Nucleic Acids Overview

Nucleic Acids: In-Depth Notes

Components of Nucleic Acids

• Types of Nucleic Acids:

  • Deoxyribonucleic acid (DNA)
  • Contains several million nucleotides
  • Unbranched polymer
  • Ribonucleic acid (RNA)
  • Contains several thousand nucleotides
  • Unbranched polymer

• Nucleotides Composition:

  • Each nucleotide consists of three main components:
  • Base (contains nitrogen)
  • Five-carbon sugar
  • Phosphate group

Bases in Nucleic Acids

• Base Types:
  • Pyrimidines
  • Single ring structure containing two nitrogen atoms
  • Purines
  • Double ring structure, each containing two nitrogen atoms

Bases in DNA

• Pyrimidines:
  • Cytosine (C)
  • Thymine (T)
• Purines:
  • Adenine (A)
  • Guanine (G)

Bases in RNA

• Pyrimidines:
  • Cytosine (C)
  • Uracil (U)
• Purines:
  • Adenine (A)
  • Guanine (G)

Pentose Sugars

• Sugar Types:
  • RNA: Ribose
  • DNA: Deoxyribose (lacks O atom on C2′)
• Carbon Numbering:
  • Carbon atoms in the sugars are numbered with primes to distinguish them from base atoms

Nucleosides and Nucleotides

• Nucleoside:

  • Composed of a nitrogen-containing base and a sugar (ribose or deoxyribose)
  • Base linked by a β-N-glycosidic bond to C1′ of the sugar

• Nucleotide:

  • Formed by adding a phosphate group to the C5′ -OH group of a nucleoside

Examples:

• AMP (Adenosine Monophosphate): Base + Ribose + 1 Phosphate
• ADP (Adenosine Diphosphate): AMP + 1 Additional Phosphate
• ATP (Adenosine Triphosphate): ADP + 1 Additional Phosphate

Primary Structure of Nucleic Acids

• Phosphodiester Bonds:
  • Nucleotides are joined by phosphodiester bonds.
  • The 3’-OH group of the sugar in one nucleotide links to the phosphate group on the 5’-carbon of the sugar of the next nucleotide.

Key Characteristics:

• Primary structure defined by the unique sequence of bases, often represented by base letters.
• The sequence is read from the sugar with the free 5’ phosphate to the sugar with the free 3’ -OH group.
  • Example: 5’ A C G T 3’

Primary Structure of RNA

• RNA primary structure involves bases A, C, G, and U connected by 3’, 5’ phosphodiester linkages.