Calcium is an essential signaling molecule required for various cellular functions. Calcium pumps and ion channels on cell and organellar membranes, such as those on the endoplasmic reticulum (ER), regulate calcium concentrations inside the cell. They remain closed, keeping the cytosolic calcium levels low at a resting state.
Various transmembrane receptors, such as G protein-coupled receptors (GPCRs), elicit a response to extracellular signals by increasing cytosolic calcium. Activated GPCRs...

Calcium and phosphate are essential electrolytes in the human body, with calcium being the most abundant mineral. Around 99% of the body's calcium is stored in the skeleton and teeth, forming a crystal lattice of mineral salts in combination with phosphates. Calcium plays crucial roles in various bodily functions such as blood clotting, neurotransmitter release, muscle tone maintenance, and nervous and muscle tissue excitability.
The calcium concentration in blood plasma is primarily regulated...

The two pairs of parathyroid glands embedded within the posterior surface of the thyroid gland are restricted by a dense capsule around them. These glands comprise two distinct cell populations—parathyroid oxyphil and parathyroid principal cells- pivotal in calcium homeostasis.
Oxyphil cells, whose functions remain elusive, emerge during late puberty, adding a layer of complexity to the parathyroid gland's intricacies. In contrast, principal parathyroid cells undertake a vital role by producing...

Calcitonin, a vital polypeptide hormone, regulates calcium levels within body fluids. It is released by the parafollicular cells, also known as C cells, situated in the follicular epithelium of the thyroid gland. Calcitonin responds to fluctuations in blood calcium levels and the influence of gastrointestinal hormones like gastrin and cholecystokinin.
The exact mechanisms by which calcitonin operates in calcium homeostasis remain elusive, but its significance is evident in several vital...

Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...