So we have these two strands of DNA molecules running in an antiparallel fashion and bonding via hydrogen bonds and Vanderbilt forces. Now, what about the other type of nucleic acid? So we also have ribonucleic acids, RNA molecules. The question is what exactly is the structure of these RNA molecules? Well, unlike DNA molecules which exist in a double stranded form, RNA molecules inside our cells exist mostly as single strands of nucleotides. But these single trans of nucleotides under the conditions found in our cells usually twist and fold into a well defined threedimensional structure.