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Understanding Nucleic Acids in Biochemistry

Jan 14, 2025

Biochemistry: Nucleic Acids Lecture

Introduction to Nucleic Acids

  • Two forms: DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid)
  • DNA: Double-stranded, forms an alpha-helix
  • RNA: Single-stranded

Location and Function

  • DNA:
    • Found mostly in the nucleus (eukaryotes)
    • Function: Stores genetic information, "library of the cell"
  • RNA:
    • Located outside the nucleus
    • Function: Transfers genetic information, synthesizes protein
    • Types: Ribosomal RNA (rRNA), Transfer RNA (tRNA), Messenger RNA (mRNA)

Nucleic Acids Composition

  • Both are polymers made of monomers called nucleotides
  • Nucleotide components:
    • Pentose sugar (5-carbon sugar)
    • Nitrogenous base
    • Phosphate group

Sugars in Nucleic Acids

  • DNA: Deoxyribose sugar (lacks hydroxyl group on carbon 2)
  • RNA: Ribose sugar (contains hydroxyl group on carbon 2)

Nitrogenous Bases

  • DNA: Adenine (A), Guanine (G), Cytosine (C), Thymine (T)
  • RNA: Adenine (A), Guanine (G), Cytosine (C), Uracil (U)
  • Common Exam Question: Uracil is found in RNA, Thymine is found in DNA

Categories of Nitrogenous Bases

  • Purines (two rings): Adenine, Guanine
  • Pyrimidines (one ring): Cytosine, Thymine, Uracil

Structures of Nitrogenous Bases

  • Purines:
    • Adenine: Has NH2 group
    • Guanine: Has NH2 and carbonyl group
  • Pyrimidines:
    • Thymine: Two carbonyl groups
    • Uracil: Similar to thymine but without a methyl group
    • Cytosine: Has one NH2 group and a carbonyl group

Nucleosides vs Nucleotides

  • Nucleoside: Sugar + Base
  • Nucleotide: Sugar + Base + Phosphate
  • Nomenclature Example:
    • Cytosine (Base) → Cytidine (Nucleoside) → Cytidylate (Nucleotide)

Naming Nucleosides and Nucleotides

  • Adenine → Adenosine → Adenylate
  • Guanine → Guanosine → Guanolate
  • Thymine → Thymidine → Deoxythymidylate (for DNA)

DNA Structure

  • Complementary Strands: Pairing rules (A-T, C-G)
  • Hydrogen Bonds: A-T pairs have 2 bonds, C-G pairs have 3 bonds
  • Sugar-Phosphate Backbone: 3',5' phosphodiester linkage
  • Anti-parallel Strands: 5' to 3' direction opposite in the two strands

Application

  • Write complementary DNA strand using base pairing rules
  • Example: Complementary to 5'-ATCG-3' is 3'-TAGC-5'

Conclusion

  • Key points about nucleic acids: DNA vs RNA, structure, function, and composition
  • Importance in genetic information storage and transfer

Additional Resources: For further review on hydrogen bonds and intermolecular forces, search for instructional videos or consult textbooks.

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