Membrane Poential Mount Vernon School District膜电位弗农山校区.pptVIP

Membrane Potential 2012-13 QUICK REVIEW This is an example of what kind of transport? Passive (Simple Diffusion) This is an example of what kind of transport? Primary Active Transport Membrane Potential The voltage across the plasma membrane that is the result of a difference in electrical charge inside vs outside the cell It is called potential b/c it represents stored electrical energy that can be used to do work at some future time Measured in millivolts (mV) Requires active transport (Na+/K+ pump) to maintain Setting up the Membrane Potential Certain anions (-charged particle) are confined to inside of cell They attract cations (+ charged particles) inside What effect might all these solutes inside the cell have on the water outside the cell? Draws water in Causes swelling possibly lysis (bursting) of cell Setting up the Membrane Potential (cont.) Inflow of water stimulates the Na+/K+ pump Pumps 3 Na+ out and 2 K+ in Is this active or passive transport? What is the net effect on the cell? More + is leaving What’s so great about the Na+/K+ pump? It sets up a steep concentration gradient across the cell membrane where there is a lot more Na+ outside and more K+ inside. This is potential energy Na+ wants to come in What’s so great about the Na+/K+ pump? (cont.) Heat production Thyroid hormone stimulates cells to produce more Na+/K+ pumps in winter months –why? Heat is generated when the pump consumes ATP This compensates for the heat we lose to the cold environment * ATP - ADP + Pi Proteins - Phosphates - + - The cell membrane is more permeable to K+ (compared to Na+) In a normal leaky cell would K+ leak in or out? Would Na+, leak in or out? Overall, 3 Na+ leak in and 2 K+ leak out. Is this active or passive transport? The Na+/K+ pump controls the leak… and does exactly opposite 3 Na+ out and 2K+ in Why do we use ATP for this? ATP - ADP + Pi Less K+ leaks out because it is attracted to the negative charge inside the cell More Na+ leaks in because it