Chapter 7 - Chapter Seven: Membrane Structure and Function...

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Definitions 1) Selective permeability: is what allows some substances to cross the cell membrane more easily than others. 2) Viscous: closer to solid state than to liquid. Notes - The cell membrane is mainly made up of lipids, proteins and carbohydrates. - Phospholipids of the cell membrane and amphipathic meaning that they have both a hydrophilic and a hydrophobic region. - Fluid mosaic model: It is the model of the cell membrane that suggests that the membrane is a fluid structure with a mosaic of various proteins embedded in or attached to a double layer (bilayer) of phospholipids. Such a double layer of molecules could exist as a stable boundary between two aqueous compartments because the molecular arrangement shelters the hydrophobic tails of the phospholipids from water while exposing the hydrophilic heads to water. Most of the lipids and some of the proteins can shift about laterally but it is quite rare for a molecule to flip-flop transversely across the membrane. Cholesterol makes the membrane less fluid: o By restraining phospholipid movement. o By lowering the temperature required for the membrane to solidify. Proteins found in the membrane: o Integral proteins: They penetrate the hydrophobic core of the lipid bilayer. Transmembrane proteins are the ones that span the membrane. Integrins are a type of integral proteins that combine to give animal cells a stronger framework. o Peripheral proteins: They are appendages loosely bound to the surface of the membrane. Molecules that start on the inside face of the ER end up on the outside face of the plasma
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Chapter 7 - Chapter Seven: Membrane Structure and Function...

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