They can be viewed as molecular trees upon which can be hung the more active/reactive functional groups of biological molecules.
ðeɪ kæn biː vjˈuːd æz məlˈɛkjʊlɚ tɹˈiːz əpˌɑːn wˌɪtʃ kæn biː hˈʌŋ ðə mˈoːɹ ˈæktɪv slˈæʃ ɹɪˈæktɪv fˈʌŋkʃənəl ɡɹˈuːps ʌv bˌaɪəlˈɑːdʒɪkəl mˈɑːlɪkjˌuːlz.