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24 Cards in this Set
- Front
- Back
permeability depends on?
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size and solubility
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which molecules are easier to diffuse?
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small hydrophobic
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protein-aided transport
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transport depends on electrochemical gradient
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permeability depends on?
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size and solubility
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2 types of transport
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passive & active
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which molecules are easier to diffuse?
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small hydrophobic
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passive transport
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involves carrier protein carries high conc. to low
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protein-aided transport
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transport depends on electrochemical gradient
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his180
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narrows diameter of channel
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arg195
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repels cations like h30+
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arrangement of dipoles in aquaporins
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2 short helices with positively charged oriented
to the pore which prevents hydrogen bonding between adjacent water molecule |
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glucose transporter
(structure, etc.) |
12 transmembrane helices, contain hydrophobic and hydrophilic residues, pose is hydrophilic and h-bonds to glucose
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diabetes insipidus
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lack of ADH receptors, collecting duct aquaporins are messed up
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primary active transport
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energy released by atp hydrolysis drives solute movement against electrochemical gradient
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secondary active transport
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energy released during movement of a solute down its gradient is used as driving force to pump other solutes against
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p-type ATPase:
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reversibly phosphorylated by ATP as part of transport cycle
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SERCA(what it does, structure, where to find?)
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transports calcium, 10 transmembrane helices and 3 globular domains:nucleotide binding, actuator, phosphorylation
found in sarcoplasmic reticulum |
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What does Ca release do?
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binds to troponin, causes tropomysin to move, exposes myosin binding site on actin
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what causes cystic fibrosis?
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loss of function of cl- transporter (which is abc) btw
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ABC transporter (structure, etc.)
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2 transmembrane, 2 nucleotide binding domains
ex. MDR, CFTR |
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ion channels
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have hydrophilic pores that have high selectivity and transport efficiency;
transport of ions occur passivel |
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K+ channel (structure, etc.)
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4 identical transmembrane subunits, have inner, outer, and pore helix, (pore has selectivity loop w/ carbonyl backbone)
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voltage gated sodium channel
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i. Structure: single, large polypeptide organized into 4 domains clustered around a
central channel ii. Features: 1. Voltage sensor: helix 4 with a high density of Arg residues; moves into membrane in response depolarization, which triggers opening of activation gate of the channel 2. Inactivation gate: a ball-like protein domain on the cytoplasmic surface of the sodium channel that blocks the channel; ensures the action potential propagates in one direction |
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acetylcholine receptors
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a. Structure: 5 subunits, each having 4 transmembrane helical segments (M1–M4)
i. Where does acetylcholine bind? On the two alpha subunits, so two Ach are required to open the channel ii. Explain how binding of Ach opens the channel. Ach binding causes twisting of M2 amphipathic helices, so that smaller, polar residues line the channe |