BIOL 4610 1st Edition Lecture 11 Outline of Current Lecture 1. V-Class pumps2. Hydration shell of K+3. Aquaporins4. Co-transport5. Trans-epithelial TransportCurrent LectureV-class Pumps- Are all H+TPases- Maintain electric potential11.4. Nongated Ion Channels and the Resting Membrane Potential – Na, K, Cl, water (aquaporin) - The channels generate an electric potential- Most are gated, some are always open- Have K channels that are open- Used for acidification- K+ higher inside the cell, so flows freely to the outside (along conc gradient)- This generates an electrical difference along the membrane à -70mV An example of a nongated channel is the K + channel: - Ion channels have selectivity filter, this restricts what can pass thru- Since it’s moving K+, must have negatively charged AA’s- Must be a size selection as wellThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Hydration shell of K+ has the same geometry as the channelThe hydration cell matches that of K+This means all ions are bound by water molecules. They don’t just exist as the ion, they are in a water shell surrounding it.K+ and Na have four water molecules surrounding themWe must make K+ energetically favorable for it to pass thru the channelWe remove the water molecules so it can pass thru the channel just as a K+ ionGeometry of pore/channel mimics that of its hydration shellAquaporins – channel that moves water- Partial charges for O and H- Size of opening is .28nm (slightly larger than H2O)- Help regulate flow of water, always flows (using aquaporins) where solute concentration is highest11.5. Cotransport by Symporters and AntiportersThe change in free energy can power movements in opposite direction. 1 molecule moves down its gradient so that it moves a 2nd molecule up a gradient (without the use of ATP)If we move Na down its conc gradient, we can capture 1.45 kcal/mol of energy.Also a difference in electrical potential, we are partially neutralizing the charge by moving na inside cellSO capturing enough energy to move another molecule up its gradient11.6. Transepithelial TransportSome epithelial cells are polarized.- Cells that line surfaces- Skin, intestines, - Sidedness to cells- Tight junctions > Prevent movement of molecules around cell, and make sure protein transporters can’t move from one side of cell to
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