Week 6 Bollough Lecture 13 Flashcards
How does kcsA transport K+?
There are 4 regions for K+ to bind inside the protein, 2 of them can be occupied at the same time. Only dehydrated ions can be transported, hydrated ions are too big to fit
How are positive ions are attracted to the channel?
There is a cavity inside which has a hydrated ion which attracts positive ions, the dipole of the half helix (pore helix) also attracts positive ions.
Why are K+ ions more permeable than other positive ions?
If the radius of a molecule is too large, it cannot fit in the narrow pore,
a) What about smaller positive ions like Na+?
b) Na+ has a more negative hydration free energy, this means it requires more energy to remove the water molecules. Even though there are more eater molecules that can be bound to K+ than in Na+. This desolvation says that the energy for dehydrating an Na+ ion larger than the energy produced by the K+ channel site.
How does the ion passage work?
It is eased by electrostatic repulsion from the queue of K+. There are 4 sites but only 2 can be occupied at a time. As the ions move, the pore slightly changes shape to ease passage pathway.
