• Nucleic acids?such as?DNA?(deoxyribonucleic acid) and?RNA?(ribonucleic acid) are?macromolecules?(giant molecules)
• Like proteins (polypeptides) and carbohydrates (polysaccharides), these nucleic acids are?polymers?(‘poly’ meaning ‘many’)
• This means they are made up of many similar, smaller molecules (known as?subunits?or?monomers) joined into a long chain
• The subunits that make up DNA and RNA are known as?nucleotides
• Therefore DNA and RNA can also be known as?polynucleotides

Nucleotides

• Nucleotides are made up of three components:
  • A?nitrogen-containing base?(also known as a nitrogenous base)
  • A?pentose sugar?(containing 5 carbon atoms)
  • A?phosphate group

The basic structure of a nucleotide

Nucleotide structure table

The nucleotides found in DNA and RNA

ATP

• Adenosine triphosphate?(ATP) is the energy-carrying molecule that provides the energy to drive many processes inside living cells
• ATP is?another type of nucleic acid?and hence it is structurally very similar to the nucleotides that make up DNA and RNA
• It is a?phosphorylated?nucleotide
• Adenosine (a nucleoside) can be combined with one, two or three phosphate groups
  • One phosphate group =?adenosine monophosphate?(AMP)
  • Two phosphate groups =?adenosine diphosphate?(ADP)
  • Three phosphate groups =?adenosine triphosphate?(ATP)

The structure of AMP, ADP and ATP

• The?nitrogenous base?molecules that are found in the nucleotides of DNA (A, T, C, G) and RNA (A, U, C, G) occur in?two structural forms:?purines?and?pyrimidines
• The bases?adenine?and?guanine?are?purines?– they have a?double ring structure
• The bases?cytosine,?thymine?and?uracil?are?pyrimidines?– they have a?single ring structure

The molecular structures of purines and pyrimidines are slightly different