cell membrane physiology
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| Plasma cell membrane function? | encloses every cell, defines the cells extent & maintains difference between its contents &it's environment
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| Characteristics of plasma cell membranes | * has a selective filter that *maintains unequal concentration of ions on either side *allows nutrients to enter & waste products to leave cell
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| Biological membranes | an assembly of lipid and proteins held together by noncovalent interactions
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| Lipid layer | *the basic structure of cell membrane *serves as impermeable barrier to flow of most water soluble molecules(it does not let water soluble elements in)
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| Protein molecules | *dissolved in lipid bilayer *mediate the functions of the membrane
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| Protein molecules functions | 1. transport molecules in & out 2. form enzymes to catalyze membrane rx 3.serve as structural links between cells cytoskeleton & extracellular 4. are receptors that recieve & tranduce chemical signals from cells envnt
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| Transport of Ions & Molecules (where) | extracellular-outside fluids(interstitial & blood) intracellular-inside fluids(inside cytoplasm)
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| Extracellular fluids | 1.*interstitial fluid-spaces between the cells/ 2. Blood plasma fluids-passes out of capillary walls and contains nutrients & gases; removes waste
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| Intracellular fluids | *enclosed by semipermeable membranes that maintain unequal concentrations of ions on either side of membrane
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| Ways proteins in cell membranes mediate cell function by: | 1. transport molecules in & out 2. composes molecules that catalize rx 3. form link between cells cytoskeleton on extracellular matrix 4. forms receptors for recieving & tranducing chemical signals
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| Structure pieces of cell membrane: | * Lipid bi-layer * Phospholipid *Amphipathic molecules
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| Lipid Bilayer | *has a hydrophlic(H2Olove) and a hydrophobic(H2Ohate)end; both negative and positive
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| Phospholipid | is the main component of the membrane and has bipolar heads, and hydrophobic lipid tails; contains double bonds
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| Amphipathic molecules | in aqueous environments to protect hydrophobic tails; form micells or bilayers
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| Red Blood Cells | often used for membrane study because they have no organelles or nuclear membranes
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| Red Blood cells contain: | 1. spectin-serve as attchmnt for cytoskeleton 2. glycophorins-glycoproteins and sugar residues 3.Band III trans membrane proteins-aid in O2 and CO2 exchange
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| Lipid Bilayers composition | *2 dimentional fluid that determines its fluidity; increased double bonds increase fluidity; (the more double bonds, the more fluid the membrane which is good)
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| Glycolipids (sugar lipids) | lipid molecules with oligosaccharide groups exposed at the out cell surface;THOUGHT TO BE USED FOR INTERCELLULAR COMMUNICATION***
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| 3 types of membrane proteins:(make up 50%of membrane by weight) | 1. peripheral-are easily removed; can seperate
2. integral-difficult to remove; trapped
3. transmembrane-extend accross the bilayer and are exposed to water environment on both sides
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| Lateral diffusion rates of membrane proteins can be quantified and show rotational an dlateral diffusion but not flip flop ex. centrifuge | .....
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| Tight junctions | specialized cell junctions that build wall around proteins ; restrict lateral mobility of the membrane proteins
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| Membrane Transport of small molecules | selective permeability in membrane causes potential energy in the form of ion gradients; these are used to make ATP and drive transport processes and covey electrical signals
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| Membrane Potentials(action potentials-to do work) | *excesses of - ions(anions) accumulate immediately inside cell membrane
*equal number of + ions(cations) are outside the membrane **this difference in charge is called the potential***
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| **The more potential a cell has, the more need for oxygen and nutrients it has; Brain cells require more energy | .....
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| Potential difference is caused by:(two movements) | 1. Diffusion- movement due to difference in ion concentrations
2.Active transport-movement of ions with enregy being expended also cause on imbalance of charges****ATP***
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| Active Transport creates: | *large K+ concentration inside cell; small concentration outside(cats inside house)
*high concentration of Na+ outside cell; low concentration inside cell(dogs outside house)
*Na K+ pump exchanges to keep energy
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| What is the goal of the Nernst Equation? | gives the diffusion potential as it is related to concentration differences; "Nernst Potential"
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| The Goldman Equation shows that: | the potential is determined by;
1.the polarity of the electrical charge of K+, Na+, and Cl-
2. the permeability of the membrane to each ion
3. the concentration of each ion on the in and out of membrane
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| **some cells are more permeable; permeabilities of Na and K channels undergo very rapid changes during conduction of the Nerve Impulse *CL- permeability doesnt chagne much | .....
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| Characteristics of membranes: | *water can pass freely
*charged molecules cannot pass freely
*membrane transport proteins move a specific molecules across the membrane
*passive transports
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| Membrane transport proteins; 2 kinds? | 1. Uniports-transports one solute from one side to another2. co-transport-transfer of one solute depends on the simultaneous transfer of a second solute (symport-move same direction;antiport-opposite directions)
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| Passive transport of solutes: | they move across the membrane according to their concentration gradient(Na/K pump always 2Kin for every 3Naout)
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| Transport proteins mediate passive transport by: | channel proteins-aqueous channges permit solutes to cross the bilayer by diffusion carrier proteins-(transporters)bind the molecule and transfer it across the membrane(facilitated diffusion) active transport-pumps actively drive the mvemnt of solutes uphl
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| The membrane potential is maintained by: | a Na+/K+ pump which actively pumps Na(dogs) out and K(cats) into cell(house)
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| K+ leak channel allows what? (all proteins) | K+ to leak out of the cell resulting in a negative charge within the cell and an electrical gradient or membrane potential
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| ATP hydrolysis | provides the energy for Na-K pump; Na+ - K+ ATPase controls the cell volume by controlling the solute concentration inside the cell
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| Calcium Pumps(memebrane bond ATPases); calcium is a signalling agent | help maintain very low concentrations of Ca+ inside the cell while outside concentration is high;the flow of Ca down the gradient into cell is means of transmitting signals across membrane
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| ATP Synthetases | are transport ATPases working in reverse;instead of hydrolysis driving ion transport, H+ gradients across the membranes drive the synthesis of ATP from ADP + Pi(inorganic phosphate):eat---make ATP---cell functions
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| **Active transport can be driven by the energy stored in ion gradients rather than directly by ATP hydrolysis | ex:in mammals, active transport of sugars is powered by Na gradient-a symport system: dogs+sugar to get into cell; high energy concentration into a low energy concentration in the cell
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| Group translocation | an active transport method where a molecule is modified in a way that it can't escape through the same channel it entered through: these "trapped" molecules maybe ionized
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| Gated transmembrane channels(ways to get in cell) | transport proteins that only open transiently
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| 3 Types of gated transmembrane channels | 1.Ligand gated-a ligand(insulin or ACH)fits into protein and allows something to move into cell protein molecule by CHANGING SHAPE 2.voltage gated channels-neuro imput;change the charge to let it in 3.ionic channels-like calcium helping open to let in
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| Inophores | *small hydrophobic molecules that dissolve in lipid bilayers & increase the ion permeability(ex; alchohol changing its shape & cell membrane permeability; it fluidizes the membrane; muscle/nerve cells to not act right:"drunk"
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| 2 types of membrane transport of Macromolecules & particles: | 1.exocytosis-fusion of intracell vesicles w/subsequent release to the exterior 2.endocytosis-substance to be ingested is enclosed by small portion of plams membrane and BECOMES AN INTRACELLULAR VESICLE
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| ENDOCYTOSIS INGESTION; 2 WAYS | 1.pinocytosis-cell drinking;fluids or small solute 2.phagocytosis-cell eating-ingestion of large particles
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