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Why are DNA and RNA are acids?

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Why are DNA and RNA are acids?

Postby snemani1177 » Wed Mar 10, 2010 1:07 am

Why are DNA and RNA are acids? Is that due to the phosphate group.
'Molecular biology by Phil Turner at al' states that "At neutral pH, each phosphate group has a single negative charge. This is why nucelic acids are termed acids; they are the anions of strong acids".So, what I am not clear about is why negative charge brings acidity? Please give me a detailed answer.

Thanks.
Sanjeeva Nemani.
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Postby plasmodesmata11 » Wed Mar 10, 2010 1:14 am

yeah, it's because of the phosphate groups
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Postby snemani1177 » Wed Mar 10, 2010 1:41 am

So, does HCl has negative charge as it is a strong acid.
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Postby JackBean » Wed Mar 10, 2010 6:43 am

the acid is definied (by Arrhenius and Broensted) as substance able to release proton (H+), thus becoming anion (H3PO4 -> (H2PO4)-; HCl -> Cl-)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Re: Why are DNA and RNA are acids?

Postby jonmoulton » Wed Mar 10, 2010 5:56 pm

HCl, in water, is H+ and Cl-. The phosphate of a nucleic acid backbone in water, is (sugar-PO4-sugar)- and has some H+ counterion dissolved in the water. However, just as we write HCl as an uncharged molecule and call it an acid (because it dissociates in water releasing an H+), we could write that backbone phosphate moiety in its uncharged form (sugar-PO3(OH)-sugar) and call it an acid, because when the protonated molecule is dissolved in water it dissociates and releases an H+.
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