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. Ion channels and carrier proteins.

E. Cotransport proteins, ion channels, and carrier proteins.

The correct answer is option A, that is, cotransport proteins.

Explanation:

The variable that possesses the tendency to mediate energy based on chemical potential is termed as an electrochemical gradient. The electrochemical gradient is differentiated into two parts, that is, electrical gradient and chemical gradient. Both these forms of gradient take place over the surface of a membrane.  

The movement of the majority of the ions takes place by the phenomenon of electrochemical gradients, of which some are found on the surface of the membrane and function as electrogenic pumps. While the gradients of some of the ions are mostly accounted for by the co-transport proteins, as these proteins take part in the movement of ions or molecules through a plasma membrane that involves concentration gradient based on the kind of molecules and movement.  

the generally accepted parts of modern cell theory include: all known living things are made up of one or more cells. all living cells arise from pre-existing cells by division. the cell is the fundamental unit of structure and function in all living organisms.