Resting potential describes the cell when the outside is positively charged and the inside is negatively charged.

• A. Outside is positively charged relative to inside
• B. Outside is negatively charged relative to inside
• C. There is no charge difference
• D. Inside is positively charged relative to outside

Answer: (A)

Resting membrane potential is about the charge separation across the cell membrane. The distribution of ions is such that the inside becomes negatively charged relative to the outside, making the outside effectively more positive. This difference is maintained by the Na+/K+ pump and leak ion channels, which together keep the inside negative and the outside positive. Describing the outside as positively charged relative to the inside captures this resting state. If the outside were negative relative to the inside, or if there were no charge difference, the cell wouldn’t be at its typical resting potential. Inside positive relative to outside would imply the opposite polarity.