Term
| 2 main classes of membrane protein which mediate transfer of molecules across bilayers |
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Definition
1. Transporters- moving
2. Channels- hydrophillic pore allowing passive mem. transport |
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Term
| Cells must be electrically... |
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Definition
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Term
| Most cell constituents are what? Ex:? |
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Definition
| Negatively charged. ex: HCO3-, PO43- |
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Term
| No protein is needed for? |
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Definition
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Term
| Prot. free bilayers are impermeable to? |
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Definition
| Ions b/c charger doesn't allow them to pass through hydrophobic bilayer |
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Term
| Hydrophobic molecules freely pass thru the bilayer such as? |
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Definition
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Term
| Some small UPM and some larger UPM pass freely thru the mem. such as? |
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Definition
H20, urea, glyerol (SUPM)
glucose, sucrose (LUPM) |
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Term
| Define how transporter fxns |
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Definition
| bind specific mol. to be transported thru conformation difference when bound, then transfers across mem. |
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Term
| Define how channel prot. fxns |
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Definition
| Interacts much weaker than transporters. Forms aq. pores across bilayer |
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Term
| All channels & most transporters only allow passive transport via? |
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Definition
| Conc. gradient, which determines direction. |
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Term
| Passive transport occurs across bilayer & what through channels and passive transporters? |
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Definition
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Term
| Active Transport is done how? |
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Definition
| Through ATP Hydrolysis and Ion Gradient |
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Term
| AT is always mediated by and against what? |
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Definition
| Transporters. Against conc. or electrochem. gradient. |
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Term
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Definition
| simple diffusion, passive transport (channel-mediated & transporter mediated), AT (transporter mediated against gradient) |
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Term
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Definition
| combo of conc. gradient and mem. potential |
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Term
| Transporters undergo conformations like? |
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Definition
| Enzymes and their substrates |
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Term
| Diff. btwn transporters and enzymes? |
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Definition
| Transporters only transport, they do not modify mol. |
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Term
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Definition
| ..which carrier can flip btwn conformational states |
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Term
| Each carrier has specific affinity for mol., reflected by? |
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Definition
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Term
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Definition
| Conc. of molecule transported when transporter is at 1/2 Vmax |
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Term
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Definition
1. Coupled transport
2. ATP Driven transport
3. Light Driven transport |
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Term
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Definition
| couples uphill against conc. gradient of one molecule across mem. & downhill for the other |
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Term
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Definition
| couples uphill transport to ATP Hydrolysis |
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Term
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Definition
| mainly in bacteria & archaea, uphill transport w/ light energy |
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Term
| 3 Types of AT driven by Ion gradients |
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Definition
1. Symport
2. Antiport
3. Uniport |
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Term
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Definition
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Term
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Definition
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Term
| Transporters pump out excess H+ w/ energy stored in .. |
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Definition
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Term
| 2 mech. or pumping out excess H+ energy stored in Na+ gradient |
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Definition
1. H+ pumped out
2. HCO3- pumped in to neutralize |
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Term
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Definition
| H20 + CO2 so... NAHCO3 in and HCl out |
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Term
| Glucose transporter can be driven by? |
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Definition
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Term
| Regards of glucose transporter driven by Na+ gradient active transport: how many conformational states? |
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Definition
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Term
| Regards of glucose transporter driven by Na+ gradient active transport: Diff. btwn conform. state A and B? |
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Definition
| A prot. is open to extracell. space and B prot is open to cyto. |
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Term
| Binding of Na+ and glucose is cooperative how? |
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Definition
| Binding of either ligand leads to diff. conform. states that increase affinity for 2nd ligand. |
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Term
| Na+ conc. is higher where in regards to cell? |
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Definition
| Outside or extracell space |
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Term
| Regards of glucose transporter driven by Na+ gradient active transport: which conform. state is glucose most likely to bind to? |
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Definition
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Term
| Regards of glucose transporter driven by Na+ gradient active transport: for Na+ and glucose to enter, which conform. state is favorable? |
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Definition
| A to B happens more than B to A. Result is transport of both into cell. |
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Term
| Lactose permease occurs where in mammalian cells? More often AT driven H+ gradients occur rather than? |
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Definition
| Organelles. Na+ gradients |
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Term
| Mech. of Lactose Permease in bacteria? |
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Definition
It is an H+ Driven Transporter.
