Final answer:
Calcium ions act as messengers in cells, activating or inactivating cellular components. They can activate enzymes that break down various molecules. Calcium ions are stored or accessed when signaling occurs, and their response varies depending on the cell type.
Step-by-step explanation:
Calcium ions act as intracellular messengers, activating or inactivating various cellular components. For example, they can activate proteases that break down proteins, nucleases that break down RNA and DNA, and phospholipases that break down phospholipids. Calcium ions are stored in cytoplasmic vesicles or accessed from outside the cell, and when signaling occurs, ligand-gated calcium ion channels allow them to flow into the cytoplasm. The response to the increase in calcium ions varies depending on the cell type.