Pyrimidine Moieties in Animals, Plants, and Bacteria 



105 



Ribosomal-RNA and Total Cellular RNA 



Ribosomal RNA comprises the bulk of the RNA of cells (approxi- 

 mately 80 per cent). The ribosomes, particles consisting of about 

 half protein and half RNA, are the organelles where amino acids 

 are assembled into protein chains. Ribosomal-RNA seems to con- 

 sist of two components having sedimentation constants of about 



TABLE XI 



Guanine and Cytosine Content of Ribonucleic 

 Acids from Various Organisms 



