Answer: A protein acts as a pump and moves calcium ions from an area of low concentration to an area of high concentration.
There are primarily two types of the transport system which occurs through the cell membrane. These are Active transport and passive transport. Active transport facilitates the movement of substances from a medium of lower concentration to a medium of higher concentration. Energy is required for the movement of substances against the concentration gradient. This is accomplished by ATP ( adenosine triphosphate) powered pumps or some other source like an electrochemical gradient.
On the other hand, in passive transport, substances move from a medium of higher concentration to lower concentration.
As \(Ca^{2+}\) ions are moving from low to higher concentration via protein pump, therefore, it accurately describes the movement through active transport.
