Final answer:
When chloride channels open in a cell with a membrane potential of -55 mV, it will lead to hyperpolarization as chloride ions move into the cell to bring the membrane potential closer to the equilibrium potential of -63 mV.
Step-by-step explanation:
If a cell has a membrane potential of -55 mV and chloride channels open, what will happen to the membrane potential? Assuming that the equilibrium potential for chloride (Cl-) is -63 mV, the action of Cl- ions moving across the membrane will influence the membrane potential.
Since the membrane potential is less negative than the equilibrium potential for Cl-, opening chloride channels would result in Cl- ions moving into the cell to try and bring the membrane potential closer to the equilibrium potential.
When the Cl- channels open, there would be an influx of Cl- ions due to the chemical gradient, and because Cl- is a negatively charged ion, its movement into the cell will make the membrane potential more negative, hence moving it toward the equilibrium potential of -63 mV.
This process is known as hyperpolarization, meaning the membrane potential will become more negative than the resting membrane potential.