Final answer:
Serotonin, also known as 5-hydroxytryptamine, is a neurotransmitter and hormone synthesized from tryptophan. It regulates many physiological processes and acts as a precursor to melatonin, affecting sleep cycles and circadian rhythms.
Step-by-step explanation:
The substance synthesized from the amino acid tryptophan found in almost all organisms and acting as both a neurotransmitter and a hormone is serotonin, also known as 5-hydroxytryptamine (5-HT). Serotonin is crucial for the serotonergic system, having specific receptors for its function. It is produced in the presynaptic cell and, after being released and fulfilling its role, it is transported back into this cell for repackaging. Moreover, serotonin serves as a precursor for the production of melatonin in the pineal gland.
Melatonin regulates sleep cycles by controlling circadian rhythms and is an example of an amino acid-derived hormone. The conversion process of tryptophan to serotonin involves hydroxylation to 5-hydroxytryptophan and then decarboxylation. The availability of tryptophan directly affects serotonin synthesis, which is essential for many physiological processes including mood regulation, digestion, and blood clotting.