Michigan State University

Nucleic acids are macromolecules that are composed of subunits called nucleotides.  They are responsible for the transfer of genetic information from an organism's genome and turning it into proteins.  Nucleic acids exist in two forms:

- deoxyribonucleic acid (DNA)
- ribonucleicacid (RNA)

Nucleic acids are built using nitrogen, and thus need a nitrogen source to undergo nitrogen fixation

Nucleic Acids

• DNA is the hereditary material of the cell  
• It is mostly formed in antiparallel DNA strands in a double helix with a 5' and 3' end. 

• DNA contains major and minor grooves. 

• DNA is formed from hydrogen bonds between the base pairs adenine and thymine and cytosine and guanine bases, respectively.

Deoxyribonucleic Acid (DNA)

- Ultimate source: atmospheric nitrogen gas -> to be used, it must be split to make ammonium
- Nitrogen fixation: split N2 and reduce it to NH4+
- Mostly newly-fixed nitrogen (60%) is from archaea and bacteria
- Other sources: 15% from lightning, UV, 25% from industry
- Plants take in nitrites and nitrates and reduce them with electrons from reduced cofactors to make ammonium for synthetic reactions
- Higher organisms (like humans) ingest nitrogen-containing compounds


Nitrogen Sources

- Some bacteria and archaea are diazotrophic (nitrogen-fixing) splitting gaseous, atmospheric nitrogen and reducing it to ammonia
- The triple nitrogen bond is difficult to break because of the instability of highly reactive, high-energy intermediates in the pathway
- After intermediates are created, the reaction is downhill in terms of energy, making it easy, but getting there can be difficult
- The reactions require special catalysts (enzymes) not found in higher organisms
- Energetically expensive process
- Requires 16 ATP per mole of N2 split and reduced
- Split N2 - reduce to NH3
- N2 + 10H+ + 8e- -> 2 NH3+ + H2
Ferredoxin, Nitrogenase
Two parts - reductase and nitrogenase


Nitrogen Fixation occurs in diazotrophic organisms

RNA is involved in protein synthesis and regulation. It also has catalytic properties.
RNA is typically found in the single stranded form.
RNA is formed from hydrogen bonds between the base pairs adenine and uracil and cytosine and guanine bases, respectively.

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