Question

In mechanism of hormone action, which of the following is not a second messenger?

• A. Cyclic AMP
• B. $I{P}_3$
• C. $C{a}^{++}$
• D. $M{g}^{++}$

Answer 1

The correct option is D $M{g}^{++}$

Hormones which are made up of proteins or steroids are chemical messengers that enable communication between cells. Hormones are secreted by the glands of the endocrine system and help in maintaining homeostasis and regulates metabolism, reproduction, and development. The protein hormones that are released bind to a specific receptor on target cells and trigger intra-cellular signals. Since the signal transduction begins when a hormone is released into the bloodstream, this hormone is the called the first messenger. The hormone further binds to specific cell membrane receptors. The binding of the hormone to the receptor sends across conformational changes that produce a response in the cytosolic side of the cell. These responses bring about a change of concentration of small molecules called the second messengers such as cyclic AMP, cyclic GMP, Ca2+, inositol 1,4,5 triphosphate (IP3) and diacylglycerol, DAG which ultimately brings about upregulation or downregulation of certain genes or molecules. Magnesium ions do not play a role as secondary messengers.