Question

The sodium/calcium exchanger (NCX) transports sodium into and calcium out of cardiac muscle cells. Describe why this transporter is classified as secondary active transport.

a) It directly utilizes ATP for energy
b) It requires a concentration gradient
c) It relies on the movement of sodium
d) It involves the transport of multiple ions

Answer 1

The sodium/calcium exchanger (NCX) is classified as secondary active transport because it relies on the movement of sodium to transport calcium.

Step-by-step explanation:

Secondary active transport brings sodium ions into the cell by utilizing the concentration gradient established by primary active transport. As the sodium ion concentration increases outside the cell, sodium ions are pulled through the membrane, creating an electrochemical gradient. This movement of sodium ions transports other substances, such as calcium, that can attach to the transport protein through the membrane. Therefore, the sodium/calcium exchanger (NCX) is classified as secondary active transport because it relies on the movement of sodium to transport calcium.