DNA, or deoxyribonucleic acid, is considered acidic due to the presence of phosphate groups within its structure. These phosphate groups are similar in structure to phosphoric acid, which readily donates a proton (H+) in solution. This property, by definition, makes DNA a Brønsted acid.
The phosphate groups are linked together by sugar molecules to form the sugar-phosphate backbone of DNA. This backbone is negatively charged due to the presence of the phosphate groups, which contributes to DNA's acidic nature.
In essence, the phosphate groups in DNA act like tiny, acidic "batteries" that can release hydrogen ions (H+) into their surroundings, making the solution more acidic.
