BIOL211 L3

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  • Created by: Katherine
  • Created on: 22-04-17 19:04
What are primary pumps powered by?
ATP
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What are the 3 different types of pumps?
P type ATPases, ABC superfamily, V type protein pump, F type proton pump
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What do P type ATPases consist of?
large a catalytic subunits of up to 200 kDa
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What do P type ATPases pump?
Cations (not anions)
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What are P type ATPases inhibited by?
Micromolar amounts of orthovanadate
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What happens to the P type ATPases during ATP hydroylsis?
ATP donates its y phosphate to a conserved aspartae during cation pumping forming a phosphorylated intermediate
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Give an exxample of a P type pump:
Na/K ATPase in animal cells
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Discuss the Na/K ATPase pump:
Located on the PM of animal cells (3 isoforms). Stoichiometry of 3Na+:2K per ATP hydrolysed. Function of house keeping functions.
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What is the function of Na/K ATPase pump?
Maintains high K+ and low Na+ in the cytosol - important in action potential generation. Maintain N electrochemical potential - Na+ coupled transport
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What is the structure of Na/K ATPase pump?
Composed of 2a and 2 B subunits. It is inhibited by ouabain
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Give another example of an ATP pump, for fungal and plants
H+ ATPase
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Where is the H+ ATPase located?
On the PM of all plants and fungal cell
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What are the substrates of H+ ATPase?
Stoichiometry of 1H+ per ATP hydrolysed
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What is the function of H+ ATPase?
To expel excess H+ produced during metabolism, generate H+ electrochemical gradient which is used to drive H+ coupled transport. Maintain engative tranmembrane voltge. Regulate cytosolic pH
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What is the H+ATPase structure?
Composed of 1a subunit
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What is the name of the sarcoplasmic reticulum membrane pump in muscle cells?
Ca2+ ATPase (SERCA)
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What is the location of SERCA?
The sarcoplasmic reticulum of tubules in the muscle cell cytoplasm forming stores of Ca2+
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What are the substrates associated with SARCA?
2Ca2+/ATP
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What is the function of SERCA?
To restore low cytosolic Ca2+ after muscle contraction
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What i the structure of SERCA?
1 a subunit (3 isoforms)
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What is an inhibitor to ERCA?
Thapsigargin
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Where is a Plasma membrane Ca2+ ATPase found? (PMCA ATPase)
Fungal, plant and animal PMs
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What are the substrantes of PMCA ATPase?
Stochiometry of 1 - 2 Ca2+
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What is the function of PMCA ATPase?
Maintain low cytosolic Ca2+ - high cytosolic Ca2+ is cytotoxic. Central role in cell signalling.
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What is the structure of PMCA ATPase?
1 a subunit
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Where is the Gastric muscosal H+/K+ ATPase?
PM of gastric epithelium cells (stomach wall)
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What are the substrates of Gastric muscosal H+/K+ ATPase
2K:2H+ per ATP hydrolysed
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What is the function of the Gastric muscosal H+/K+ ATPase?
H+ secretion in to the lumen of the stomach - acidic stomach
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What is the structure of the gastric muscosal H+/K+ ATPase?
2 a and 2 b subunits
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Which other pump is the gastric muscosal pump closely related to?
Na+/K+ pump
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What is the structure of P type ATPases?
4 TMS domains and 4 stalk regions on the N terminus and 6 TMS domains and a 5th stalk region on the C terminus.
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How does P type pump mediated ion transport work? 1
High affinity binding of 3Na+ ions on the E1 side at the Na+ binding site. Binding of ATP phosphorylation of aspartate. Conformational change, outward transport of Na+.
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Once the Na+ is dossociated in the E2 side, what happens?
Binding of K+ on the E1 side. Hydroylsis of aspartyl phosphate. Conformational change, inwards transport of K+. Dissociation of K+ ions into the cytosol.
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Conformational changes induce changes in cation binding to allow:
Binding of ions at low concentration (i.e binding of extracellular K+ or cytosolic Na+) Dissociation of ions at high concentrations (i.e. release of Na+ and K+ to outside and cytosol respectively)
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What are CPx pumps?
They pump toxic and nutrient metals (e.g. cu,pb, cd and zn)
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Where are CPx pumps deficient?
Menkes disease (systemic copper deficiency) and wilsons disease (excessive copped accumulation in the liver)
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What are the structural differences between CPx and P type pumps?
CPx have 2 extra TMS domains on N terminus, cysteine repeats, conserved cpx motif, have a histidine proline region in the c region, there are fewer TMS domains in the c terminus
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What is the function of V type pumps?
Operate almost exclusively as H+ATPases on intracellular membranes of eukaryotic cells
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Where is the V pump found?
ER and SR membrane
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Why does the V type pump have a chloride channel?
For every proton that goes in, a chloride does too - that way the positive charges are balanced and you can still get a low ph.
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What is the structure of the V type pump?
3 A and 3 B complex at the botom, generates the torque in the D subunit to rotate the ring of 6 c subunits
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What are ABC transporters?
Use the energy associated with hydrolysis. They move lots of different types of substrate
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What is the clinical importance of ABC transporters?
Cystic fiborsis, and MDR transporters
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What is the structure of ABC transporters?
They have 6TMS domains and then Atp binding and then 6 TMS again.
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What is the mechanism of action for the ABC transporter?
The lipid soluble molecule first dissolbes into the cytosolic facing leaflet of the plasma membrane where it binds to the MDR1 protein (chamber).
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What is the mechanism of action for the ABC transporter? 3, 4,5
Powered by ATP hydrolysis, the substrate molecule is flipped into the exoplasmic leaflet of the plasma membrane. The substrate molecule diffuses into the extracellular space.
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Summary: What are the substates of P type?
H, Ca2+, K+ and Na+ (CPx type = heavy metals)
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What is the structure of P type?
Large a subuni which is phosphorylated. Range of functions (e.g. establisihng driver on electrochemical gradients)
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What is the cellular location?
PM, SR or Er
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What is the substrate of V type?
H+
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What is the structure?
Multiple transmembrane and cytosolic subunits. Etablished H+ electrochemcal gradients.
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Where is the V type located?
Vacuolar (plants), lysosomes and synaptic vesicles (animals)
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What are the substrates of ABC type?
Varied
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What is the structure of ABC type?
2 sections of transmembrane spanning domains and 2 ATP domains - range of physiological functino
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Where is the cellular location of ABC type?
Found in all membrane types
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Card 2

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What are the 3 different types of pumps?

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P type ATPases, ABC superfamily, V type protein pump, F type proton pump

Card 3

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What do P type ATPases consist of?

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Card 4

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What do P type ATPases pump?

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Card 5

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What are P type ATPases inhibited by?

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