Question

Which one of the following is not a second messenger in hormone action?
A) Sodium
B) cAMP
C) cGMP
D) All of the above

Answer 1

Hint:Hormones are the chemical messengers, that are directly secreted in the blood by the endocrine glands (ductless glands). Blood carries these hormones to the particular organ or tissue of the body to exert their functions.

Complete answer:
Second messengers:
>Second messengers are first discovered by Earl Wilbur Sutherland, Jr. for which he won a Nobel prize in Physiology and medicine.
>Second messengers are the intracellular (within the cell) signaling molecules.
>These molecules are released in response to the exposure of extracellular (outside the cell) signaling molecules i.e. first messenger.
>Second messengers trigger physiological changes at the cellular level such as the differentiation, migration, survival, proliferation, etc.
>Example of second messengers are cAMP (cyclic adenosine mono-phosphate), cGMP (cyclic guanosine mono-phosphate), inositol triphosphate, calcium, diacylglycerol, etc.
Types of second messengers:
There are three types of second messengers-
>Hydrophobic messengers – These are the water insoluble molecules. These molecules are membrane associated and diffuse from the plasma membrane into the intermembrane space. Example – diacylglycerol
>Hydrophilic messengers – These are the water soluble molecules. They are located within the cytosol. Example – cAMP, cGMP, etc.
>Gases – These are the gaseous molecules which can diffuse both through cytosol and across cellular membranes. Example – nitric oxide, carbon monoxide, etc.
Therefore, it has been clear from the above discussion that Sodium is not a second messenger in hormone action.

Hence, the option A is the correct answer.

Note:These second messengers can be synthesized and broken down again in specific reactions with the help of some enzymes or ion channels. Some of the second messengers get stored in special organelles and released when needed.