Use the scenario and figure below to answer questions 19 21

Use the scenario and figure below to answer questions 19- 21 Below is a depiction of a portion of the cell membrane that is positively charged on the intracellular side and negatively charged on the extracellular side. Further, in this cell the concentration of ion X^+ in the intracellular space is high and in the extracellular space is low. Does an electrical or chemical gradient exist for X^+? If so, what direction is the gradient?

Solution

Please find the answer:

Part 19) Since the concentration of X and Y are different on different sides of plasma membrane and both molecules are electrically charged, there would be a chemical and electric gradient across the plasma membrane. Since movement molecules takes place from a region of higher concentration to a region of lower concentration, the chemical gradient across the membrane with respect to X and Y would be from inside to outside.

Similarly, it can be seen that intracellular region is electropositive and extracellular is electronegative. The plasma membrane is itself negatively charged in nature. This will also generate an electric gradient across the plasma membrane. The outer part would be electro-negative and inside would be electro-positive.

Importance: With this reference of ions (concentration and charge), a slight movement of ions from either side would disturb the electro-chemical gradient and will excite the plama membrane. This is a mode of transfer of inforomation across the plamsa membrane in many types of cells such as skeletal muscle cells, cardiac cells, neurons etc.