Nucleotides

• functions:

  • building block of DNA and RNA
  • Used in energy transduction reactions
  • ATP act as activated carriers of carbohydrates, amino acids, lipids, sulfates, and methyl groups
  • structural components of coenzymes (coenzyme A, NAD, flavin adenin dinucleotide (FAD))
  • regulators of key intracellular enzymes (cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP))
  • perform a variety of intracellular functions in energy transduction reactions
• origin/synthesis

  • from small organic molecules available in cells
  • through salvage pathways that recycle nitrogen bases
• Nucleotides are composed of:

  1. nitrogen base (purine/pyrimidine)
  2. cyclic pentose
  3. phosphate groups

  nucleoside: nitrogen base + pentose

  nucleotide: nucleoside + phosphate
• DNA vs RNA

  • RNA (ribonucleic acid) has ribose group attached to OH at 2’ carbon atom
  • DNA (deoxyribonucleic acid) has ribose group attached to H at 2’ carbon atom
  • Found in both: 2 purines: adenine, guanine, 3 pyrimidines: cytosine, thymine, uracil
  • Only in DNA: thymine (methyl derivative of uracil)
  • Only in RNA: uracil
• Nucleotide groups:

  • purines: adenine, guanine
  • pyrimidine: cystosine, uracil (RNA only), thymine (DNA only)
• Requirement for biosynthesis of RNA

  • 2 purines
  • Nucleoside triphosphates (NTPs or rNTPs)
  • Carbon dioxide
  • Aspartate
  • 5-phosphoribosyl-1-pyrophosphate
  • For thymine nucleotides: tetrahydrofolate derivatives