In kidney cells charged ions like sodium and chloride are reabsorbed from the urine against a concentration gradient. Which mode of cellular transport is employed here?

The reabsorption of charged ions like sodium and chloride from urine against a concentration gradient in kidney cells primarily employs active transport. This process requires energy, often in the form of ATP, to move ions from an area of lower concentration in the urine to an area of higher concentration in the bloodstream. Specific transport proteins, such as pumps and co-transporters, facilitate this movement across the cell membrane.