Ion Channels

Question 1

Ion Channels

Answer 1

Integral proteins that span the cell membrane and form conduits for ions to pass through the lipid bilayer

Question 2

Ion Channel Properties

Answer 2

Selective
Open and close in response to signals
Conduct ions at rapid rates

Question 3

Voltage gated ion channels

Answer 3

Respond to changes in membrane potential

Question 4

Ligand gated ion channels

Answer 4

Respond to chemical transmitters

Question 5

Mechanically gated ion channels

Answer 5

Respond to pressure or stretch

Question 6

Cation

Answer 6

Positive ion

Question 7

Anion

Answer 7

Negative ion

Question 8

Exchanger

Answer 8

Can use the energy stored in conc. gradient of one ion to transport another ion against its conc. gradient

Question 9

Hetero-oligomers

Answer 9

5 different subunits

Question 10

Homooligomers

Answer 10

6 subunits are the same

Question 11

Single polypeptide chain

Answer 11

Organized into 4 repeating motifs

Question 12

Smaller ions have a hydrated diameter that is..

Answer 12

Larger than that of larger ions

Question 13

Selectivity Filter

Answer 13

High negative site that allows na+ to pass through but not K+

Question 14

Localized conformational change

Answer 14

Ion channel only changes in one spot

Question 15

Generalized structural change

Answer 15

Ion Channel changes all along the channel

Question 16

Blocking Particle change

Answer 16

Blocking particle swings into and out of the channel mouth

Question 17

Laws of electrodiffusion

Answer 17

Laws of binding of ions to specific amino acids along the pore of an ion channel

Question 18

IV Curve

Answer 18

Rate of flow of current

Question 19

Dissociation constant

Answer 19

The ligand concentration at which current reaches 1/2 of its max value

Question 20

Simple resistors

Answer 20

Linear

Conducts ions in a constant manner at all voltages

Question 21

Rectifying Channel

Answer 21

Non-linear

Conducts ions more readily in one direction than the other

Question 22

Superfamilies

Answer 22

Ligand Gated Channel
Gap-Junction Channel
Voltage-Gated Channel

Question 23

Ligand Gated Channel Superfamily

Answer 23

5 subunits

4 transmembrane helixes each

Question 24

Gap-Junction Channel Superfamily

Answer 24

One pair of hemichannels
Each hemichannel has 6 identical subunits
Each subunit contains 4 alpha helixes

Question 25

Voltage Gated Channel Superfamily

Answer 25

Single Polypeptide chain
4 homologous motifs
Each motif has 6 alpha helixes
S5-S6 strand is P loop (Selectivity Filter)

Question 26

Ion Channel Families with P regions

Answer 26

Voltage gated K+ channel
Inward-Rectifying K+ channel
K+ channel with 2 P regions
Glutamate receptor channels

Question 27

Voltage Gated K+ Family

Answer 27

Four subunits
Each subunit has 6 transmembrane segments
Each subunit has a pore forming P-region

Question 28

Inward Rectifying K+ channels Family

Answer 28

Four subunits
Each subunit has 2 transmembrane segments
Transmembrane segments connected by a P region

Question 29

K+ channel with 2 P regions Family

Answer 29

2-4 subunits
4 transmembrane segments
2 pore forming P regions

Question 30

Glutamate receptor channel family

Answer 30

P region enters and exits on the cytoplasmic side of the membrane
4 subunits
2 transmembrane segments

Question 31

High energetic cost of K+ ions to enter bilayer is minimized by…

Answer 31

1. Inner chamber filled with polar water

2. 4 helixes provide dipole whose negative charge points toward inner chamber

Question 32

Ions in outer configuration

Answer 32

Positions 1 and 3

Question 33

Ions in inner configuration

Answer 33

Positions 2 and 4

Question 34

Chloride Channels

Answer 34

2 identical subunits each forming a selective Cl- pore
18 alpha helixes
Move Cl- against concentration gradient using H+ gradient

Question 35

Myotonia

Answer 35

Abnormal prolonged muscle contraction

Question 36

K+ channel selectivity filter

Answer 36

Parallel (Barrel Stave)

Question 37

Cl- channel selectivity filter

Answer 37

Anti-parallel