Module 2: Channels and Transporters

Question 1

Describe different variations of the patch clamp method and distinguish between microscopic and macroscopic currents

Answer 1

microscopic and macroscopic currents usually pretty similar, which shows voltage moderated is based on each individual channel and not just collective effort

patch clamp methods: can monitor one part of membrane, tear it out, turn it around, and affect the voltage to see how it reacts

Question 2

recall the functional states of voltage-gated Na+ and K+ channels

Answer 2

Na+ opens quickly but then closes quickly, 3 channels open, last one closes behind it, K+ opens slowly then closes when it polarizes it again

Question 3

describe how ion selectivity is achieved for K+ channels and recall the importance of voltage sensing and pore domains

Answer 3

proteins joined so there’s selectivity filter
- K+ dehydrated upon entry, electrostatics repulsion push it through
- pore small so can only fit K+

voltage sensor of K+ channels
- A-helix is attracted to negative charge, hyperpolarization pulls voltage sensor inward, depolarization pushes sensor outwards

Question 4

describe structural differences between Na+, Ca2+, and K+ channels and diverse properties of different types of K+ channels

Answer 4

K+ each subunit encoded by a different gene
NA+ and Ca++ one gene encodes four subunits