is like oil, the cholesterol which can fit inbetween the tails can be seen as "immobilisers" if you wanna stop summat moving as much u can put wedges in stopping the tails from moving as much and as a result stopping the membrane moving as much.

    Gunna have to invisage this but if there is a wall with tiny holes in and bigger gaps keep appearing in it, it means that at somepoint in that wall a small gap somwhere decreases in size, the cholesterol will act as a wedge stopping these gaps from decreasing. So there will be less random sized holes in the wall
 
 
 
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