Week of August 30- September 5 Notes
Week of August 30- September 5 Notes EXSC 223 001
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This 10 page Class Notes was uploaded by Holly Vaughn on Monday September 7, 2015. The Class Notes belongs to EXSC 223 001 at University of South Carolina taught by Thompson in Summer 2015. Since its upload, it has received 153 views. For similar materials see Anatomy and Physiology 1 in Physical Education at University of South Carolina.
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Date Created: 09/07/15
33 Passive membrane transport is diffusion of molecules down their concentration gradient 0 Two main types of passive transport 0 Diffusion tendency for molecules to move form area of higher concentration to an area of lower concentration Passive process Driven by kinetic energy Affected by 1 size 2 gradient 3 temperature 0 Filtration Mainly across capillary walls Diffusion moves along the CONCENTRATION GRADIENT How 0 Constant random fast movement of molecules makes a collision Driving force kinetic energy 0 They collide and ricochet off of one another 0 They go in opposite directions 0 ln closed container diffusion makes a uniform mixture reaches equilibrium where molecules move equally in all directions 0 Overall effect to scatter or disperse the particles throughout the environment 0 EX drop a bath bomb in the tub watch it change the color of the whole solution 0 What affects the speed of diffusion 0 Size the smaller the faster 0 Temperature the warmer the faster 0 Examples of diffusion in physiology 0 Movement of ions across cell membranes 0 Movement of neurotransmitters across two nerve cells 0 The plasma membrane is a Selectively or Differentially Permeable Barrier o It allows some substances to pass while excluding others 0 Enter nutrients keeps valuable cells proteins in 0 Exit wastes undesirable substances 0 Barrier to free diffusion 0 Characteristic of healthy intact cell Homeostatic imbalance in selective barrier 0 Cell is severely damaged Membrane is permeable to everything and substances flow into and out freely When will a molecule diffuse through the membrane 0 Simple diffusion unassisted diffusion of a lipid soluble or small particles driven by kinetic energy What goes through Nonpolar fat soluble lipidsoluble substances amp small molecules diffuse through lipid bilayer 0 Oxygen carbon dioxide fatsoluble vitamins Examples Oxygen higher in blood than in tissues so it diffuses from blood into the cells Carbon dioxide higher in tissue cells so it diffuses from tissue cells into the blood 0 Facilitated diffusion assisted diffusion by carrierchannel driven by kinetic energy Glucose sugars amino acids ions diffuse but NOT through the lipid bilayer either through 1 binding to protein carrier in the membrane to be carried across OR 2 moving through water lled protein channels Carrier Mediated Facilitated Diffusion What goes through 0 Lipid soluble glucose amino acids large molecules Carriers transport the proteins that are too large to pass through the membrane channels lipid insoluble solutes Carrier protein changes shape embedded in membrane to move the binding site solute from one side of the membrane to the other Channel mediated facilitated diffusion Channels are trans membrane between the membrane proteins They transport ions or water through the AQUEOUS channel from one side of the membrane to the other They are SELECTIVE due to pore size and charges of the amino acids lining the channel Leakage channels always open allow ions or water to move according to concentration gradient rules Gated channels controlled by chemical or electrical signals opened or closed 0 Osmosis diffusion of water across the membrane from low to high solute concentration makes sense if there is more solute there should be more water when separated by a semipermeable membrane Diffusion of WATER throuoh a selectivelv permeable membrane lipid bilayer OR through a channel protein called the AQUAPORIN They are abundant in red blood cells and kidney cells where water needs to be balanced Moves from a solution of lesser osmolarity to a solution of greater osmolarity Osmolarity BASED SOLELY ON total concentration of all solute particles in a solution Equilibrium is reached when the solutewater concentration is the same on both sides When looking at gure 38 you see that the U shaped container is lled with water evenly on both sides Same osmolarity because the membrane is FREE permeable to all molecules in system on the other hand when you have a selectively permeable membrane the solution will have the same osmolarity but one side will have a greater volume only water is free to move through it Hydrostatic pressure pressure of uid in a system against the membrane Osmotic pressure tendency to move