channels and transporters

Question 1

patch clamp

Answer 1

sensitive voltage clamp methods that permits the measurement of ionic currents flowing through individual ion channels
inside-out important for studying the influence of intracellular molecules on ion channel function
outside-out important for studying how channel activity is influenced by extracellular chemical signals such as neurotransmitters

Question 2

what triggers channel opening

Answer 2

ligand, voltage, mechanical force, temp

Question 3

the response characteristics of a neuron are largely determined by

Answer 3

the type and distribution of ion channels it expresses

Question 4

Na+ and Ca2+ channels are composed of

Answer 4

• 4 repeating subunits
• each subunit has repeating motifs of 6 membrane-spanning regions
• beta subunits
• 2 of the membrane-spanning domains form the channel through which ions pass
• 1 domain has a loop attached that confers ion selectivity
• 1 domain is a helix with special distribution of positive and negative charges serves as the voltage sensor

Question 5

Na+ selectivity

Answer 5

Na channels contain a selective filter
it is hypothesized to be a gap with a binding site on one end that attracts the positive ion

Question 6

K+ selectivity

Answer 6

the negative charges on one part of the protein help strip the water molecules from the K+ ion, the pore is large enough the the naked K+ ion can pass
Na+ is too small for this to work

Question 7

primary active transport

Answer 7

use ATP as an energy source

Question 8

secondary active transport

Answer 8

use the flow of one type of ion down its gradient as the energy source

Question 9

steps on the sodium potassium pump

Answer 9

1 Na+ binding (on inside)
2 phosphorylation
3 conformational change causes Na+ release to outside and K+ binding
4 dephosphorylation-induced conformational change leads to K+ release on inside

Question 10

electrogenic

Answer 10

generates membrane potential
Na/K pump - 3 out, 2 in