Gates and Channels

Question 1

• Ion channels:
  1. ) Kv Channel: Structure? S4 does what? S5,S6 and P do what? K:Na selectivity?
  2. ) Cav and Nav channel: structure? Domain made of? S4? Linker? Ca:Na selectivity? Na:K selectivity?
• Pentamer Ligand gated channels: Selective for? structure? Ex? (3) Na:K selectivity?

Answer 1

1. ) 6 alpha helices S1-S6; link b/n S4 and S5; + charged residues every third to sense voltage; selectively filter; 10,000:1
2. ) 4 domains; S1-S6 each; activation gate; inacitvation gate; 3000:1; 12:1
   - Cl- or cations; 4 transmembrane a helices; 1.3:1; AchR; GABAr; GlyR

Question 2

• Terameric ligand gated channels: Number of subunits? alpha helices/sub unit? Ex?
• CLC Chloride Channels: Structure? Ex?
• Aquaporins: Structure? Ions?
• Ways for selectivity? (4)
• Primary active Transport?
• Secondary Active Transport? Prevalnce? 2 basic types?

Answer 2

• 4; 3; Ionotropic glutamate receptors
• dimer; H+/Cl- exchangers
• Tetramer with 4 water pores; excluded
• Size, charge, dehydration, multiple binding sites
• ATP does work
• Na+ leak into cell to do work; much more common; cotransporter; antiporter

Question 3

• Electrogenic secondary active transport?
• Non- electrogenic?
• “Non existant” H+/K+ exchanger: Clinical evidence for this? (2) How does it probably work in reality?
• How do cells concentrate glucose inside them? (2)

Answer 3

• One cycle produces net charge difference
• Don’t change net charge difference of membrane
• Infusing K+ leads to acidemia; infusing K+ leads to hyperkalemia; prob. has pumps working in parallel
• Glucose gets phosphorylated once it enters the cell; glucose transporters usually sequestered in cell vessicles until insulin signals the cell to take up glucose