Lec 8

Question 1

All channels are made up of a-subunits that contain __ (number) transmembrane a-helicies

Answer 1

6

Question 2

How many total a-transmembrane helicies exist in a Na+ channel?

Answer 2

6 trans.mem. x 4 domains = 24 per subunit

24 trans.mem per unit x 1 = 24 to make a channel.

Question 3

How many total a-transmembrane helicies exist in a K+ channel?

Answer 3

6 trans.mem. x 1 domain = 6 per subunit

4 subunits per channel x 6 = 24 per channel

Question 4

How many a-subunits are needed to make a Na+ channel?

Answer 4

1

Question 5

How many a-subunits are needed to make a K+ channel?

Answer 5

4

Question 6

What is defined as “subunits that influence the channel’s distrubution, voltage, dependence, and inactivation. “ ?

Answer 6

Accessory Subunits

Question 7

What are the 2 KEY structural elements in a ion channel?

Answer 7

S4 segment

and

The P Region

Question 8

What is defined as “positively charged residues every 3rd amino acid for voltage sensing” ?

Answer 8

S4 segment of a channel

Question 9

What structure is defined as “dips into the membrane but does not cross it… is used for ion selectivity.” ?

Answer 9

The P region of a chennel

Question 10

Why do all channels have similar structural components?

Answer 10

Though to have evolved from a common ancestor channel biollions of years ago.

Question 11

Rank the following channels from most ancient to least anceint.

Ca2+

K+

Na+

Answer 11

K+

Ca2+

Na+

Question 12

Rank these channels from highest diversity to lowest diversity.

Ca2+

K+

Na+

Answer 12

K+

Ca2+

Na+

Question 13

How did a single a-subunit K+ channel become a 4 a-subunit Ca2+ channel?

Answer 13

by genetic mechanisms of internal duplication and specialization.

K –> Ca –> Na

Question 14

Na+ channels in different species all do the same thing and have similar properties.

T or F?

Answer 14

True

Question 15

Na+ channels are concentrated in the _________ region of the neuron, which makes this the most likely place for the triggering of ___________.

Answer 15

Axon Hillock

Action potentials

Question 16

Voltage dependence of Na+ channels is highly dependent on the concentration of ____ (Ca2+ , K+ , Cl-) ions in extracellular fluid.

Answer 16

Ca2+

Question 17

Low Ca2+ levels in extracellular fluid shift the probability curve in a more ______ (positive/negative) voltage.

Answer 17

negative

Question 18

Low Ca2+ levels leads to hyperexcitability or hypoexcitability?

Answer 18

hyperexcitability

Question 19

High Ca2+ levels in extracellular fluid shift the probability curve in a more ______ (positive/negative) voltage.

Answer 19

positive shift

Question 20

Hyperexcitability occurs from shifting the Po curve to a more negative threshold.

T or F?

Answer 20

True

more negative threshold means its easier to create an AP

Question 21

Local anesthetics block ___ (ion) channels.

Answer 21

Na+

Question 22

Cocaine is a Anesthetic and blocks Na+ chennels. 3 alternate forms of this drug are:

1. P_______
2. L_______
3. T_______

Answer 22

Procaine

Lidocaine

Tetracaine

Question 23

Local Anestheic blocks, such as Cocaine , are dependent on 2 variables. What are they?

Answer 23

use dependent (stimulation frequency)

time depedent

Question 24

Cocaine is most likely to block OPEN Na+ channels.

T or F?

Answer 24

True

Question 25

What is defined as “mutated Na+ chennels lead to human disease.” ?

Answer 25

Channelopathies

Question 26

mutated domains (3 and 4) is a from of …

Answer 26

channelopathy