Assume that a yeast cell has a cytosollc K^+ concentration of 100 mM and is grow
ID: 166383 • Letter: A
Question
Assume that a yeast cell has a cytosollc K^+ concentration of 100 mM and is growing at 25 degree C m a medium with a concentration of 10 mM K^+. The membrane potential If -100 mV, Inside negative with respect to the outside. There are a variety of K^+ channels in the plasma membrane of this yeast, some of which are ligand gated. Is K^+ "at a higher" free energy Inside or outside of the cell or is it at equilibrium? ii. In which direction would K^+ move in the presence of ligand (when the K^+ channels open)? Refer to your calculations to explain why you have chosen a particular direction of movement. iii. How will this K^+ flux initially impact the membrane potential of the cell? iv. Would this yeast cell likely have an active K^+ pump? If so, in which direction would this pump be actively transporting K^+? v. What is the equilibrium or Nernst potential for K^+ across this membrane? Please define equilibrium potential and show (derive) how the equation for equilibrium (Nernst) potential comes from the equation for Delta G_inside-outside.Explanation / Answer
1. Is K+ at a free energy inside or outside the cell or is it at equilibrium?
Since the cytosolic concentration i.e. 100mM is more than medium concentration i.e. 10mM; K+ is having free energy inside only.
2. To which direction would K+ move in the presence of ligand (when the K+ channels open)? Refer to your calculations to explain why you have chosen a particular direction of movement?
Since the cytosolic concentration i.e. 100mM is more than medium concentration i.e. 10mM; K+ will move outside the cell when K+ channels open.
3. How this K+ flux initially impact the membrane potential the cell?
Since the K+ has been moved out of the cell, negativity of the membrane potential increases i.e. membrane potential will move towards the direction of -101 mV, -102mV …
4. Would this yeast cell likely have an active K+ pump? If SO, in which direction would this be actively transporting K+?
Yes, this yeast will likely to have an active K+ pump. If active K+ pump is there, then that pump will enable the movement of K+ from outside to inside of the cell.
Note: As per the guidelines we can answer only 4 subparts of a single question. So I did not answer the fifth subpart. Hope you can understand.