Question

In heart cells, which one serves as a second messenger, speeding up muscle cell contraction in response to adrenaline?
(a)cAMP
(b)cGMP
(c)GTP
(d)ATP

Answer 1

This is a very important second messenger for hormone adrenaline, glucagon, and luteinizing hormone. This is a derivative of adenosine triphosphate and used for intracellular signal transduction.

Complete answer:
In the heart cells, cAMP is the second messenger, that is speeding up the contraction of muscle fiber in response to adrenaline. Second messengers are those molecules that relay the signal from the receptors that are present on the cell surface to the target molecules present in the cytosol or nucleus. Other than this relay job the second messengers also serve to greatly amplify the strength of the signal.

Additional Information: -The hormone adrenaline, glucagon, and luteinizing hormone achieve their effects through cyclic AMP as a second messenger that activates protein kinase which in turn activates phosphorylase kinase which forms more ATP.
-By the action of enzyme adenylyl cyclase, cyclic AMP is synthesized from ATP. It activates the binding of the hormone to its receptor.
- More ATP results in more cyclic AMP that leads to speed up of muscle contraction.
-cGMP is synthesized from the nucleotides GTP by the action of enzyme guanylyl cyclase. It serves as a second messenger for atrial natriuretic peptide (ANP) and nitric oxide (NO).
-GTP is an energy-rich nucleotide composed of guanine, ribose, and 3 phosphate groups also called guanosine triphosphate. It is necessary for the formation of a peptide bond during protein synthesis.
-ATP is also called adenosine triphosphate. It is an organic compound that provides energy to carry out many processes in living cells for example muscle contraction, nerve impulse propagation, chemical synthesis, etc.
So, the correct answer is,'cAMP'.

Note: -cyclic AMP is a second messenger that activates protein kinase which in turn activates phosphorylase kinase which forms more ATP
-cyclic AMP is synthesized from ATP.
-More ATP results in more cyclic AMP that leads to speed up of muscle contraction.