bio Chapter_7 - Chapter 7 Cellular Membranes Basics...

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Chapter 7 : Cellular Membranes Basics Composed primarily of phospholipids and proteins Bilayer with a hydrophobic core The ER is responsible for the synthesis of the cellular membrane Membrane is a fluid mosaic Mosaic of phospholipids and proteins Proteins are also amphipathic (have hydrophillic and hydrophobic regions) Proteins are embedded within the phospholipids Fluid because phospholipids and proteins are constantly moving Held together by hydrophobic interactions (much weaker than covalent bonds) Cholesterol is also embedded in the membrane Makes membrane less fluid at high temps Keeps it more fluid at lower temps (inhibits solidification) Typically about the consistency of salad oil Proteins perform most of the functions of the membrane Permeability of the Membrane The plasma membrane exhibits selective permeability , allowing some substances to cross it more easily than others Permeability of a molecule through the membrane depends on the interaction of that molecule with the hydrophobic core of the membrane.
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Hydrophobic molecules, like hydrocarbons, CO 2 , and O 2 , can dissolve in the lipid bilayer and cross easily Ions (charged molecules – typically surrounded by a hydration shell) and polar molecules pass through with difficulty This includes small molecules, like water, and larger critical molecules, like glucose and other sugars Proteins can assist and regulate the transport of ions and polar molecules Due to the cellular membrane’s selective permeability, molecules must move across the
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bio Chapter_7 - Chapter 7 Cellular Membranes Basics...

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