Question

Which among the following belongs to the class of second messengers?

• A. Hormones, neurotransmitters
• B. Pharmacological agonists
• C. cAMP, cGMP, DNA binding
• D. Ions, protein kinases

Hint:

• First messengers: Extracellular signals (e.g., hormones, neurotransmitters).
• Second messengers: Intracellular signaling molecules that relay and amplify the signal from a receptor.
• Key second messengers: cAMP, cGMP, Ca\(^{2+}\), IP\(_3\), DAG.
• Protein kinases are enzymes involved in signal transduction, often activated by second messengers, but are not second messengers themselves.

Answer 1

The Correct Option is C

The concept of second messengers is fundamental in biotechnology and cellular signaling. Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules, such as hormones and neurotransmitters. The primary role of these second messengers is to transmit and amplify the signal from the first messenger (the extracellular signaling molecule).
Among the options provided:

Option	Explanation
Hormones, neurotransmitters	These are first messengers and act at the cell surface, not inside the cell.
Pharmacological agonists	These mimic the action of neurotransmitters or hormones but are also first messengers.
cAMP, cGMP, DNA binding	cAMP (cyclic adenosine monophosphate) and cGMP (cyclic guanosine monophosphate) are well-known second messengers within cells. DNA binding does not directly relate to the concept of second messengers.
Ions, protein kinases	While some ions like calcium can serve as second messengers, protein kinases typically act as effectors in the signaling pathway, not primary second messengers.

Thus, the correct answer is "cAMP, cGMP, DNA binding", acknowledging that cAMP and cGMP are classical examples of second messengers that propagate intracellular signaling.