During calcium signaling calcium ions act as second messengers in signal transduction. The concentration of Ca++ in the cytoplasm is in the range of 10 - 100 nM. Certain proteins of the cytoplasm and organelles acting as buffers by binding Ca-ions.
Second messengers are intracellular signals. Specific signals can trigger sudden increase in the cytoplasm Ca++ level up to 500 - 1 000 nM by opening channels in the plasma membrane.
The biochemical effects of Ca++ are regulating enzyme activity, ion pumps, and components of the cytoskeleton.
Source
- Koolman, Roehm. Color Atlas of Biochemistry. Thieme, 2005 ISBN 1-58890-242-1