Question

Choose the correct statement from the alternatives given, Second messengers include
A. Steroid hormones
B. Cyclic AMP
C. Protein hormones
D. Both A and B

Answer 1

Hint: A second messenger, a molecule within cells that transmits signals from a receptor to a target. To differentiate them from hormones and other molecules that act outside the cell as "first messengers" in the transmission of biological information, the term second messenger was coined upon the discovery of these substances.

Complete Answer:
- Many second messenger molecules are small and thus easily disperse through the cytoplasm, allowing data to travel rapidly across the cell.
- Second messengers may serve to incorporate information as elements of signalling pathways when multiple independent upstream inputs influence the synthesis and degradation rates of the second messenger. Furthermore, second messengers may have several downstream goals, extending the signal transmission range.
- Cyclic nucleotides (e.g., cyclic adenosine monophosphate or cAMP and cyclic guanosine monophosphate or cGMP), ions (e.g., $Ca^{2+}$), molecules derived from phospholipids (e.g., inositol triphosphate), and also gas, nitric oxide (NO) have been described by a large number of second messenger molecules.
- Adenylyl cyclase enzymes, downstream of heterotrimeric G-proteins (guanine nucleotide binding proteins) and receptors, are synthesised by the cyclic nucleotide cAMP. For example, G-protein activation stimulates the synthesis of cAMP by adenylyl cyclase when epinephrine binds to beta-adrenergic receptors in the cell membranes.
- Intracellular receptor interacting hormones (e.g., steroid hormones, iodothyronines, etc.) mainly control gene expressions or chromosome function by interacting with the genome complex of hormone receptors.

The correct answer is option (B) Cyclic AMP.

Note: By inhibiting the enzyme phosphodiesterase, which degrades cAMP, caffeine also improves the action of cAMP; increasing cAMP activity leads to caffeine 's overall stimulatory action. As a gas, in being able to diffuse through cell membranes, nitric oxide (NO) is separate from second messengers, allowing signal information to pass through neighbouring cells.