Week 5 - Channel Physiology - Fitzakerly

Question 1

Do all channels have selectivity, gating and inactivation mechanisms?

Answer 1

ALL channels have selectivity and gating

ONLY SOME channels have inactivation

Question 2

List key differences between ion channel and transporters:

Answer 2

Ion channels:
passive, direct connection between intra and extra cellular space, only move ions, VERY fast

Transporters:
Passive or active, with or without concentration gradient, never have a direct connection between inside and outside, move small ions or larger molecules, not as fast as ion channels

Question 3

A cell with no aquaporins is places if a hypo tonic solution. What happens?

Answer 3

Nothing. NO lysis if no aquaporins present for osmosis.

Question 4

What are the 4 types of channel gating?

Answer 4

Leak: Always open (neurons)
Mechanical: (sensory)
Ligand: (Bound chemical changes conformation of channel)
Voltage-gated: In excitable cells

Question 5

Why would it be unlikely for both Na and Cl to pass through the same channel?

Answer 5

Generally channels are either all cation, all anion, or one specific ion, NOT an anion and a cation

Question 6

List 4 ways that an ion channel can open

Answer 6

membrane stretch
depolarization
ligand binding
random changes in position of channel gate

Question 7

Are ions more likely to leave or enter a cell through a channel?

Answer 7

Neither. They are bidirectional so it all depends on concentration and electrical gradients.

Question 8

Rank the 4 major ions in order of extracellular ion concentrations:

K, Na, Cl, Ca

Answer 8

Na+ > Cl- > K+ > Ca2+

Lots of Na outside the cell, Cl is inbetween, K+ most abundant intracellular ion, Ca is the least abundant intra and extracellularly