. Biochemistry of plants and animals, an introduction. Biochemistry. PROTEINS 121 although others may be found. In addition, glucose, galactose, and other sugars occur in special nucleotides of metabolic importance but have not been isolated from nucleic acids. The bases belong to two series, derivatives of pyrimidinc and purine. These are: N-^^^^ â N^ -N ,^ -NH liyriiiiidine punnp The four pvrimidincs most abiuulant in nucleic acids arc: H.,N ,1^ N. ',0 H '.O NH .NH CHg H ,N. .-^ O Nâ â :y NH cytosine uracil thymine H.,Nr^^-V^" 5 - methylcytosine One other, hydroxymethylcytosine, has
. Biochemistry of plants and animals, an introduction. Biochemistry. PROTEINS 121 although others may be found. In addition, glucose, galactose, and other sugars occur in special nucleotides of metabolic importance but have not been isolated from nucleic acids. The bases belong to two series, derivatives of pyrimidinc and purine. These are: N-^^^^ â N^ -N ,^ -NH liyriiiiidine punnp The four pvrimidincs most abiuulant in nucleic acids arc: H.,N ,1^ N. ',0 H '.O NH .NH CHg H ,N. .-^ O Nâ â :y NH cytosine uracil thymine H.,Nr^^-V^" 5 - methylcytosine One other, hydroxymethylcytosine, has been isolated in the nucleic acids from certain bacterial viruses. The most abundant purines are: ^ .N. NH. NH adenine guanine with others known from metabolic processes. These bases are con- densed by way of the semiacetal forms of D-ribose and D-deoxyribose to form ribonucleosides and deoxyribonucleosides, respectively. Not all possible combinations are known. Cytosine, uracil, adenine, and guanine are found attached to ribose and cytosine, methylcytosine, hydroxymethylcytosine, thymine, adenine, and guanine with the deoxy sugar. The linkages are similar for all pyrimidines on the one hand and for the purines on the other. Thus, the structures of the nucleo- sides may be illustrated by: ,N. H.,N ^ jO OH OH I /I l\l NâC^ H H ..C NH, H 0' CH,,OH. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Mallette, M. Frank (Manney Frank), 1917-. New York, Wiley
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