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34 Cards in this Set
- Front
- Back
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What type of molecules do not require a transport mechanism?
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lipid-soluble molecules, typically hydrophobic
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What type of barrier is the cell membrane?
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selectively permeable
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What is passive transport? active?
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Passive - 1 molecule using a channel or transporter and goes down its concentration gradient
Active - Requires energy from either ATP or symport or antiport of 2 or more molecules |
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What are 3 ways of driving active transport? Why is active transport required?
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Coupled, ATP, light (bacteria)
moving a molecule against the gradient |
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What is the term for maintenance of physiological variables within precise limits?
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Homeostasis
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What is the positive Ca feedback system in T cells?
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Ca released through IP3R -> Ca binds IKCa1 which releases K+ from the cell -> creates an electromagnetic gradient -> allows CRAC channel to let more Ca into the cell
That will eventually activate a promoter |
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What is a CRAC channel? Once opened when does it close?
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Ca release-activated Ca channel
When intracellular [Ca] reaches a certain level, it closes. called negative feedback |
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What moves molecules faster a channel or a transporter?
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Channel
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What do symport and antiport do?
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use one molecule with its concentration gradient to push another molecule against its concentration gradient, active transport
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Explain Na, K, Glu interactions in lumen of intestine.
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1. Symport of Na and Glu, Na with the gradient, Glu against. from the lumen
2. Antiport of Na and K. K travels with its gradient into the cell to push Na out of the cell into the paracellular space 3. Glu leaves the cell as a uniporter into the capillary |
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What are the three types of ATP pumps and describe them?
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1. P-type - uses phosphate and energy from ATP to move ions out of cell
2. F-type (V-type) proton pump - makes ATP from ADP & Pi 3- ABC transporter - hydrolyzes 2 ATP to move the two sides of the pump |
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What is an example of a p-pump? the one used in t-cells to get 2 Ca into the cell?
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SERCA pump. moves 2 Ca+
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What is the most common CFTR mutation in humans?
(Cystic fibrosis something) what is the channel regulated by? what does the mutation mess up? |
delta F508
enzyme activity protein folding |
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What domain is unique to CFTR?
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R domain
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What is the difference between channel activity in wild type CFTR and in CF mutants? graphed current/s
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Wild type has many peaks so plentiful chloride release
mutants not nearly as many peaks so chloride release is minimal |
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What is the biggest thing targeted by current drug therapies?
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receptors
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What can control the gates of ion channels?
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membrane potential, neurotransmitters, second messengers (ligands), environment (hot/capsaicin, cold/menthol, stretch/shear)
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What is a non-selective ion channel?
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channel that would allow several ions to pass
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What is a VSD and PD for gating mechanisms?
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VSD: voltage sensing domains
PD: pore domain |
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How do voltage sensing domains work?
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They have a series of positive amino acid residues (Arginine) that reside in the membrane. When the membrane potential changes, they are forced outside the membrane, which causes a conformational change of the pore domain
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What is the ball and chain model?
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When the membrane is polarized, the channel is closed.
Depolarized - channel is open, but can be inactivated by sticking the ball (NH2) into the open channel. |
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Why is ion selectivity important? What are 2 key factors to selectivity?
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Allows selective transport
Size and shape |
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What are common amino acids in coding for pore loops of channels?
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TTVGYG
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What makes a K+ channel selective?
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In the filter, it makes 4 transient bonds which give the energy to break bonds with water.
A Na+ molecule can't form all the same bonds so it is usually pushed out of the filter |
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What provides the selectivity of potassium channels?
of Calcium channels? |
backbone carbonyl groups
Ca: Glu/Asp side chains |
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What was the point mutation on the Orai of CRAC? and what did it do?
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It was changing a glutamic acid into a aspartic acid.
Altered the functionality of the ion filtering site such that Ca flows out of the cell (outward rectifying) instead of into the cell (inward rectifying) |
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What is the simplest voltage clamp? what does it allow?
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A single pipette with no feedback amplifier
single channel resolution at millisecond time scale |
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Ion channel configurations: 1. Cell-attached, 2. inside-out, 3. outside-out, 4. whole-cell, 5. perforated-patch
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1. pipette is sealed on the cell and left attached
2. pipette removes a channel with a bubble putting into the pipette 3. pipette removes a bubble with the bubble facing away from the pipette 4. pipette creates a gap straight into the cytoplasm of cell 5. modified cell-attched with stuff in the pipette |
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What is a calcium buffer called, and what are two examples?
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EGTA and BAPTA, chelators
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What are two properties of calcium indicators? And what can fluorescence be used to do?
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They need to bind Ca and to be visible so give off fluorescence
Find concentrations |
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What percentage of the human genome do ion channels account for?
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1.3%
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What are the 4 classes of mammalian K+ channels?
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One Pore - 1: 2 transmembrane segments(2T). 2: 6T
Two pore - 1: 4T 2: 8T |
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What ion channelopathies look like in the:
1: CNS 2: Heart 3: Skeletal muscle 4: Vascular smooth muscle |
1: Seizures, ataxia, migraine
2: Arrhythmia 3: paralysis, myotonia, paramyotonia, hyperthermia 4: hypertension |
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What ion channelopathies look like in the:
1: Renal 2: lung 3: Endocrine 4: T cells |
1: electrolyte abnormalities
2: cystic fibrosis 3: diabetes 4: severe combine immune deficiency |
