At physiological pH, typically around 7, free amino acids exist in a charged form, where the acidic carboxyl group (-COOH) loses a proton (-COO−) and the basic amine group (-NH2) gains a proton (-NH).
æt fˌɪzɪəlˈɑːdʒɪkəl pˈiː ˈeɪtʃ, tˈɪpɪkli ɚɹˈaʊnd sˈɛvən, fɹˈiː ɐmˈiːnoʊ ˈæsɪdz ɛɡzˈɪst ɪn ɐ tʃˈɑːɹdʒd fˈɔːɹm, wˌɛɹ ðɪ ɐsˈɪdɪk kˈɑːɹbəksˌɪl ɡɹˈuːpkˈuː lˈuːzᵻz ɐ pɹˈoʊtɑːnsˌiːˌoʊˈoʊ mˈaɪnəs ænd ðə bˈeɪsɪk ˈæmaɪn ɡɹˈuːpˌɛnˈeɪtʃ tˈuː ɡˈeɪnz ɐ pɹˈoʊtɑːnˌɛnˈeɪtʃ.