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35 Cards in this Set
- Front
- Back
membrane permeability
permeable to... |
permeable to: small, nonpolar, uncharged molecules, water
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plasma membrane
impermeable to... |
ions and charged or polar molecules
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concentration gradient
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the difference in the concentration, [x] of a chemical b/w one side of the plasma membrane &the other
O2 and Na ions, greater [] outside the cell CO2 and K ions, greater [] inside cell |
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electrical gradient
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inner surface of the membrane= more negatively charged
outer surface= more positively charged AKA membrane potential |
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electrochemical gradient
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concentration & electrical gradients together
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diffusion
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random mixing of particles in a solution as a result of the kinetic energy of those particles
both the solvent & solute can diffuse movement from area of [high] to [low] |
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rate of diffusion depends on (5 things)
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1) temperature (+,+)
2) size of particles (<,+) 3) steepness of gradient (+,+) 4) surface area (>,-) 5) diffusion distance/ thickness of membrane (the thicker the slower) |
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osmosis
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net movement of a SOLVENT through a selectively permeable membrane
i.e. mvmnt of water (the solvent) from an area of [higher] to [lower] across the membrane water moves via diffusion through lipid bilayer or aquaporins |
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hydrostatic pressure
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pressure that the water column exerts (prevents water from diffusing through the membrane)
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osmotic pressure
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pressure a solution exerts when its particles are not permeable to the membrane; proportional to [solute] particles that cannot cross the membrane
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molarity
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concentration of a particular solute in a solution
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osmolarity
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ratio of solute to solvent
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hypertonic
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tonicity of the solution is higher than tonicity of the cell
higher [impermeable solute] outside of cell than inside |
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hypotonic
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tonicity of the solution is lower than the tonicity of the cell
higher [impermeable solute] inside the cell than outside |
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hemolysis
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when the cell swells due to being in a hypotonic solution, RBC undergoes this
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crenation
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when a RBC shrinks, looses too much water, due to being in a hypertonic solution
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types of passive transport
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1-diffusion
2-diffusion through ion channels 3-facilitated diffusion |
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1) diffusion through the lipid bilayer
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nonpolar, hydrophobic molecules (respiratory gases, some lipids)
important for gas exchange, nutrient absorption, waste excretion |
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types of ion channels
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1-leakage channels
2-voltage-gated channels 3-ligand-gated channels |
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leakage channels
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gates alternate from open to closed
type of ion channel |
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voltage-gated channels
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type of ion channel
open in response to a change in membrane potential (aka electrical gradient) |
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ligand-gated channels
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type of ion channel
open & close in response to a chemical stimuli like hormones, neurotransmitters or other ions |
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diffusion through ion channels
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most membrane channels are ion channels
allow passage of small, inorganic, hydrophilic ions these channels are selective & specific |
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facilitated diffusion
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1) solute binds to a specific transporter protein
2) transporter undergoes conformational change 3) solute moves across membrane and is released on other side (down its conc. gradient) |
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solutes that move via facilitated diffusion
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glucose, urea, fructose, galactose, some vitamins
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primary active transport
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-most prevalent - Na/K pump
-requires 40% of cellular ATP ---energy from ATP changes shape of a transporter protein -maintains low [Na+] and high [K+] in the cytosol -operates continually -maintains & regulates cell volume |
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Na/K pump how much in how much out?
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3 Na+ ions are exported out
2 K+ ions are imported into cell ((all against gradient)) |
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secondary active transport
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*creates ion gradients
Energy stored in Na+ or H+ ion concentration gradient used to drive other substances AGAINST their own concentration gradients (usually Na influx) there are 2 types: symporters and antiporters |
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symporters
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aka cotransporters
moves substrates in the SAME direction (Na/glucose, Na/K/Cl, Na/Cl) |
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antiporters
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aka exchangers
moves substrates in OPPOSITE directions (Na/Ca exchanger, Na/H exchanger) |
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vesicle
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small membranous sac formed by budding off from an existing membrane
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endocytosis
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bringing something into the cell
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exocytosis
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release something from cell
-vesicles form inside cell, fuse to cell membrane -release their contents (digestive enzymes, hormones, neurotransmitters or waste products) |
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phagocytosis
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cell eating by macrophages and WBCs
-type of endocytosis |
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pinocytosis
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cell drinking
-type of endocytosis |