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University of Louisville BIO 240- Rabin Exam 2 Study Guide Phospholipids  Make up the phospholipid bilayer  Amphipathic molecule= partially hydrophilic and hydrophobic  2 parts= hydrophi... lic head and hydrophobic tail  Hydrophobic tail= fatty acids linked by C-H bonds, non-polar (because of C-H bonds) making it hydrophobic  Hydrophilic head= made of choline, PHOSPHATE GROUP, and glycerol; charged and/or polar making it hydrophilic  Move around (twirl), but cannot flip sides because hydrophilic head cannot cross hydrophobic tail region  Can be saturated/unsaturated which affects fluidity (see cholesterol) Fluid Mosaic Model Components of membranes  Extracellular= Hydrophilic – Intermembrane= hydrophobic – Intermembrane – hydrophilic  Phospholipid bilayer  Cholesterol (in phospholipid bilayer)  Integral proteins (stretch across membrane)  Peripheral proteins (intermembrane side)  Cytoskeleton (intermembrane side)  Glycoproteins (extracellular side, used for cell-cell communication)  Glycolipids (extracellular side, attached to glycoprotein ^^, used for cell-cell communication) Saturated vs. unsaturated membrane  Saturated= viscous= fatty acids in tails have NO double bonds, no kinks in phospholipid tails, straight tails= ability to pack closely together= minimal fluidity= less movement in membrane  Unsaturated= fluid= fatty acids have 1+ double bonds= kinks in phospholipid tails, bent tails= unable to pack closely together= more fluidity= more movement in membrane  Most membranes have medium fluidity Cholesterol  In membrane between phospholipids, regulates phospholipid movement  Warm temperatures= restrains movement= more tight packing  Cool temperatures= promotes movement= less tight packing  Temperature changes= different cholesterol effects because it prevents phospholipids from moving out of the membrane when hot, and from not moving and freezing when cold Integral membrane proteins  Stretch across membrane  Amphipathic  Transport proteins= carrier and channel  Used in facilitated diffusion and active transport  Carrier proteins= change in shape, transport smaller polar organic molecules, ACTIVE diffusion ONLY, hydrophilic route  Channel proteins= do NOT change shape, continuous path across membrane, PASSIVE transport, hydrophilic route for smaller polar molecules and ions, Peripheral membrane proteins  Does not extend to both sides of the membrane  Intermembrane side ONLY  Responsible for cell signaling (molecules can bind to this protein on the outside to change cytoplasm) 6 Jobs of membrane proteins  A- Transport  B- Enzymatic activity  C- Attach to cytoskeleton and extracellular membrane  D- Cell to cell recognition (glycolipids and glycoproteins)  E- Intercellular joining (ex. gap and tight junctions)  F- Signal transduction Sidedness of membranes  See fluid mosaic model and components of membranes Types of molecules that can cross the membrane  Small non-polar molecules (hydrocarbons, O2 and CO2)= hydrophobic, can cross easily WITHOUT TRANSPORT PROTEIN  Polar molecules (H20, sugars)= hydrophilic= can’t pass easily through hydrophobic part, NEEDS TRANSPORT PROTEIN  Ions (polar) (Na+, K+, Ca 2+, Cl-)= hydrophilic= can’t pass easily through hydrophobic part, NEEDS TRANSPORT PROTEIN Membrane transport- Active  Moves substances AGAINST concentration gradient  Low  high  Requires energy  ALWAYS use carrier transport proteins  Sodium potassium pump= COtransport= Na+ low, K+ high inside cell= Na+ high, K+ low outside of cell= moves Na+ to outside of cell= moves K+ to inside of cell  Steps of SPP= 1. Na+ binds to pump in cytoplasm, affinity of Na+ is high; 2. Na+ binding stimulates phosphorylation of ATP (electron transport chain creates gradients); 3. Phosphorylation (creates gradients), change in protein shape, low affinity for Na+, releases Na+ out of the cell; 4. New shape has high affinity of K+, binds to extracellular side, triggers release of phosphate group; 5. Loss of phosphate group, original shape (cycle), low affinity of K+; 6. K+ released to intermembrane space, affinity Na+ is high, cycle repeats Membrane transport- Passive  Moves substances WITH concentration gradient  High  low  NO ENERGY REQUIRED  Diffusion, facilitated diffusion and osmosis  Diffusion= non-polar hydrophobic particles= WITHOUT TRANSPORT PROTEINS= diffuse until equilibrium (not in living cells though)  Facilitated diffusion= polar hydrophilic molecules= NEEDS TRANSPORT PROTEINS!!= water= aquaporin transport proteins, ions= channel transport proteins  Osmosis= diffusion of water Membrane transport- Bulk (Endocytosis vs Exocytosis)  Big molecules  Requires energy  Particles packaged in vesicles  NO PROTEINS  Endocytosis= inward folding of membrane, vesicle forms around molecule, decreases membrane surface area, vesicle binds with intercellular side of membrane, contents spill INTO cell  Exocytosis= vesicle forms in cytoplasm, binds with extracellular side of membrane, contents spill OUTSIDE of cell [Show More]

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