BIOCHEMISTRY - Main Regulators and Biological Fluids of the Human Body - 2016

2. HORMONES

2.9. The Role of Calcium Ions as Mediators in Hormone-Induced Changes in Enzyme Activity

Ionized calcium serves as an intracellular mediator for the action of A number of Hormones that regulate The activity of many Enzymes, Cell membrane excitability, Blood clotting reactions, and other processes.

The intracellular concentration of Calcium Ions (Ca2+) is much lower than the extracellular concentration. Ca2+ ions enter The Cell from the external environment via two calcium pumps located in the membrane. The pumping out of Ca2+ ions is carried out by Ca2+-ATPase in exchange for extracellular Na+ ions.

Hormones bind to Membrane Receptors, which alters the activity of Ca2+-ATPase. Calcium ions enter the cell and interact with cytoplasmic Proteins that act as regulators, such as calmodulin. As a result, a "Ca2+-calmodulin" complex is formed, which is capable of regulating the activity of various enzymes. Ultimately, cellular Functions are altered.



Last update: 06/08/2026

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