Gq Protein Signaling Quiz

An Introduction to Medicinal Chemistry - Chapter 6: Drug Targets Nucleic Acids (DNA & RNA)

• This chapter focuses on drug targets within nucleic acids, specifically DNA and RNA.

1. Deoxyribonucleic Acid (DNA)

• 1.1 Primary Structure:

  • DNA's fundamental units are nucleotides.
  • Each nucleotide comprises a phosphate group, a sugar (deoxyribose), and a nitrogenous base.
  • The bases are: adenine (A), guanine (G), cytosine (C), and thymine (T).
  • Nucleotides link via phosphodiester bonds, creating a sugar-phosphate backbone.
  • Bases are attached to the sugar in an apparent random sequence.
  • The sugar-phosphate backbone is constant, but the specific bases vary along the chain.
  • The primary structure defines the sequence of bases (A, T, C, G).
  • Nucleosides are formed by linking sugar to the base (no phosphate).
  • Deoxyadenosine, deoxyguanosine, deoxythymidine, and deoxycytidine are important components.

• 1.1 Primary Structure - Building Blocks:

  • Nucleotides consist of deoxyribose sugar, phosphate group, and nitrogenous bases.
  • Deoxyadenosine phosphate, deoxyguanosine phosphate, deoxythymidine phosphate, and deoxycytidine phosphate are the four key nucleosides.

• 1.1.1 Primary Structure - further details:

  • Nucleotide = phosphate + sugar + nucleic acid base
  • Nucleosides = sugar + nucleic acid base
  • Sugars are deoxyribose.
  • Bases are adenine, guanine, cytosine, and thymine.

• 1.1 Primary Structure - further details

  • Nucleosides are formed by linking sugar to base
  • Sugars are deoxyribose.
  • Bases are adenine, guanine, cytosine, and thymine

• 1.1 Primary Structure - overview:

  • Nucleotides are the fundamental units of DNA.
  • Each nucleotide contains a deoxyribose sugar, a phosphate group, and a nitrogenous base.
  • Nucleosides lack the phosphate group.

• 1.1 Primary Structure- Nucleotides Continued:

  • Key Components: Deoxyribose, phosphate, the nitrogenous bases (adenine, guanine, cytosine, thymine) are the constituent parts of each nucleotide.

• 1.1 Primary Structure - detailed structure:

  • Visual representation of deoxyadenosine, deoxyguanosine, deoxythymidine, and deoxycytidine phosphate chemical structures are provided.

• 1.1 Primary Structure- Nucleotide overview

  • Nucleotides are used to construct the primary structure of DNA.
  • The order of bases forms a specific genetic code.

• 1.2 Secondary Structure - Double Helix:

  • The sugar-phosphate backbone is ionised and faces outward.
  • Bases point inward, paired via hydrogen bonds (A-T or G-C).
  • Purine pairs with pyrimidine - ensuring constant helix diameter.
  • The two DNA strands are complementary.

• 1.2 Secondary Structure - Double Helix- summary

  • DNA's double helix structure is crucial for its function and stability.
  • The DNA backbone and base-pairing interactions dictate its 3D structure.

• 1.2 Secondary Structure- details

  • Complementary base pairing maintains the DNA structure.
  • A-T and G-C pairing are maintained by hydrogen bonds.

• 1.3 Tertiary Structure - Supercoiling:

  • The double helix coils into a 3D shape, which is termed supercoiling.
  • Unravelling during replication creates strain.
  • Enzymes like topoisomerases relieve this strain by temporarily cleaving the DNA chain.

• 1.3 Tertiary Structure - details

  • Supercoiling occurs as a result of DNA's inherent characteristics and its interactions with its surroundings.
  • Topoisomerases play a critical role in managing these complexities.

• 1.4 Action of topoisomerase II:

  • Relieves strain on the DNA helix.
  • Temporarily cleaves the DNA chain.
  • Creates a gap and passes an intact strand through the break.
  • The break is then resealed.
  • Tyrosine residues in the enzyme are crucial for the chain breaking and rejoining process.

• 1.4 Action of Topoisomerase II - further details

  • Tyrosine residues catalyse DNA cleavage and rejoining.

• 1.4 Mechanism of chain cutting:

  • Shows the process of DNA strand cleavage and resealing.
  • This process is essential for DNA replication and transcription and is critically regulated by enzymes such as topoisomerase II.

• 1.5 Replication:

  • DNA replication is the process of making an identical copy of a DNA molecule.
  • The double helix unwinds as the template for a new DNA structure.

2. Ribonucleic Acid (RNA)

• 2.1 Primary Structure:

  • Similar to DNA, RNA comprises nucleotides.
  • Ribose sugar, instead of deoxyribose.
  • Uracil (U) instead of thymine (T).

• 2.1 Primary Structure - further details:

  • RNA nucleotides contain a ribose sugar, a phosphate group, and one of the nitrogenous bases ( adenine, guanine, cytosine, or uracil).
  • The ordering of bases creates the unique RNA sequence.

• 2.2 Secondary Structure:

  • RNA can fold into complex secondary structures.
  • Base pairing with in some areas creates helical regions, like in t-RNA.

• 2.3 Tertiary Structure:

  • RNA molecules exhibit diverse tertiary structures.
  • Three types of RNA (mRNA, tRNA, rRNA) are vital in protein synthesis.

• 2.4 Transcription:

  • DNA is copied into mRNA.
  • The primary structure of mRNA carries the genetic information for protein sequence from the nucleus.

• 2.5 Translation - protein synthesis:

  • mRNA sequence is used to build proteins.
  • Ribosomes read mRNA, tRNA moves corresponding amino acids.
  • Amino acids link to form a polypeptide to construct protein.
  • The ribosomes are the protein synthesis machinery.
  • tRNA delivers specific amino acids.
  • Translation occurs on the ribosomes in the cytoplasm.

Summary of both DNA & RNA

• Both DNA and RNA are nucleic acids.
• Both carry genetic information.
• DNA is double-stranded, RNA is usually single-stranded.
• Different bases, hence different biological functions.
• DNA primarily stores genetic instructions, RNA plays vital roles in protein synthesis and other cellular processes.