water into cell by osmosis Tonicity ability of a solution to change the shape or tone of cells by altering the cells39 internal water volume How the solution affects cell volume Solute concentration Solute permeability of plasma membrane Types 3 lsotonic cell retains normal shape 0 Same solutewater concentration inside as outside 0 Water moves in and out 0 Same concentration of nonpenetrating solutes as in the cell Hypertonic cell loses water shrivels shrinks Higher concentration of nonpenetrating solutes than inside the cell 0 Water moves out Hypotonic solution cell gains water bloated amp bursts Water moves in lyse Contains lower concentration of nonpenetrating solutes than inside 34 Active membrane transport directly or indirectly uses ATP 0 Active process occurs when the cell uses energy to move solutes across the membrane metabolic energy required from cell 0 Depends on ATP 0 Happens when they cannot passively go through membrane 1 Too large to pass through the channels 2 Incapable of dissolving in the lipid bilayer 3 Moving against its concentration gradient 0 Active transoort requires carrier proteins that combine speci cally and reversibly with the transported substances Solute pumps quotactive transportersquot moving solutes ions uphi again5ta concentration gradient 0 Sodium Potassium Pump Na and K Primarv Active TranSport The Sodium Potassium Pump 0 Integral protein 0 Contains sites for binding of Na and K 0 How does it regulate shape Phosphorylation ATPp ADP 1 3 Na bind to the pump from inside the cell39s cytoplasm 2 Na binding promotes hydrolysis of ATP Energy is released and used to phosphorylate the pump 3 Phosphorylation causes the pump to change shape allowing the Na to be released outside of the cell 4 Two K from the extracellular uid bind to the pump 5 K binding releases the phosphate from inside the pump see step 2 Pump becomes dephosphorylated and resumes original position inside cell 6 Pump protein binds ATP to the NaK pump this causes the pump to release the K inside the cell 7 Pump is ready to bind with Na again and the cycle repeats Secondary Active Transport 0 Energy source uses oradient we generate from the Sodium Potassium Pump 0 How does Sodium get back into the cell amp what comes with it 1 Na enters the cell with the help of a carrier protein In this process glucose is also quotdragged alongquot or quotcotransportedquot by the same carrier ag its concentratin gradient symport system same direction a If it was moving in opposite directions is would be an antiport system 2 The shape changes 3 The Na and glucose are released into the cell Vesicular Transoort transport of large particles and macromolecules into or out of a cell or between its compartments in membrane bound sacs called vesicles 0 What is it amp sometimes GTP throughout whole process 1 Moves substances into the cell endocytosis and out of the cell exocytosis as well as for combination processes transcytosis 0 moving substances into the cell and then out 0 Vesicular traf cking moving substances from one area membranous organ in the cell to another 0 Types of Vesicular Transport 1 Endocytosis movement of bulk solids macromolecules uids and sometimes pathogens hijacking not by request into the cell Coated pit enfolding of plasma membrane ingests a substance listed above It encloses the substance Pit coat type of endocytosis that aids in formation of vesicles Vesicle detaches Uncoated vesicle fuses with a quotsorting vesiclequot Endosome 0 A Fused Vesicle either fuses with lysosome to digest contents OR 0 B Delivers contents to plasma membrane on opposite side of cell TRANSCYTOSIS 3 types of Endocytosis 0 Alike use proteincoated vesicles 0 Different type or amount of material taken up and mean of uptake quotcell eatingquot o 0 Cell engulfs large solid particles clump of bacteria deb s 0 Has receptors which are capable of binding to microorganisms or solid particles 0 Phagosome combines with a lysosome 0 Undigested contents A remain in vesicle residual body or B are ejected by exocytosis If ejected dead cell remains can trigger in ammation 0 Amoeboid flow of cytoplasm into temporary extensions allowing movement quotchanging shapequot 0 quotcell drinkingquot Ex cells absorbing nutrients cells lining intestines 0 Fuses with an endosome 0 Cell loses part of plasma membrane and are removed when the membranous sacs are internalized Loss of membrane from cell returns back to plasma membrane by exocytosis Surface area stays constant of membrane 0 IAffords a 39 main mechanism for the is and transcytosis of most macromolecules by body cells Caveolae different type of coat protein tubular ask shaped inpocketings of the plasma membrane involved in unique RME Smaller amp thinner than Clathrin coated vesicles 2 process of vesicular transport where substances