Overview of Nucleic Acids Structure

Oct 25, 2024

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Notes on Nucleic Acids Lecture

Introduction to Nucleic Acids

  • Nucleic acids are biopolymers made up of nucleotides.
  • Two main functions:
    • Hold genetic information.
    • Perform various functions (details to be discussed later).
  • Two types of nucleic acids:
    • DNA (Deoxyribonucleic Acid)
    • RNA (Ribonucleic Acid)

Definition of Nucleic Acids

  • Biopolymers: Synthesized in biological systems, not synthetic.
  • Made of monomers known as nucleotides.

Structure of Nucleotides

  • Components of a nucleotide:
    1. Phosphate group
    2. Sugar (5-carbon sugar)
    3. Nitrogenous base

Sugar Structure

  • Types of sugars:
    • Pentoses (5-carbon): Ribose and Deoxyribose.
    • Differences:
      • Ribose: Contains hydroxyl group (–OH) at C2.
      • Deoxyribose: Lacks hydroxyl group at C2 (only has a hydrogen).
    • Importance of naming:
      • Deoxyribose: "Deoxy" means removal of oxygen.
      • Ribose corresponds to RNA, Deoxyribose corresponds to DNA.

Phosphate Group

  • Composed of:
    • 1 Phosphorus atom (central)
    • 4 Oxygen atoms (negatively charged)
  • Polar molecule due to highly ionized oxygen.
  • Same phosphate group found in ATP (Adenosine Triphosphate).

Nitrogenous Bases

  • Contain nitrogen and form ring-like structures.
  • Two types:
    • Purines (double-ring): Adenine (A), Guanine (G)
    • Pyrimidines (single-ring): Thymine (T), Cytosine (C), Uracil (U)
  • Size difference is significant for base pairing in DNA.

Bonding in Nucleotides

  • Glycosidic bond: Links sugar and nitrogenous base.
  • Ester bond: Links sugar and phosphate group.

Formation of Polynucleotides

  • Nucleotides link to form a polynucleotide chain:
    • Sugar-phosphate backbone.
    • Nitrogenous bases project from the backbone.
  • In RNA, the sugar is ribose; in DNA, it’s deoxyribose.

DNA Structure

  • Base pairing rules:
    • Adenine (A) pairs with Thymine (T)
    • Guanine (G) pairs with Cytosine (C)
  • DNA structure resembles a double helix:
    • Sugar-phosphate backbone as the "sides of the ladder".
    • Nitrogenous bases as the "rungs" of the ladder.

Conclusion

  • This lecture was an introduction to nucleic acids.
  • Future topics to cover:
    • Detailed structures of DNA and RNA
    • Processes: DNA replication, transcription, translation
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