A diatomic molecule consists of one F atom and one Cl atom. Consult the Periodic Table. Seemingly different living things are remarkable alike in many regards at the molecular level. More than 2 billion. More than 4 billion.
Carbohydrates contain hydroxyl groups.
Amino acids chain to form proteins. RNA and DNA are proteins. Nucleotides chain to form nucleic acids. Nucleotides contain organic bases. RNA is usually double stranded.