chapter 4

• Nucleic Acids


  Specialized, macromolecules for storage, transmission, and use of genetic information
• DNA


  Deoxyribonucleic acid (double-stranded (ds) helix)
• RNA


  Ribonucleic acid (single-stranded (ss), self-bonds (i.e., forms intramolecular H-bonds))
• Composition of Nucleic Acids

  • DNA uses deoxyribose
  • RNA uses ribose
• Nucleoside


  Pentose sugar and a nitrogenous base
• Nucleotides


  Pentose sugar, a phosphate group, and a nitrogenous base
• PURINES AND PYRIMIDINES are the BASES to form NUCLEOSIDES AND NUCLEOTIDES
• Remember: Purina is AG
• Nucleic Acid Synthesis (Polymerization)

  1. Nucleotides are linked by phosphodiester linkages

  2. Phosphate groups link carbon 3' in one sugar to carbon 5' in another sugar

  3. Nucleic acids grow in the 5'-to-3' direction
• DNA STRUCTURE AND FUNCTION

  • Two strands-double helix
  • Replication - process for copying DNA to transfer genetic information to next generation
• RNA STRUCTURE AND FUNCTION


  • Single-stranded
  • Ribose-phosphate backbone
  • May be 3-D structure (hydrogen bonds within the ss molecule)
  • Complementary base pairing between RNA and DNA
  • KEY EXCEPTION: Uses uracil as the pyrimidine binding with adenine
• NUCLEIC ACID FUNCTIONS IN BIOLOGY


  • Replication - making a complete copy of the DNA (genome) before cell division
  • Transcription - making mRNA from DNA template
  • Translation - making protein from mRNA
  • Transcription plus translation = gene expression
• DNA TRANSCRIPTION to RNA (mRNA)

  1. GENE 1

  2. GENE 2
• NON-NUCLEIC ACID FUNCTIONS OF NUCLEOTIDES


  • ATP - energy source for ALMOST ALL biochemical reactions
  • GTP - energy source in protein synthesis (translation)
  • cAMP - Signaling molecule; NOT an energy source! Essential to the action of hormones and information transmission in the nervous system