What are the functions of amino acids?

Amino acids have several important functions in the body: 

• They are critical for the health of the human body by maintaining normal cellular structure, the health of vital organs and muscle structure, regulating hormone production, and ensuring the healthy functioning of the nervous system. 
• 20 amino acids are particularly important for life as they contain peptides and proteins that are the building blocks for all living beings. 
• Various tissues use amino acids to synthesize proteins as well as nitrogen-containing compounds such as creatinine, heme, purines, and epinephrine. Some amino acids are used to produce energy through oxidation.  
• Because amino acids are amphoteric in nature, they are used as buffers in solutions where they resist pH changes by donating H+ ions as pH increases and accepting H+ as pH decreases.