Multiple Choice
Cells that communicate with each other by direct contact typically use which type of cell junction?
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5. Cell Components
Cell Junctions
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Which of the following will cause the plasma membrane to hyperpolarize when at its resting membrane potential (RMP)?
A
Opening of potassium (K^+) channels
B
Opening of sodium (Na^+) channels
C
Closing of chloride (Cl^-) channels
D
Opening of calcium (Ca^{2+}) channels
Verified step by step guidance1
Understand the concept of resting membrane potential (RMP): The RMP is the electrical potential difference across the plasma membrane of a cell at rest, typically around -70 mV in neurons. It is maintained by the distribution of ions such as potassium (K⁺), sodium (Na⁺), chloride (Cl⁻), and calcium (Ca²⁺) across the membrane.
Recall the role of potassium (K⁺) in RMP: Potassium ions are more concentrated inside the cell than outside. At rest, potassium channels allow K⁺ to leak out of the cell, making the inside of the cell more negative relative to the outside. This contributes significantly to the RMP.
Define hyperpolarization: Hyperpolarization occurs when the membrane potential becomes more negative than the RMP. This can happen if positive ions (like K⁺) leave the cell or if negative ions (like Cl⁻) enter the cell.
Analyze the effect of opening potassium (K⁺) channels: If K⁺ channels open, more K⁺ ions will flow out of the cell, increasing the negative charge inside the cell. This will cause hyperpolarization.
Compare the effects of other ion channels: Opening sodium (Na⁺) or calcium (Ca²⁺) channels would allow positive ions to enter the cell, making the inside less negative (depolarization). Closing chloride (Cl⁻) channels would reduce the entry of negative ions, also leading to depolarization. Therefore, only the opening of potassium (K⁺) channels will cause hyperpolarization.
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