Resting membrane potential arises primarily from ion concentration gradients and selective membrane permeability, with the Na+/K+ pump maintaining these gradients. The correct answer is B, C, and D only.

Option Analysis

• A. Active transport: Partially involved but not directly “conducted by” it. The Na+/K+ ATPase pump uses active transport to establish ion gradients (high K+ inside, high Na+ outside), but the potential itself results from passive ion movements down these gradients.

• B. Selective permeability of phospholipid bilayer: True. The bilayer is more permeable to K+ than Na+ due to leak channels, allowing K+ efflux that drives the negative potential (~-70 mV).

• C. Passive diffusion across lipid bilayer: True. K+ and other ions diffuse passively through channels (not directly across the bilayer for charged ions, but via lipid-soluble paths and channels), contributing to the equilibrium.

• D. Differential distribution of ions across membrane: True. Unequal ion concentrations (e.g., [K+] high inside, [Na+] high outside) create electrochemical gradients essential for the potential, per the Goldman-Hodgkin-Katz equation.

Introduction to Resting Membrane Potential

Resting membrane potential conducted by ion gradients and permeability is fundamental in neurons and excitable cells. This ~ -70 mV charge difference (inside negative) enables action potentials. It relies on K+, Na+, and Cl- distributions with membrane properties.

Role of Selective Permeability

The phospholipid bilayer’s selective permeability favors K+ leak channels over Na+, allowing K+ efflux. This permeability difference dominates the potential via Nernst equilibrium for K+ (~ -90 mV), balanced slightly by Na+ influx.

Passive Diffusion Mechanism

Passive diffusion across lipid bilayer (via channels) lets ions follow gradients: K+ out, contributing negativity; minor Na+ in. No energy required, unlike pumps; this diffusion establishes steady-state potential.

Ion Distribution and Active Maintenance

Differential distribution of ions (high intracellular K+, extracellular Na+) creates driving forces. Na+/K+ pump (active transport) sustains gradients indirectly, but potential is “conducted” by passive factors.

Exam Insights for Biology Students

In questions like “Resting membrane potential is conducted by,” B, C, D hold as core mechanisms; A supports but isn’t primary. Key for GATE Life Sciences, NEET prep on electrophysiology.