are ejected from the cell39s interior to the exterior CALCIUM TRIGGERS EXOCYTOSIS Stimulated by a cellsurface signal such as binding of a hormone to a membrane receptor or a change in membrane voltage What exits Hormone secretion Neurotransmitter release Mucus secretion Ejection of waste 0000 o Substances to be removed EXO from the cell is rst enclosed in a protein coated membranous sac Secretory Vesicle Transport and Digestion Cells Segregate internal and external environments avia the plasma membrane regulate Permit selected substances across the plasma membrane and through the cytosol via different passive or active mechanisms 0 Diffusion and Osmosis 0 Active Transport primarysecondary 0 Passive Transport Identi cation of alien invaders 1 Cellcell recognition 2 Glycoproteins serve as identi cation tags that are speci cally recognized by other cells Cells have skeletons too 0 Provides supporting cellular structure 0 Provides machinery to generate cell movement 0 Cytoskeletonsr Help maintain integrity of the cell Aids in movement Organelles within the cell movement 0 Micro lament attached to the cytoplasmic side of the cell membrane giving strength to the cell surface 0 Intermediate lament high tensile strength and resists pulling forces Toughest most brous element in the cell Pulling forces stands high tensile stretching force Desmosomes is associated with it Many of these go from membrane to microtubules somewhere in the cell Distributes stress across a large area 0 Microtubules cell shape and distribution of cell organelles Made of Actin class of proteins F Actin forms twisting laments Stabilizes plasma membrane by holding proteins in place Relates to movement of cells Binds to integral and peripheral proteins Ex how mucus gets moved into the back of your throat 0 Motor proteins quotMyosinquot protein that can move Walks along microtubule by ATP to help transport vesicles EX Moves like zombie legs amp powered by ATP carrying vesicle overhead 0 Motor molecules attached to one element of the cytoskeleton can cause it to slide over another element as in muscle contraction and cilia sperm movement Ex Zombie legs walking on pipe microtubule carrying another pipe microtubule over its head and powered by ATP 0 Centrioles small barrel shaped organelles located in the centrosome near the nucleus Pinwheel array of 9 triplet of microtubules Key role in Mitosis organize mitotic Cells form tissue and organs by holding hands Specialized membrane proteins help cells hold on to one another 35 Selective diffusion establishes the membrane potential Membrane potential voltage across a membrane 0 Voltage electrical potential energy resulting from the separation of oppositely charged particles 0 lons oppositely charged particles in cells 0 Plasma membrane the barrier keeping the particles apart Resting membrane potential voltage cells exhibit in the resting stage 0 Concentration and electrical gradients determine the ease of and ion39s diffusion 0 Range 50 to 100 mivots O Minus sign inside of cell is negatively charged Voltage exists only at membrane When adding all the charges of the cytoplasm amp extracellular uid are actually neutral How is it generated K is the key player Diffusion causes ionic imbalances that polarize the membrane K diffuses down their concentration gradient out of the cell through LEAKAGE CHANNELS Loss of K in the cell results in a negative charge one the inner plasma membrane face where the membrane and cytoplasm meets K also move into the cell Attracted to the negative charge on inner plasma membrane face 0 A negative membrane potential 90 mV is made when the K movement outside the cell is equal to the K movement inside the cell 0 At this point concentration gradient promoting K exit exactly opposes the electrical gradient for K entry 0 Sometimes Na can come into the cell bc it is attracted to the negative charges inside lowering the membrane potential to 70 mV Active transport processes maintains that membrane potential By concentration gradients of ions and the differential permeability of the plasma membrane to ions usually potassium ions 0 Active Transport maintains electrochemical gradient 0 O 0 Cell exhibits a steady state Rate of active transport OUT of the cell is equal to and depends on the rate of Na diffusion into the cell Membrane is 25x more permeable to K than Na ATP dependent pump NaK Pump maintains both the membrane potential and the osmotic balance Pumps 3 Na out of the cell amp 2 K back in IF Na was not pumped out the cells would burst Hyper Diffusion is affected by Concentration gradients and by electrical charge on inner and outer faces of membrane called the Electrochemical gradient Transient opening of gated Na and K channels in the plasma membrane quotupsetsquot the resting membrane potential