1. Transports lactose across mem. of E. coli
2. 12 mem. alpha helices |
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Term
| Bacterial Lactose Permease transporter has 2 diff. conformational states where? |
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Definition
| Extracell. side and cyto. side |
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Term
| Bacterial lactose permease transporter: Extracell. side conformational state mech. |
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Definition
-loading H+ & lactose is favored.
1. Arginine 144 forms bond with glutamic acid 126
2. Leaves glutamic acid 269 free to accept H+ |
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Term
| Bacterial lactose permease transporter: Conform. state on cyto. side mech? |
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Definition
-unloading both H+ and lactose is favored
1. arginine 144 bonds with glutamic acid 269
2. destabilizes bound H+ |
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Term
| Most cells have Na+ driven antiporters in mem. to maintain cyto.? |
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Definition
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Term
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Definition
| couples efflux of H+ with influx of Na+ |
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Term
| Na+ driven Cl-/ HCO3- exchanger |
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Definition
| combo of 2 mech. that couple influx of Na+ and HCO3- to efflux of Cl- and H+ |
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Term
| 3 Classes of ATP driven Pumps |
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Definition
1. P-type pump
2. F-typer pump (& V-type) proton pump
3. ABC transporter |
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Term
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Definition
| phosphorylates itself during pumping cycle. |
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Term
| F-type (& V-type) proton pump |
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Definition
ATP synthases.
-in inner mem. of mito.
-often work in reverse H+ gradient across mem. which drives synthesis of ATP |
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Term
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Definition
| Pump small mol. across mem. in contrast to P & F type pumps which only transport ions |
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Term
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Definition
| hydrolyze ATP --> ADP + Pi |
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Term
| Plasma mem. P-type Na+/ K+ pump establishes? |
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Definition
| Na+ gradient across plasma mem. |
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Term
| Plasma mem. P-type Na+/ K+ pump : fxn of oubain? |
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Definition
| An inhibitor that competes for same site as K+ |
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Term
| Plasma mem. P-type Na+/ K+ pump: #Na+ out and k+ in? What is this? |
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Definition
3 Na+ out for every 2 K+ pumped in
-antiporter driven by ATP |
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Term
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Definition
1. transport nutrients into cells
2. regulates cyto pH |
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Term
| Pumping cycle of Na+/K+ ATPase affects cell mem pot. how? What leads to differences in conform. states? |
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Definition
3 Na+ out and 2 K+ in leads to neg. cell inside rela. to outside.
Na+ dependent phosphorylation and K+ dependent dephosph. |
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Term
| Osmotic movement can greatly influence cell vol., what is important in RBC for controlling this? |
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Definition
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Term
| What happens to RBC put into a hypertonic solu.? |
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Definition
High conc. of ions cause H20 to move out of the cell.
*crenated |
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Term
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Definition
| Low conc. of ions causes H20 movement into the cell. Too much can cause it to lyse |
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Term
| Some transporters move mol. downhill with? |
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Definition
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Term
| Diff. btwn Gated ion channel and selectivity filter in Aq. pore? |
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Definition
Gated- open or closed and selective
Selectivity filter in Aq. pore- narrows to where only one ion can pass |
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Term
| Unlike carrier prot., channel prot form? |
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Definition
| Hydrophilic pores across mem |
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Term
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Definition
| Inorganic ions like Na+, Ca2+ or Cl- |
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Term
| Ion channels are significant for? |
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Definition
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Term
| Ions channels are faster than carrier prot., transporters can't? |
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Definition
| be couple to an energy source.. always passive transport |
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Term
| 4 Types of Gating Ion Channels and their specific stimulus |
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Definition
1. Voltage Gated (mem. pot.)
2. Extracell. Ligand Gated (Neurotransmitter)
3. Intracell. Ligand Gated (Ion or nucleotide)
4. Mechanically Gated (Mech. stress) |
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Term
| How does mem. pot. arise? |
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Definition
| When there is a diff. in electrical charge on the 2 sides of the mem. |
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Term
| Ions on one side of the mem have what on the other side? |
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Definition
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Term
| Fxn of neuron depends on? |
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Definition
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Term
| Ion channels required for fxn in? |
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Definition
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Term
| Action potentials are direct consequence of? |
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Definition
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Term
| Plasma mem. of electrically excitable cells contains? |
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Definition
| Voltage gated cation channels |
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Term
| Action potential triggered by brief pulse of current (A) which? |
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Definition
Depolarizes the mem.
