Calcium pumps are specialized proteins found in cell membranes that help regulate the levels of calcium ions within cells. They work by actively transporting calcium ions out of the cell or into the endoplasmic reticulum, which is essential for various cellular functions, including muscle contraction and neurotransmitter release. These pumps use energy from ATP (adenosine triphosphate) to move calcium ions against their concentration gradient, ensuring that the cell maintains a low concentration of calcium ions inside. This process is crucial for maintaining cellular health and function, as imbalances in calcium levels can lead to various diseases.