1.2 CARBOHYDRATES

1. 1.2 CARBOHYDRATES 1.1 WATER 1.3 LIPIDS MOLECULES OF LIFE 1.5 NUCLEIC ACIDS 1.4 PROTEINS

2. 1.5 NUCLEIC ACIDS

3. 1.5 Nucleic Acids (11/2 hours) Objectives : • Describe the structure of nucleotide as the basic composition of nucleic acid (DNA & RNA). • Describe the structure of DNA based on the Watson & Crick Model. • State the types and function of RNA. • State the differences of DNA & RNA.

4. Structure of nucleotide Differences of DNA & RNA Structure of DNA NUCLEIC ACIDS Types & function Of RNA mRNA, rRNA, tRNA

5. NUCLEIC ACIDS • Complex organic molecules • Polynucleotides (polymers of nucleotides) • 2 types DNA deoxyribonucleic acid RNA ribonucleic acid

6. Monomers / basic composition of nucleic acids Each nucleotide composed of: Phosphate group Pentose sugar Nitrogenous base STRUCTURE OF NUCLEOTIDE

7. STRUCTURE OF NUCLEOTIDE phosphate group (nitrogenous base)

8. STRUCTURE OF NUCLEOTIDE

9. Pentose sugar Ahydrogenatomattached to its 2nd carbon Ahydroxyl groupattached to its 2nd carbon Deoxyribose ( in DNA ) C5H10O4 Ribose ( in RNA ) C5H10O5

10. Ring structures for the 2 pentose sugars

11. STRUCTURE OF NUCLEOTIDE *In a nucleotide : - phosphate group is joined to the 5th C of pentose - nitrogenous base is joined to the 1st C of pentose

12. Nitrogenous base 2 groups 6-membered ring fused to a 5-membered ring 6-membered ring pyrimidine purine Cytosine Uracil (in RNA) Adenine Guanine Thymine (in DNA)

13. Nitrogenous base (a) Pyrimidines (Single ring) Cytosine (C) Thymine (T) in DNA Uracil (U) in RNA (b) Purines (Double ring) Adenine (A) Guanine (G)

14. Nucleotides are combined by condensation reaction forming a polynucleotide (DNA or RNA) FORMATION OF POLYNUCLEOTIDE

15. 2 nucleotides are joined by a phosphodiester bond - between a phosphate group (of a nucleotide) & the 3rd C in a pentose (of the other nucleotide) FORMATION OF POLYNUCLEOTIDE 5 4 1 3 2 Phosphodiester bond

16. Forming a backbone with repeating sugar-phosphate units Breakdown of polynucleotide may occur by hydrolysis FORMATION OF POLYNUCLEOTIDE

17. Organic bases Pentose sugars

18. Watson & Crick proposed the double helix model in 1953 for DNA 1 DNA molecule consists of 2 helical polynucleotide strands The pentose sugar: deoxyribose The nucleotides in each strand are joined by phosphodiester bonds STRUCTURE OF DNA

19. Contains 4 types of organic bases: - adenine (A) - guanine (G) - cytosine (C) - thymine (T) STRUCTURE OF DNA

20. Organic bases of each strand are paired in the interior of the helix The helix shape is maintained by H bonds between organic bases of opposite strands STRUCTURE OF DNA

21. Organic bases of each strand are paired in the interior of the helix The helix shape is maintained by H bonds between organic bases of opposite strands STRUCTURE OF DNA • The 2 strands must be complementary to each other • A must pair with T with 2 H bonds • G must pair with C with 3 H bonds • For a DNA, amount of A = T ; G = C

22. Hydrogen bonds Hydrogen bonds

23. The 2 strands must run in opposite directions (anti-parallel) ~1 strand runs 5’ 3’ while another runs 3’ 5’ STRUCTURE OF DNA

24. Sugar-phosphate backbone Sugar-phosphate backbone Base pairs 3’ OH 5’ 5’ OH 3’

25. The double helix The helix is “right-handed”, curving up to right. The two strands are held together by hydrogen bonds (dotted lines) between the nitrogenous bases, which are paired in the interior of the double helix.

26. DNA functions as the hereditary genetic material as it consists of nucleotides with certain sequence of organic bases IMPORTANCE OF DNA

27. Single stranded polynucleotide Pentose sugar: ribose Nitrogenous bases - Adenine (A) - Guanine (G) - Cytosine (C) - Uracil (U) RNA

28. RNA Organic base is uracil instead of thymine One nucleotide

29. 3 types of RNA : Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA) TYPES OF RNA

30. TYPES & FUNCTION OF RNA • i. mRNA • it carries the genetic code transcript (copiedfrom DNA) • carries it from the nucleus to the site of protein synthesisin thecytoplasm

31. Involvement of mRNA in protein synthesis

32. TYPES & FUNCTION OF RNA • rRNA • manufactured in the nucleolus • forms the ribosomal subunits (together with ribosomal proteins)

33. Involvement of rRNA in protein synthesis

34. TYPES & FUNCTION OF RNA • tRNA • smallest RNA molecules containing 75 - 80 nucleotides • different tRNAs to transfer (carry) thedifferent amino acidsto aribosomeduringprotein synthesis

35. tRNA

36. Involvement of tRNA in protein synthesis

37. Mainly functions in protein synthesis For certain virus, RNA may become the hereditary genetic material FUNCTIONS OF RNA

38. number of polynucleotide strands types of: pentose sugar nitrogenous bases location in cells chemical stability & existing basic form function molecular mass ratio of nitrogenous bases DIFFERENCES OF DNA & RNA

39. Differences between DNA and RNA

40. SEMESTER 1SESSION 2009/2010 Question Differentiate between RNA and DNA. [10 marks]

41. SESSION 1999/2000 Question • Elaborate on the structure of DNA according to Watson and Crick. [10 marks]

42. References : • Campbell, 8th edition • Solomon, 9th edition

43. Next Topic…. • 2.0 Cell Structure & Functions 2.1 Prokaryotic & Eukaryotic Cells 2.2 Plant & Animal Cells 2.3 Cell Membrane & Organelles Cell Structure & Functions 2.5 Cells are grouped into tissues 2.4 Cell Transport