Chapter 4 Study Questions (Part 2)

Question 1

what are the characteristics of an aquaporin that makes it possible to selectively move water across the plasma membrane?

Answer 1

interior compartment: positive pushes out, only single file H2O molecules get through.

Question 2

what determines what water does in an aquaporin?

Answer 2

solute concentration

Question 3

what are leak channels?

Answer 3

no gate/closure, always open

Question 4

what are gated channels?

Answer 4

not always open

Question 5

what are the different types of gated channels?

Answer 5

1. voltage gated
2. ligand/chemically gated
3. mechanical/stretch gated

Question 6

____ opens a _____-gated ion channel that then opens a ______-gated channel

Answer 6

ligand opens a ligand-gated ion channel that then opens a voltage-gated channel

Question 7

does a typical cell have more Na+ or K+ channels?

Answer 7

fewer Na+ leak channels than K+

Question 8

role of Na+/K+ ATPase pumps?

Answer 8

actively pump Na+ out and K+ into the cell to counter the leak channels

Question 9

why do you think a typical cell cannot have as many Na+ leak channels as K+ leak channels?

Answer 9

cell wants to maintain (-) inside.

Na+ leaks (+) in

K+ leaks (+) out

you want less (+) leaking in, not more! and more (+) leaking out