NUCLEIC ACID

• discovered in 1869 by Swiss Physiologist Friedrich Miescher.
• unbranched polymer containing monomers called nucleotides; repeating unit is nucleotides.
• end products are protein or amino acids
• Nucleotide → three-subunit molecule; building block of nucleic acids. → contains a pentose sugar (monosaccharide), phosphate group, and nitrogen base (heterocyclic base).
• Pentose Sugar → 5 carbons → RNA and DNA differ in the identity of the sugar unit in their nucleotides; ribose for RNA – hence the R in its name, deoxyribose for DNA – hence the D in its name (deoxy means “without oxygen). → base is attached at Carbon 1 (C1), while phosphate group is attached at Carbon 5 (C5).
• → in terms of structure, RNA and DNA only differs at Carbon 2 (C2). −OH for ribose; −H for deoxyribose.
• Nucleic Acid Backbone → phosphate – sugar; found in all nucleic acids.
• Nitrogen Base → 5 bases; 3 are derived from pyrimidine – thymine (T), cytosine (C), and uracil (U); 2 are from purines – adenine (A), and guanine (G).
• pyrimidine – monocyclic (single ring) base with a six-membered ring;
• purines – bicyclic (double ring) base with fused five and six-membered rigs.
• → adenine (A), guanine (G), and cytosine (C) are found in both RNA and DNA.
• pyrimidines and purines both contain amine functional groups
• uracil (U) – found only in RNA.

  thymine (T) – found only in DNA.
• Pyrimidine Derivatives


  thymine (T), cytosine (C), and uracil (U)
• Purine Derivatives→ adenine (A) and guanine (G).
• Phosphate → third component of nucleotide; derived from phosphoric acid.
• H3PO4 (phosphoric acid)

  HPO4 2- (hydrogen phosphate ion)
• Nucleoside

  two-subunit molecule composed of pentose sugar bonded with a nitrogen base
• Nucleoside → two-subunit molecule composed of pentose sugar bonded with a nitrogen base
• DNA Nomenclature


  Adenine deoxyadenosine deoxyadenosine 5’- monophosphate

  Guanine deoxyguanosine deoxyguanosine 5’- monophosphate

  Cytosine deoxycytidine deoxycytidine 5’- monophosphate

  Thymine deoxythymidine deoxythymidine 5’-
• RNA Nomenclature


  Adenine adenosine adenosine 5’- monophosphate Guanine guanosine guanosine 5’- monophosphate Cytosine cytidine cytidine 5’- monophosphate Uracil uridine uridine 5’- monophosphate
• nucleoside


  – sugar and nitrogen base
• backbone


  sugar and phosphate
• nucleotide


  all tree (sugar, phosphate, base).
• Ribonucleic Acid


  nucleotide polymer in which each of the monomers contains a ribose, a phosphate group, and one of the nitrogen bases adenine, cytosine, guanine, or uracil.

  backbone – alternating phosphate and ribose
• Deoxyribonucleic Acid


  nucleotide polymer in which each of the monomers contains deoxyribose, a phosphate group, and one of the nitrogen bases adenine, guanine, cytosine, or thymine.

  backbone – alternating phosphate and deoxyribose.
• Primary Nucleic Acid Structure


  sequence in which nucleotides are linked together in a nucleic acid
• phosphodiester lingkage.


  each nonterminal phosphate group of the sugarphosphate backbone is bonded to two sugars molecules through a 3’, 5’
• DNA


  deoxyribonucleic acid → double helix / double stranded

  location: inside the nucleus

  → replication / duplication

  → genetic information

  → amounts of complementary bases are always equal (A% = T% and C% = G%)

  → two strands are anti-pallarel; run in opposite directions; one runs in the 5’-to-3’ direction and vice versa.
• Base Pairing


  one small base (pyrimidine) and one large base (purine) can fit within the helix interior.

  → hydrogen bonding is stronger with A-T and G-C
• Complementary Bases


  are pairs of bases in a nucleic acid structure that is hydrogen-bonded to each other. → complementary bases: A ↔ T and G ↔ C.
• DNA replication


  – biochemical process by which DNA molecules produce exact duplicates of themselves
• DNA ligase


  connects the segments latter.
• DNA helicase 


  enzyme that breaks the hydrogen bond between complementary bases.
• replication fork


  – point at which the DNA double helix is unwinding, which is constantly changing (moving).
• antimetabolites


  drugs in which they inhibit DNAreplication process.
• histones 


  proteins; form structural units that provide the most stable arrangement for the long DNA molecules.
• Chromosomes


  histones – proteins; form structural units that provide the most stable arrangement for the long DNA molecules.
• histone-DNA complexes; individual DNA molecule bounded to a group of proteins.

  chromosomes
• Protein Synthesis


  under the direction of DNA molecules.

  → proteins are responsible for the formation of skin, hair, enzymes, hormones, and so on.