Test guide 2 - Test#2 Study Guide Plasma membranes made of lipids proteins and carbohydrates mostly lipids like phospholipids Selective permeability

Test guide 2 - Test#2 Study Guide Plasma membranes made of...

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Test #2 Study Guide Plasma membranes : made of lipids, proteins, and carbohydrates, mostly lipids like phospholipids Selective permeability: plasma membrane allows some substances to cross it more easily than others Amphipathic: mcl that has both a hydrophilic and hydrophobic region. Ex: phospholipids (center is hydrophobic and head is hydrophilic) Fluid mosaic model: the membrane is a fluid structure with a mosaic of various proteins embedded in or attached to a double layer (bilayer) of phospholipids Movement of phospholipids: lipids move laterally in the membrane (10 7 time per second) and flip-flop rarely, b/c the hydrophilic part must cross the hydrophobic part Fluidity o Temp controls fluidity in membrane, dec in temp membrane becomes more rigid o Saturated hydrocarbon tails make the membrane viscous (thick) o Unsaturated hydrocarbon tails with kinks make the membrane fluid, have holes and leaky o Want to have a moderate viscosity, so have a mixture of saturated and unsaturated tails and have a cholesterol added in the membrane too Cholesterol reduces membrane fluidity at moderate temps by reducing phospholipid movement, at low temps it hinders solidification by disrupting the packing of phospholipids Integral proteins : penetrate the hydrophobic core of the lipid bilayer. Many are transmembrane proteins which span the membrane, other integral proteins extend only partway into the hydrophobic core Peripheral proteins: are not embedded in the lipid bilayer at all, they are appendages loosely bound to the surface of the membrane, often exposed to parts of integral proteins Transmembrane proteins (Passive transport) – transport specific ions o Amphipathic – has a region that is hydrophobic and hydrophilic on the same mcl (phospholipids are amphipathic too), stuff on the extracellular side have to be hydrophilic. Internal of the protein is hydrophobic in the center of the mcl which helps it remain stable in the plasma membrane Hydrophilic mcls can’t fit through the plasma membrane b/c the inside is hydrophobic, this is where the transport proteins come in to help The internal surface of the transport protein has different R- groups which allows the hydrophilic mcls to pass through o Membrane proteins and their functions: transport, enzymatic activity, signal transduction cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and extracellular matrix (pg. 129) o Transport proteins Nonpolar mcls are hydrophobic and cross the membrane easily without the aid of membrane proteins
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Polar mcls and ions are hydrophilic and pass through the membrane slowly Hydrophilic mcls can pass through the lipid bilayer by passing though transport proteins, which some have chanzzznel proteins Channel proteins which allow certain mcls use as a tunnel through the membrane Ion channels, many of which are gated channels which open or close in response to a stimulus.
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