Ion Channel Selectivity K+ Channel

The video explains the selectivity of potassium channels, focusing on why potassium ions pass through while smaller ions like sodium do not. It discusses the role of dehydration energy, ion size, and the interaction with backbone carbonyls. The structure of the channel, including alpha helices and carbonyl oxygens, is detailed, highlighting how these features facilitate potassium ion passage while preventing sodium ions from passing through.

What is the primary question raised about potassium channels in the introduction?

• Why do potassium ions move inside the cell?

• What is the role of sodium in the channel?

• Why do only potassium ions pass through the channel?

• How do potassium ions gain energy?

What is a key factor in the selectivity of potassium channels?

• The size of the cell

• The presence of sodium ions

• The energy of dehydration

• The color of the ions

Why is it easier to remove water molecules from potassium than sodium?

• Potassium is smaller than sodium

• Potassium is larger than sodium

• Sodium has more electrons

• Sodium is more reactive

What is the significance of the bond distance between potassium and backbone carbonyls?

• It varies with temperature

• It is the same as the distance to hydrating waters

• It is shorter than the distance to water molecules

• It is longer than the distance to sodium ions

How does the geometry of the hydration sphere affect ion passage through the channel?

• It changes the ion's charge

• It affects the ion's ability to fit through the channel

• It alters the ion's color

• It determines the speed of ion movement

What role do alpha helices play in the potassium channel?

• They attract sodium ions

• They block the channel

• They repel potassium ions

• They facilitate potassium movement

What happens to water molecules when potassium enters the channel?

• They are replaced by carbonyl oxygens

• They change color

• They increase in number

• They remain attached to potassium

Why is it energetically unfavorable for sodium to pass through the potassium channel?

• The channel is too narrow

• The bond distance to carbonyl oxygens is too large

• Sodium is too large

• Sodium has a higher charge

What must happen for an ion to pass through the channel?

• It must become larger

• It must change color

• Its water molecules must be removed

• It must gain energy

What is the main reason sodium does not pass through the potassium channel?

• The channel is blocked

• Sodium is too small

• The energy required to remove water is too high

• Sodium is too reactive