Nucleic acids

Basic Structure:

All nucleic acids have to the same basic structure:

• A pentose sugar; this sugar may arranged as a straight chain aldehyde or in a cyclic conformation called a furanose ring. The furanose ring is much more stable than the aldehyde because it is less rigid and therefore more able to withstand attack; these two conformations are typically found in equilibrium with each other.
• A nitrogenous base; this may be adenine, guanine, cytosine, thymine or uracil. Both adenine and guanine are purines and have two ring structures. Cytosine, thymine and uracil are pyrimidines and contain only one ring structure
• A phosphate group; this is typically attached to the 5' carbon and makes the molecule reactive. PO4(2-) has 2 reactive oxygen ions which are negatively charged

Nucleic acids as energy currency:

The most common energy molecule is ATP. The bonds between each phosphate group are called anhydride bonds and the bond between the primary phosphate group and the furanose ring is called an ester bond

Hydrolysis of the ester bond yields 14kJ of energy and hydrolysis of the anhydride bond yields 30kJ of energy. Both of these reactions therefore yield relatively little energy. ATP is able to generate far more energy by donating its phosphoryl, pyrophosphoryl and adenylyl groups.

Similarly, the reaction ATP -> ADP +Pi is actually a two step reaction, that is coupled with another reaction. The purpose of the phosphate group is to increase the reactivity of another molecule; the phosphate group therefore binds to this molecule to create a reactive intermediate.   

Nucleic acids as co-factors:

Co-factors are consumed with…