The sodium-potassium antiporter normally transports sodium and potassium across the membrane. This antiporter sets up concentration gradients across the membrane. The typical concentrations are
a. [sodium] higher inside than outside and [potassium] lower inside than outside.
b. [sodium] lower inside than outside and [potassium] higher inside than outside.
c. both [sodium] and [potassium] higher inside than outside.
d. [sodium] and [potassium] equal on either side of the membrane.