1. Case Western Reserve University
Organic Chemistry
4th Edition
Paula Yurkanis Bruice
Chapter 27
Nucleosides,
Nucleotides,
and
Nucleic Acids I
Irene Lee
Case Western Reserve University
Cleveland, OH
©2004, Prentice Hall

2. Nucleic Acids

3. In nucleic acid, the phosphate group is phosphodiester

4. The Bases in Nucleic Acids
Adenine, guanine, cytosine, and thymine are found in
DNA
Adenine, guanine, cytosine, and uracil are found in RNA

5. Nucleosides = Base + Sugar

6. Nucleotides = Base + Sugar + Phosphate

8. Different Forms of Nucleotides

9. ATP as a Chemical Energy Source
The energy released from ATP hydrolysis is used to drive
the phosphorylation of D-gluose (coupled reactions)

10. Breakage of the Phosphoanhydride Bond in ATP

11. Without ATP, the OH– group cannot be displaced

12. This reaction does not occur without ATP because of the
poor leaving group

13. Phosphoryl Transfer Reaction Mechanism I

14. Phosphoryl Transfer Reaction Mechanism II

15. Phosphoryl Transfer Mechanism III

16. Pyrophosphate can be further hydrolyzed to phosphate

17. Why is the hydrolysis of a phosphoanhydride bond so
exergonic?

18. 1. Greater electrostatic repulsion in ATP
2. More solvation in the products
3. Greater resonance stabilization in the products

19. The interactions between ATP, Mg2+, and arginine and
lysine residues at the active site of an enzyme
Since all the negative charges in ATP are neutralized,
ATP is readily approached by nucleophiles

20. Other Important Nucleotides
Cyclic AMP serves as a link between several hormones
and certain enzymes that regulate cellular function

21. The Nucleic Acids
Biosynthesis of DNA
occurs in the 5’ ’
direction

22. Complementary Base Pairing in DNA

24. The sugar–phosphate is on the outside, and the bases
are on the inside

25. The DNA Double Helix

26. Hydrolysis of RNA

27. The Three Helical Forms of DNA
Hydrogen bonding and base stacking interactions hold
the DNA helix together

29. Replication of DNA

30. Transcription of DNA
A stretch of bases representing a portion of a gene is
called an exon
A stretch of bases that contain no genetic information is
called an intron
mRNA is spliced prior to leaving the nucleus

31. A Transfer RNA

32. The Proposed Mechanism for Aminoacyl-tRNA Synthetase

33. The Substrate-Binding Site for tRNAHis

34. A protein is synthesized from its N-terminal end to its
C-terminal end
Each amino acid is specified by a three-base sequence
known as the genetic code

35. Translation

37. Why does DNA contain thymine instead of uracil?
The synthesis of thymine is energetically expensive

38. Because cytosine can be converted to uracil ….
Having T’s in place of U’s in DNA allows the U’s that are
found in DNA to be recognized as mistakes

39. DNA Sequencing

41. Laboratory Synthesis of DNA

43. Oligonucleotide
Synthesis with
Phosphoramidites

44. The amino groups of the bases must be protected

45. Removal of the Protecting Group by Ammonia

46. Utilization of H-phosphate
monomer to synthesize DNA strand

49. Hoogsteen Base Pairing