Origin of membrane potentials

Which molecules can cross the membrane via simple diffusion

Small, non-polar, lipid-soluble molecules (O2, CO2, steroid hormones)

How does active transport differ from passive transport

Active transport requires ATP while passive transport does not

What is a concentration gradient

A difference in soluble concentration across a membrane that drives diffusion

What is meant by electrical gradient

The difference in electrical charge across a membrane that influences ion movement

What is the equilibrium potential for an ion

The membrane potential at which the is no near movement of ions across the membrane

Which equation is used to calculate equilibrium potential

The Nernst equation

Why do different ions have different equilibrium potentials

Because equilibrium potential depends on the ratio of extracellular to intracellular concentrations for each ion