In certain cells, a transport protein moves one calcium ion out of the cell against its concentration gradient while allowing the movement of three sodium ions into the cell down sodium's electrochemical gradient. Which of the following CORRECTLY describes this cotransport of calcium and sodium?a. primary active transport by an antiporterb. primary active transport by a symporterc. secendory active transport by a symporter
d. secendory active transport by an antiporter

The correct answer is option d. "secondary active transport by an antiporter".

Explanation:

The cotransport of calcium and sodium at which one calcium ion moves out of the cell and three sodium ions move into the cell is known as secondary active transport by an antiporter. It is secondary because it uses a form of energy different from ATP, is an active transport because the calcium ion moves against its gradient, and its done by an antiporter which is an integral membrane protein that function as a cotransporter.

d. secondary active transport by an antiporter

Explanation:

Secondary active transport is a type of transport which uses gradient produces by another protien using ATP. It has two methods :

1) Symport : Solutes flow in same direction of the ion gradient (cotransport) as in the case of sodium glucose transporter

2) Antiport : Ions flow in one direction to generate the energy to transport the solutes in other direction .

Na/Ca exchanger is basically removing Calcium ions from the cell by inward flow of Na ions . Hence it is an example of secondary active transport by an antiporter

the correct answer is:

a population changes in response to a change in the environment.