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Phospholipid Bilayer question

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    Membranes are made up of a phospholipid bilayer. What is the use/function of:
    • cholesterol
    • glycoprotein
    • integral proteins embedded in the phospholipid bilayer


    I'm revising for an exam in 2 days so please help
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    Cholesterol molecule straightens out hydrocarbon chains. Glycoprotein- for communication and transport (i think)

    and proteins for transport- eg carrier proteins
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    Glycoproteins branch off into the surrounding fluids and stabilise the cell.
    They are also used for intracellular messaging (Antigens specifically).

    The embedded proteins could be carrier proteins / protein channels which are used in Active Transport in and out of the cell i.e. Na+ or they could be enzymes such as ATPase.

    Cholesterol maintains mechanical stability.
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    Cholesterol; to stabilise the bilayer as it would be too fluid without it.
    Glycoproteins; to act as receptors(I think)
    Integral Proteins: ion pores(to transport ions) or transport proteins(to carry glucose and amino acids)
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    Lol this thread proves how long ago it was since i did biology a-level!
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    (Original post by Hobnobs Galore)
    Lol this thread proves how long ago it was since i did biology a-level!

    Lol. count yourself lucky; it's a nightmare.
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    cholesterol stablises the membrane.
    glycoproteins are used as receptors i think.
    other proteins are used as carriers or to create channels to help transport ions/molecules across the membrane.

    hope it helps a bit!
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    (Original post by G O D I V A)
    Membranes are made up of a phospholipid bilayer. What is the use/function of:
    • cholesterol
    • glycoprotein
    • integral proteins embedded in the phospholipid bilayer


    I'm revising for an exam in 2 days so please help
    I'll help myself helping you by doing this Interview tomorrow in Cambridge - might come up:

    Cholesterol does maintain membrane fluidity - it increases fluidity at lower temperature, and vice versa at higher temperatures. The mechanism is that it acts as a wedge to seperate the phospholipid a little, thereby reducing Van Der Waals bonding and also increasing permeability to molecules.

    Glycoprotein acts as cell recognition proteins - "self and non self" really.

    Integral proteins -
    Carrier proteins - actively transport molecules across the membrane against a concentration gradient (e.g. Na - K pump).

    Protein Channels - provides a hydrophilic channel through which water solutes can diffuse through, though the protein is specific [question to others: am I right in saying this is facilitated diffusion?]

    Protein Receptors - a ligand attaches to the substrate of the protein on one end, and the other end sends a cascade signal inside the cell, expressing or inhibiting a certain gene from T&T a protein.

    Cell Adhesion - certainly some attach to the cytoskeleton inside the cell, and attach to other cell membranes.

    lol, wall of text there. Hope this helps!

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Updated: December 7, 2008
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