Contents [hide] 
1 Production
2 Acid-base properties and structures
3 Metabolism
3.1 Biosynthesis
3.2 Degradation
4 Physiological function
4.1 As a biosynthetic intermediate
4.2 As a neurotransmitter
5 Uses
5.1 Animal and human foods
5.2 Cosmetics and miscellaneous applications
5.3 Chemical feedstock
5.4 Research and Development
5.5 Anti-aging properties
6 Presence in space
7 See also
8 References
9 Further reading
10 External links