What is the reason for negative voltage of a neuron during Resting Potential?

Correct option is B

During resting potential (approximately -70mV), the neuron's interior is negatively charged relative to the exterior. This occurs because organic anions (A⁻) are trapped inside the cell (being too large to cross the membrane), and the sodium-potassium pump maintains higher K⁺ concentration inside and higher Na⁺ concentration outside. Although both Na⁺ and K⁺ are positive ions, the impermeant organic anions create a net negative charge inside. The statement means that the outside (with Na⁺ and Cl⁻) has less negative charge (i.e., is more positive) compared to the inside (with K⁺ and A⁻), which has more negative charge—establishing the resting potential's polarity.

Information Booster:
● Resting Potential: Electrical potential difference across the neuronal membrane at rest, typically -70mV (inside negative relative to outside)
● Sodium-Potassium Pump (Na⁺-K⁺ ATPase): Active transport mechanism that pumps 3 Na⁺ out and 2 K⁺ in, contributing to charge separation and concentration gradients
● Organic Anions (A⁻): Large negatively charged proteins and molecules trapped inside the cell; major contributors to intracellular negativity
● Ionic Distribution: Resting state maintains high K⁺ inside (~140mM), high Na⁺ outside (~145mM), high Cl⁻ outside (~110mM), and high A⁻ inside
● Equilibrium Potentials: K⁺ equilibrium ≈ -90mV; Na⁺ equilibrium ≈ +60mV; resting potential represents weighted average closer to K⁺ due to selective permeability
● Goldman-Hodgkin-Katz Equation: Calculates membrane potential based on relative permeabilities and concentrations of all ions