Practice question

Observing stochastic opening and closing of an individual channel requires isolating its picoampere current from background of thousands of other channels. Patch-clamp achieves this by sealing a glass pipette against membrane with gigaohm resistance, confining one channel within patch. Cell-attached or excised patch modes reveal unitary amplitude, conductance states, burst behavior and pharmacological block of sodium, potassium, calcium and acetylcholine receptor channels. Simultaneous multi-channel macroscopic currents represent average activity, voltage-gated pumps transport actively without discrete steps, so only single-channel visualization matches this capability.