In Most Cells, There Are Electrochemical Gradients of Many Ions

Multiple Choice

In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by

A) cotransport proteins.
B) ion channels.
C) carrier proteins.
D) passive diffusion across the plasma membrane.
E) cellular metabolic reactions that create or destroy ions.