8. The cartoon at the right depicts a hypothetical cell that has a Lit-K+ ATPase (shown as the filled circle with arrows). The cell also contains Lit and K* channels. The membrane is three times more permeable to K* than it is to Li*. The following are the steady state concentrations of Lit and K*: [Li*Jout [Li*]in = 5 mM = 4 mM Lit = 100 mM ADP + P ATP [K*Jout [K*]in Temp = 10°C Assuming that the Vm is produced only by the diffusion of Li and K*, calculate the Vm. = 80 mM

Your friend has made an artificial membrane to study ion concentration gradients in a laboratory and is confused after observing the ion concentration gradient in the image below. Initially (Time 1) there was a very strong concentration gradient across the membrane and your friend expected that ions would move until the concentrations were equal across the membrane. For a short time there was movement of ions but this soon stopped and there is no further change in the situation no matter how long you wait (see Time 2). Time 1 You friend is confused because there is still a strong concentration gradient and there are open ion channels available. So why don't the concentrations equalise? After thinking about it you realise that there must be some information that is incorrect or missing from the diagram above. Select the image below that explains why the ion concentrations remain unequal across the membrane Time 2 Select the correct image by clicking on it (you can only select one…

what would the membrane potential be if the membrane became 10X more permeable to both sodium and chloride

The equilibrium potential for a given ion (Eion) is a theoretical value. For a given concentration gradient of an ion, the equilibrium potential is the charge inside the cell required to hold an ion at that concentration. That is, it is the charge required to perfectly oppose the drive of the ion to move down its concentration gradient. So, if the concentration of Nat is higher outside the cell than inside, its equilibrium potential (ENa) must be I and if we add more sodium to the extracellular fluid, then ENa will II.