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37 Cards in this Set
- Front
- Back
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Na+ & K+ Pump is an ATPase how many ions does it pump in which direction? What causes the conformational change? When does ATP bind and release? what type of port is it? |
Pumps 3 Na+ out, 2 K+ in per ATP, against their concentration gradient 1. 3Na+ binds in un-P state 2. ATP binds, Autophosphorylation triggers conformational change 3. ADP dissociate, (still P) --> binding site opens --> Na+ leaves, 2 K+ enters 4. dephosphorylation --> K+ released inside cell type: active antiport |
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K+ and Na+ gradient can be used as source of free E, give an example |
Na+ down gradient, glucose up gradient both into the cell |
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Describe glucose is reabsorbed in epithelial cells. name the 2 regions in epithelial cell which part is active transport, which is passive, type of port? what drives the active transport |
Apical and basolateral plasma regions Apical region: ACTIVE symport driven by Na+ gradient Basal region: Passive uniport of glucose Na+ & K+ pump |
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What is primary active and secondary active |
Primary active : ATP driven Secondary active: use of gradient |
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Ion channels: 4 types of gating |
1. Voltage gated 2. ligand gated (extracellular) 3. ligand gated (intracellular) 4. mechanically gated |
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Ion channels: passive or active transport? what is a selectivity filter give examples of K+ channel |
Passive only - "Facilitated diffusion" (10^5 times faster than transporter) Selectivity filter: ions transiently (ชั่วคราว) contact channel pore sidechain lining K+ channel: selectivity filter work in TETRAMER, hydrophillic sidechains make K+ ions think they are still in water with hydration shell Na+ can't go through because too small, can't remain comfortably charge-shielded |
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Clicker: Why is ion channel so much faster than a transporter? |
1. Diffusion is much faster, don't need conformational change 2. pore allows unhindered conformational change 3. more than one can occupy simultaneously |
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Resting potential what id the difference between steady state and equilibium |
potential of -70mV there is a CONSTANT FLOW with NET FLOW = 0 Steady state: needs INPUT of E to maintain Equilibrium: don't need E |
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Membrane is a capacitor, how is this accomplished? which part is + and - ? |
the use of Na+&K+ ion pumps, ATPs are burning to keep this gradient +++++ OUTSIDE +++++ =================== - - - - - - INSIDE - - - - - - - |
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3 distinct states of voltage gated channels |
1. Closed 2. Open 3. Inactivated - N-terminus of the channel protein blocks the flow rapidly |
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4 phases of the Action potential |
1. Resting potential - steady state, balance in K+ pump and channel 2. Depolarization phase - as potential reaches the threshold level Na+ flows into cell through ligand-gated channel 3. Repolarization phase - Voltage-gated K+ channel opens, K+ rush out of cell 4. Undershoot - "refractory period" channels are inactivated and wait until return to closed conformation |
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Why does action potential go in one direction only? |
because need time in the refractory period |
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How does neurons propagate action potentials? |
through waves of voltage-gated channel activation Presynaptic ending --> as action potential reaches, V-Gated Ca2+ channels open, release neurotransmitter (signals) into the synapse Postsynaptic dendrites --> ligand(neurotransmitter) gated Na+ channels activated, creates a new action potential |
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Intracellular compartments: Nucleus |
contains main genome, DNA and RNA synthesis |
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Intracellular compartments: Cytosol |
protein synthesis
glycolysis (glucose -->pyruvate) AA & nucleotide synthesis |
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Intracellular compartments: Endoplasmic reticulum (ER) |
synthesis of
membrane proteins secreted proteins lipids |
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Intracellular compartments: Golgi Apparatus |
covalent modifications of proteins from ER,
sorting protein transport to other cellular parts put lipids into membrane |
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Intracellular compartments: Mitochondria and chloroplasts (Very general description) |
ATP synthesis
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Intracellular compartments: Lysosomes |
degradation of intracellular organelles & material from outside
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Intracellular compartments: Endosomes |
sort proteins received from:
endocytic pathway golgi apparatus |
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Topology of the ER lumen |
is topologically equivalent to outside of the cell |
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Cis golgi trans golgi types of vesicle |
cis - receive proteins trans - release proteins in transport vesicles secretory vesicles - to outside of cell transport vesicles - within different organelles |
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How does golgi know where to send proteins to? |
through the SIGNAL sequence in the protein, these direct the transport whether they should be sent to import to ER return to ER outside the cell import to nucleus export from nucleus |
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Structure of the nuclear pore complex what is perinuclear space |
nuclear membrane is a DOUBLE bilayer, perinuclear space = ER lumen the pore allows both simple DIFFUSION: small AA can still fuse when pore closes ACTIVE TRANSPORT: Macromolecules |
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Nuclear localization Sequence (NSL) what complex help them with transport |
short AA sequence can appear anywhere, are bound and carried through pore by Nuclear import receptors |
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NUCLEAR TRANSPORT How does the active transport mechanism through nuclear pores work? What is used in cyclic enzyme activation and inactivation |
phosphorylation using monomeric GTPases Ran-GDP/GTP is attached to the NIR (nuclear import receptors) OUTSIDE cell: high Ran GDP because Ran-GAP de-P the Ran GTP---> Ran GDP ================== INSIDE: high ran-GTP because Ran-GEF puts Ran-GTP onto the receptors |
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MITOCHONDRIAL TRANSPORT what are the important proteins used to help with unfolding/folding which complexes are outside/inside the mitochondria |
Chaperones are used to unfold protein to get through the pore, and re-fold when inside TOM complex is outside, where it's receptor protein binds to the signal sequence of protein being imported. TIM23 complex is inside, chaperone refolds protein, signal peptidase cleaves signal sequence --> mature protein ready to function |
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Comparison of nuclear and mitochondrial transport signal sequence |
Nuclear: anywhere, short and + charged
Mito: N-terminus amphipathic alpha helix |
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Comparison of nuclear and mitochondrial transport Fate of signal sequence |
Nuclear: unchanged after transport Mito: removed by signal peptidase Chloroplast: happen twice (have 2 signals) because have 2 inner membranes |
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Comparison of nuclear and mitochondrial transport Energy |
Nuclear: GTP hydrolysis Mito: ATP hydrolysis, proton gradient |
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Comparison of nuclear and mitochondrial transport conformation of protein |
Nuclear: kept folded Mito: unfolded through pore and refolded |
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Comparison of nuclear and mitochondrial transport type of transport mechanism |
Nuclear: Gated transport Mito: transmembrane |
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Translocation of protein into the ER can happen in 2 ways |
co-translational or post translational |
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what does a Signal Recognition Particle do? |
target ribosomes to ER surfaces for translation of cotranslation translocation |
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The cellular functions of ER |
- Entry point of secretory pathways - establishes the protein orientation in the membrane (with lumen) - site of lipid biosynthesis - Initiation site of N-linked glycosylation (connecting proteins and functional groups) -Intracellular storage of Ca2+ - detoxification: blood goes to liver and inside the ER has cytochrome P450 enzyme |
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Differences between rough and smooth ER |
smooth (spaghetti) rough (pancake) - has polyribosome bounded signal recognition particle (SRP) --> translocation channel---> released into lumen OR stay in the membrane if it is a TMP |
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Sequences associated with the rough ER protein synthesis&translocation |
Start transfer sequence - stick me into the pore, get cleaved and degraded after Stop transfer sequence - let me stay in the membrane |
