Lec 8 Flashcards
All channels are made up of a-subunits that contain __ (number) transmembrane a-helicies
6
How many total a-transmembrane helicies exist in a Na+ channel?
6 trans.mem. x 4 domains = 24 per subunit
24 trans.mem per unit x 1 = 24 to make a channel.
How many total a-transmembrane helicies exist in a K+ channel?
6 trans.mem. x 1 domain = 6 per subunit
4 subunits per channel x 6 = 24 per channel
How many a-subunits are needed to make a Na+ channel?
1
How many a-subunits are needed to make a K+ channel?
4
What is defined as “subunits that influence the channel’s distrubution, voltage, dependence, and inactivation. “ ?
Accessory Subunits
What are the 2 KEY structural elements in a ion channel?
S4 segment
and
The P Region
What is defined as “positively charged residues every 3rd amino acid for voltage sensing” ?
S4 segment of a channel
What structure is defined as “dips into the membrane but does not cross it… is used for ion selectivity.” ?
The P region of a chennel
Why do all channels have similar structural components?
Though to have evolved from a common ancestor channel biollions of years ago.
Rank the following channels from most ancient to least anceint.
Ca2+
K+
Na+
K+
Ca2+
Na+
Rank these channels from highest diversity to lowest diversity.
Ca2+
K+
Na+
K+
Ca2+
Na+
How did a single a-subunit K+ channel become a 4 a-subunit Ca2+ channel?
by genetic mechanisms of internal duplication and specialization.
K –> Ca –> Na
Na+ channels in different species all do the same thing and have similar properties.
T or F?
True
Na+ channels are concentrated in the _________ region of the neuron, which makes this the most likely place for the triggering of ___________.
Axon Hillock
Action potentials
Voltage dependence of Na+ channels is highly dependent on the concentration of ____ (Ca2+ , K+ , Cl-) ions in extracellular fluid.
Ca2+
Low Ca2+ levels in extracellular fluid shift the probability curve in a more ______ (positive/negative) voltage.
negative
Low Ca2+ levels leads to hyperexcitability or hypoexcitability?
hyperexcitability
High Ca2+ levels in extracellular fluid shift the probability curve in a more ______ (positive/negative) voltage.
positive shift
Hyperexcitability occurs from shifting the Po curve to a more negative threshold.
T or F?
True
more negative threshold means its easier to create an AP
Local anesthetics block ___ (ion) channels.
Na+
Cocaine is a Anesthetic and blocks Na+ chennels. 3 alternate forms of this drug are:
- P_______
- L_______
- T_______
Procaine
Lidocaine
Tetracaine
Local Anestheic blocks, such as Cocaine , are dependent on 2 variables. What are they?
use dependent (stimulation frequency)
time depedent
Cocaine is most likely to block OPEN Na+ channels.
T or F?
True
What is defined as “mutated Na+ chennels lead to human disease.” ?
Channelopathies
mutated domains (3 and 4) is a from of …
channelopathy
