What are the two main types of nucleic acids in living organisms?

The two main types of nucleic acids in living organisms are RNA and DNA. DNA, or deoxyribonucleic acid, serves as the hereditary blueprint for organisms, containing the instructions needed for the development, functioning, growth, and reproduction of all known living organisms and many viruses. It is structured in a double helix formation and composed of nucleotide pairs, which include adenine, thymine, cytosine, and guanine.

RNA, or ribonucleic acid, plays critical roles in the synthesis of proteins and the expression of genes. Unlike DNA, RNA is usually single-stranded and contains uracil in place of thymine. There are several types of RNA, including messenger RNA (mRNA), which carries the genetic information from DNA to the ribosome, and transfer RNA (tRNA), which helps assemble amino acids into proteins.

The other options include components that are essential to biological functions but do not classify as nucleic acids. Proteins and carbohydrates, while critical for various metabolic processes and energy storage, are not nucleic acids. Lipids, although important for cell membranes and energy storage, also do not fit into the category of nucleic acids. Thus, the correct answer highlights the two fundamental molecules responsible for