Nucleotides (Cambridge (CIE) AS Biology): Revision Note

Nucleotide structure

• Nucleic acids such as DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are macromolecules

  • Like proteins (polypeptides) and carbohydrates (polysaccharides), these nucleic acids are polymers 

  • 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

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 nucleotide and hence it is structurally very similar to the nucleotides that make up DNA and RNA

• It is a phosphorylated nucleotide

Purines & pyrimidines

• 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

  • This means that they have a double-ring structure

• The bases cytosine, thymine, and uracil are pyrimidines 

  • These bases have a single-ring structure