Final answer:
A) DNA molecule. In a DNA molecule, phosphoric acid forms a phosphodiester bond with hydroxyl groups of sugars between phosphate at C-5' and OH at C-3', creating the DNA backbone with a chain directionality from 5' to 3'.
Step-by-step explanation:
In a DNA molecule, phosphoric acid is joined to two alcohols (hydroxyl groups of sugars) by an ester linkage on both sides, forming between the phosphate group at the C-5' and the OH group on C-3' position. This link is known as a phosphodiester bond and is essential for creating the backbone of the DNA structure. Nucleotides bind together in a chain through these phosphodiester bonds, where the 5'-end of the chain has a free phosphate group, and the 3'-end has a free hydroxyl group.
The sugar involved in this process is deoxyribose in DNA, each sugar molecule being connected to a phosphate group to form the DNA backbone. Thus, in nucleic acids, the phosphate residue of one nucleotide is linked to the hydroxyl group of the next nucleotide's sugar, contributing to the chain's directionality. These bonds allow the DNA molecule to have a stable, long chain that encodes genetic information.