ðə sˈoːɹs ʌvðə kˈɑːmpaʊnd ɪn bˌaɪəlˈɑːdʒɪkəl sˈɪstəmz ɪz ðə ɹɪˈækʃən bᵻtwˌiːn sˈɪŋɡlɪt ˈɑːksɪdʒən ænd wˈɔːɾɚ wˌɪtʃ pɹəsˈiːdz ɪn ˈiːðɚ dᵻɹˈɛkʃən, ʌv kˈoːɹs, ɐkˈoːɹdɪŋ tə kˌɑːnsəntɹˈeɪʃənz, wɪððə sˈɪŋɡlɪt ˈɑːksɪdʒən bˌiːɪŋ pɹədˈuːst baɪ ɪmjˈuːn sˈɛlz.
The source of the compound in biological systems is the reaction between singlet oxygen and water (which proceeds in either direction, of course, according to concentrations), with the singlet oxygen being produced by immune cells.