Lecture 68

Question 1

Selectivity of Ion channels is really determined by how well the ion is ______ by the channel, thereby displacing the water molecules that would otherwise ______ the ion, imposing a large energy barrier to the ion’s diffusion across the membrane.

Answer 1

Selectivity is really determined by how well the Ion is SOLVATED by the channel, thereby replacing the water molecules that would otherwise SOLVATE the ion.

Question 2

The activity of the Shaker Potassium channel is _____, meaning that it is inactivated soon after opening. It is also ____-gated in such a way that the S___ segment (which is positively charged) undergoes a conformational change with changes to the membrane potential. This conformational change resonates in the channel, causing it to open or close.

Answer 2

The activity is TRANSIENT. It is also VOLTAGE-gated in such a way that the S4 segment undergoes a conformational change.

Question 3

One of the key differences between Na/Ca channels and K channels is that Na/Ca channels are essentially a _____ polypeptide, whereas the K channel is comprised of _____ proteins that oligamerize in the membrane.

Answer 3

Na/Ca channels are essentially a SINGLE polypeptide, whereas K channels are comprised of MULTIPLE proteins that oligamerize.

Question 4

The _____ Receptor is an Intracellular Ca release channel that releases Ca from the Sarcoplasmic reticulum to allow for muscle contraction. It is also responsive to _____, which may be why people shake when they consume it.

Answer 4

RYANODINE

CAFFEINE

Question 5

In a ___-attached patch clamp, neither the cell membrane nor the channel is _____. With an ____-out patch clamp a segment of the cell membrane is detached (allows for manipulation of voltage across the membrane), and in a ____-cell patch the channel is blown out.

Answer 5

CELL-attached

DISRUPTED

INSIDE-out

WHOLE-cell

Question 6

____ conductance says that any time the ion channel is open, the same amount of current flows through.

Answer 6

UNITARY

Question 7

2 key features of axon Potassium channels are that they open more _____ relative to Na channels, and they don’t _____, whereas Na channels do.

Answer 7

Axon Potassium channels open more SLOWLY, relative to Na channels, and they don’t INACTIVATE, whereas NA channels do.

Question 8

Na channel inactivation involves blockage of the pore by a loop between domains ____ and ____..

Answer 8

Between domains 3 and 4

Question 9

The nicotinic ACh receptor is a ______-gated channel that is not selectively permeable, meaning Na+ and K+ pass through in relatively equal amounts.

Answer 9

Ligand