A cotransporter is something that moves two substances across a membrane, one passively and the other actively. The \(\mathrm{Na}^{+} \mathrm{K}^{+}\) ATPase transports sodium and potassium ions across the plasma membrane against their concentration gradients. This pump is not considered a cotransporter because (A) ATP is produced through this transporter (B) both ions are moved via active transport (C) both ions are moved via passive transport (D) ATP hydrolysis does not occur during transport

A cotransporter is a protein that moves two substances across a membrane simultaneously. One substance moves passively, following its concentration gradient, while the other substance moves actively, against its concentration gradient. Passive transport does not require energy as molecules move from a higher concentration to a lower concentration, while active transport requires energy, usually in the form of ATP, as molecules move against their concentration gradient.

The Na+/K+ ATPase pump transports sodium and potassium ions across the plasma membrane against their concentration gradients. Sodium ions (Na+) are moved out of the cell and potassium ions (K+) are moved into the cell. Both ions are transported against their concentration gradients, which means that energy is required for this process. This energy comes from the hydrolysis of ATP.

(A) ATP is produced through this transporter: This is incorrect because ATP is actually consumed, not produced, during the transport process. (B) Both ions are moved via active transport: This statement is correct. As mentioned earlier, both Na+ and K+ are moved against their concentration gradients, which requires energy in the form of ATP. So, both ions are moved via active transport. (C) Both ions are moved via passive transport: This is incorrect because both ions are moved against their concentration gradients, requiring energy in the form of ATP, which indicates that it's an active transport process. (D) ATP hydrolysis does not occur during transport: This is incorrect because ATP hydrolysis is the source of energy required for the active transport of the Na+ and K+ ions.

From the given options, we can see that (B) both ions are moved via active transport is the correct answer. The Na+/K+ ATPase is not considered a cotransporter because it moves both ions against their concentration gradient through active transport, unlike a cotransporter that moves one substance passively and the other actively.