Final answer:
Tryptophan exhibits a more extensive loss of vibrational energy post excitation compared to tyrosine and plays critical metabolic roles, leading to the production of serotonin and melatonin, and contributing to niacin synthesis, which makes it 'stronger' in a biochemical context than phenylalanine.
Step-by-step explanation:
When considering the properties and strength of the amino acids phenylalanine and tryptophan, it is essential to define in what context 'stronger' is being evaluated. In terms of fluorescent properties, tryptophan fluorescence is lower in energy and has a longer wavelength compared to tyrosine, as suggested by energy diagrams. This indicates that tryptophan experiences more significant energy loss to vibrations post-excitation.
In terms of physiological roles and metabolic pathways, tryptophan is an essential, glucogenic and ketogenic amino acid with complex metabolism. It leads to the production of serotonin, a critical neurotransmitter, through the conversion of tryptophan to 5-hydroxytryptamine. Serotonin is further implicated in the synthesis of melatonin, another significant hormone involved in regulating circadian rhythms. A small amount of tryptophan converts to niacin, which can have a sparing effect on niacin requirement, emphasizing the significance of a tryptophan-rich diet.
The metabolism of tryptophan in malignant conditions such as carcinoids leads to a substantial increase in serotonin production as compared to regular physiological levels, resulting in several symptoms such as pellagra and negative nitrogen balance. Therefore, based on its diverse roles in biological systems, including its involvement in producing serotonin and melatonin as well as its contribution to niacin synthesis, tryptophan can be considered 'stronger' in a biochemical context than phenylalanine.