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Plasma cell membrane function?
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Characteristics of plasma cell membranes
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cell membrane/nerves

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
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
Biological membranes an assembly of lipid and proteins held together by noncovalent interactions
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)
Protein molecules *dissolved in lipid bilayer *mediate the functions of the membrane
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
Transport of Ions & Molecules (where) extracellular-outside fluids(interstitial & blood) intracellular-inside fluids(inside cytoplasm)
Extracellular fluids 1.*interstitial fluid-spaces between the cells/ 2. Blood plasma fluids-passes out of capillary walls and contains nutrients & gases; removes waste
Intracellular fluids *enclosed by semipermeable membranes that maintain unequal concentrations of ions on either side of membrane
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
Structure pieces of cell membrane: * Lipid bi-layer * Phospholipid *Amphipathic molecules
Lipid Bilayer *has a hydrophlic(H2Olove) and a hydrophobic(H2Ohate)end; both negative and positive
Phospholipid is the main component of the membrane and has bipolar heads, and hydrophobic lipid tails; contains double bonds
Amphipathic molecules in aqueous environments to protect hydrophobic tails; form micells or bilayers
Red Blood Cells often used for membrane study because they have no organelles or nuclear membranes
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
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)
Glycolipids (sugar lipids) lipid molecules with oligosaccharide groups exposed at the out cell surface;THOUGHT TO BE USED FOR INTERCELLULAR COMMUNICATION***
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
Lateral diffusion rates of membrane proteins can be quantified and show rotational an dlateral diffusion but not flip flop ex. centrifuge .....
Tight junctions specialized cell junctions that build wall around proteins ; restrict lateral mobility of the membrane proteins
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
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***
**The more potential a cell has, the more need for oxygen and nutrients it has; Brain cells require more energy .....
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***
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
What is the goal of the Nernst Equation? gives the diffusion potential as it is related to concentration differences; "Nernst Potential"
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
**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 .....
Characteristics of membranes: *water can pass freely *charged molecules cannot pass freely *membrane transport proteins move a specific molecules across the membrane *passive transports
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)
Passive transport of solutes: they move across the membrane according to their concentration gradient(Na/K pump always 2Kin for every 3Naout)
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
The membrane potential is maintained by: a Na+/K+ pump which actively pumps Na(dogs) out and K(cats) into cell(house)
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
ATP hydrolysis provides the energy for Na-K pump; Na+ - K+ ATPase controls the cell volume by controlling the solute concentration inside the cell
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
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
**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
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
Gated transmembrane channels(ways to get in cell) transport proteins that only open transiently
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
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"
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
ENDOCYTOSIS INGESTION; 2 WAYS 1.pinocytosis-cell drinking;fluids or small solute 2.phagocytosis-cell eating-ingestion of large particles
Created by: tbradford
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