1. Macromolecules Part IV: Nucleic Acids Informational molecules

3. Introduction: Nucleic Acids The amino acid sequence of a polypeptide is programmed by a gene A gene consists of regions of DNA, a polymer of nucleic acids (100’s to 1000’s) DNA (and their genes) is passed by the mechanisms of inheritance Only molecule that can produce identical copies of themselves

4. There are two types of nucleic acids:  ribonucleic acid (RNA)  deoxyribonucleic acid (DNA) DNA provides direction for its own replication DNA also directs RNA synthesis and, through RNA, controls protein synthesis Nucleic acids store and transmit hereditary information

5. Roles of DNA  Protein expression (Phenotypes)  Inheritance (Genotypes) 3.Evolution (Mutations) 

6. Nucleotides Nucleic acids are polymers of monomers called nucleotides Each nucleotide consists of three parts:  a nitrogen base  a pentose sugar  a phosphate group

7. Sugar-Phosphate “Backbone”

8. Nucleic Acids Polynucleotides are synthesized by connecting the sugars of one nucleotide to the phosphate of the next with a phosphodiester link The phosphodiester links create a repeating backbone of sugar-phosphate units with the nitrogen bases as appendages

9. RNA DNA Phosphodiester link

10. Nucleotides The nitrogen bases, rings of carbon and nitrogen, come in two types:  Purines  pyrimidines Pyrimidines have a single six-membered ring The three different pyrimidines that differ in the atoms attached to the ring:  cytosine (C), thymine (T), and uracil (U) Purines have a six-membered ring joined to a five-membered ring and there are two types:  adenine (A) and guanine (G)

11. Purine Bases Adenine and guanine are purines Adenine and guanine are purines Purines are the larger of the two types of bases found in DNA Purines are the larger of the two types of bases found in DNA 

12. Pyrimidine Bases Cytosine, uracil and thymine are pyrimidines Cytosine, uracil and thymine are pyrimidines Mnemonic: Pyramids CUT Mnemonic: Pyramids CUT 

13. Because of their shapes, only some bases are compatible with each other Because of their shapes, only some bases are compatible with each other Purines always pair with pyramidines Purines always pair with pyramidines Adenine (A) always pairs with thymine (T) (in RNA, Adenine pairs with Uracil (U)) Adenine (A) always pairs with thymine (T) (in RNA, Adenine pairs with Uracil (U)) Guanine (G) with cytosine (C) Guanine (G) with cytosine (C) Nucleotide Bases Pairings

14. Counting Carbons

15. Nucleosides VS. Nucleotides A nucleoside is one of the four DNA bases covalently attached to a sugar A nucleoside is one of the four DNA bases covalently attached to a sugar Nucleosides differ from nucleotides in that they lack phosphate groups Nucleosides differ from nucleotides in that they lack phosphate groups A nucleotide is a nucleoside with one or more phosphate groups covalently attached to the sugar group A nucleotide is a nucleoside with one or more phosphate groups covalently attached to the sugar group  Step 1: Base Step 2: Nucleoside Step 3: Nucleotide

16. RNA RNA is made by copying DNA and is used to make proteins It is a SINGLE strand of nucleotides

17. DNA 1.Take two nucleic acid strands 2.Flip one of the strands 3.Line the strands together so that they bond 4.Twist them 5.Now you have DNA!

18. DNA: Double Helix Structure DNA has a double helix structure with two strands that are antiparallel so that nucleotides can form hydrogen bonds One Strand

19. H-Bonds But why is it important that the strands are H- bonded and not covalently bonded?

20. Why H-bonds? In order to replicate, the strands must separate to make new DNA strands (cannot be broken if the strands were covalently bound)

21. The sugar-phosphate backbones of the two polynucleotides are on the outside of the helix Pairs of nitrogenous bases, one from each strand, connect the polynucleotide chains with hydrogen bonds Most DNA molecules have thousands to millions of base pairs

22. Recap: What are the base-pair rules?  Adenine (A) always pairs with thymine (T) (in RNA, Adenine pairs with Uracil (U))  Guanine (G) with cytosine (C) With these base-pairing rules, if we know the sequence of bases on one strand, we know the sequence on the opposite strand The two strands are complementary Nucleotide Bases Pairings

23. DNA - Base pairing Adenine and Thymine always bind together Adenine and Thymine always bind together Guanine and Cytosine always bind together Guanine and Cytosine always bind together

24. Result: Double Helix Structure

25. An RNA molecule is single polynucleotide chain while DNA molecules have two polynucleotide strands that spiral around an imaginary axis to form a double helix The pentose joined to the nitrogen base is ribose in nucleotides of RNA and deoxyribose in DNA Nitrogen bases - thymine is replaced by uracil What’s the difference between RNA and DNA?

26. ATP ( adenosine triphosphate) ATP is a nucleotide that is used to provide energy in cells

27. NAD + and FAD These are nucleotide-containing molecules that function as electron carriers in a variety of cellular processes. NAD + - nicotinamide adenine dinucleotide FAD- flavin adenine dinucleotide

28. Home work Study the table on page 30 Do Question on page 31 Questions1-12 Macromolecules Quiz Next Thursday 15th for day 1 classes and Friday 16 th for day 2 classes