14 Can Science Explain Life? 



Ornithine NH 2 CO— OH 



\ / 



CH 2 — CH> — CHo — CH 



NH 2 



Lysine NH 2 CO— OH 



\ / 



CHo — CH> — CHo — CH 2 — CH 



NH, 



Hydroxy- and Thio-amino acids: 



Serine CO— OH 



HOCH 2 — CH 



NH 2 

 Hydroxyglutamie acid H CO — OH 



CH 2 — CH— CH 



/ \ 



HO— OC NH 2 



Cysteine CO— OH 



HS— CH— CH 



\ 



NH 2 



Cystine NH 2 CO— OH 



CH— CH 2 — S— S— CH 2 — CH 



/ \ 



HO— OC NH 2 



Glutathione (y-glutamylcysteylglycine) 



CO— OH 

 / 



HO— OC CH 2 CO NH 



\ S/ ^CH— CH 2 — SH 



CH— CH 2 — CH 2 NH CO 



NH 2 