-shift in mem. pot. to less neg. value inside |
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Term
| Depolarization opens up what, which allows Na+ to enter. Influx of Na+ depolarizes mem. further.. what is consequnce? |
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Definition
-opens voltage gated Na+ channels
-opens more Na+ channels= positive feedback |
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Term
| What happens when Na+ channels inactive? |
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Definition
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Term
| Voltage gated K+ channels (efflux of K+) provide? |
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Definition
| 2nd mech in addition to inactivation of Na+ channels, to bring mem back to resting potential |
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Term
| Why can action potential only travel away from the site of depol.? |
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Definition
| Because of the inactivation of Na+ channels |
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Term
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Definition
| Increases the speed and efficiency of AP propagation along axons |
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Term
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Definition
1. no myelin
2. Na+ channels are conc. so AP propagates by jumping node to node
3. Saltatory conduction (faster, conserves energy) |
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Term
| Myelin produced by glial cells.. |
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Definition
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Term
| Myelin wraps layers of plasma mem. around axons, which is insulatory. What happens in MS? |
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Definition
| Myelin degraded by autoimmune attack |
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Term
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Definition
| protein which binds at end of myelin sheath |
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Term
| Transmitter gated ion channels convert? |
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Definition
| Chem. signals into electrical signal at chem. signals |
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Term
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Definition
| special sites of contact where neuronal signals are transmitted from cell to cell |
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Term
| Neurotransmitters can be excitatory or.. |
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Definition
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Term
| Excitatory neurotransmitters |
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Definition
-open cation channels
- ex: influx of Na+ that depolarizes mem toward the threshold for firing pot. |
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Term
| Inhibitory Neurotransmitters |
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Definition
-open either Cl- or K+ channels
- suppresses firing action pot. by making it harder for excitatory influences to depol. mem. |
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Term
| Common excitatory neurotransmitters |
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Definition
| Acetylcholine, glutamate, and serotonin |
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Term
| Common ihibitory neurotransmitters |
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Definition
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Term
| Acetylcholine receptors at Neuromuscular Jxn are? |
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Definition
| Transmitter gated ion channels |
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Term
| How are acetylcholine receptors bound by snake neurotoxin? |
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Definition
| Alpha bungartoxin binds acetylcholine receptors with high affinity and can localize receptors |
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Term
| 3 Conformations of Acetylcholine receptor. What opens the receptor? |
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Definition
1. occupied and closed (inactive)
2. unoccupied and closed
3. occupied and open
- binding of 2 acetylcholine mol |
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Term
| Persistant presence of acetylcholine in receptor does what? |
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Definition
| Inactivates or desensitizes it |
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Term
| Model for Acetylcholine Receptor structure (5) |
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Definition
1. 5 subunits to form transmem. pore
2. pore lined with ring of alpha helices
3. neg. charged SC at either side of pore, ensure only pos. ions can pass
4. Allows some Na+ and K+ and Ca2+ to pass
5. Influx of Na+ cause mem. depolarization and muscle to contract |
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Term
| T or F. Single neurons can receive input from thousands of other neurons |
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Definition
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Term
| Signals from excitatory neurotransmitter cause |
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Definition
| small depolarization known as PSP (postsynaptic potential) |
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Term
| Inhibitory neurotransmitters cause inhibitory.. |
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Definition
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Term
| Why is PSP generally not large enough to trigger AP? |
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Definition
| Because mem. of most neurons cell body and dendrites contains rela. low density of voltage gated Na+ channels |
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Term
| Combined PSP is translated into? |
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Definition
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Term
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Definition
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Term
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Definition
| glutamate receptors, 2 types- AMPA & NMDA |
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