1. 1 Chapter 5 The Structure and Function of Macromolecules

2. 2 Carbon Chemistry Organic chemistry is the study of carbon compounds Carbon atoms can form diverse molecules by bonding to four other atoms Carbon compounds range from simple molecules to complex ones Carbon has four valence electrons and may form single, double, triple, or quadruple bonds

3. 3 Isomers Isomers are molecules with the same molecular formula but different structures and properties Three types of isomers are –Structural –Geometric –Enantiomers H H HH H H H H HH H H H HH H H H H H H H H H H H H H CO 2 H CH 3 NH 2 C CO 2 H H CH 3 NH 2 XX X X C CCCC C C C C C C C C C C (a) Structural isomers (b) Geometric isomers (c) Enantiomers H Figure 4.7 A-C

4. 4 Enantiomers Are important in the pharmaceutical industry L-Dopa (effective against Parkinson’s disease) D-Dopa (biologically inactive) Figure 4.8

5. Pararhodopsin (inactive) and rhodopsin (active) – made by rods in the retina Conversion between the two is done by an enzyme complex that requires Vitamin A 5

6. 6 The Molecules of Life Overview: –Another level in the hierarchy of biological organization is reached when small organic molecules are joined together –Atom ---> molecule ---  compound

7. 7 Macromolecules –Are large molecules composed of smaller molecules –Are complex in their structures Figure 5.1

8. 8 Macromolecules Most macromolecules are polymers, built from monomers Four classes of life’s organic molecules are polymers –Carbohydrates –Proteins –Nucleic acids –Lipids

9. 9 A polymer –Is a long molecule consisting of many similar building blocks called monomers –Specific monomers make up each macromolecule –E.g. amino acids are the monomers for proteins

10. 10 The Synthesis and Breakdown of Polymers Monomers form larger molecules by condensation reactions called dehydration synthesis (a) Dehydration reaction in the synthesis of a polymer HOH 1 2 3 H 1 23 4 H H2OH2O Short polymer Unlinked monomer Longer polymer Dehydration removes a water molecule, forming a new bond Figure 5.2A

11. 11 The Synthesis and Breakdown of Polymers Polymers can disassemble by –Hydrolysis (addition of water molecules) (b) Hydrolysis of a polymer HO 1 2 3 H H 1 2 3 4 H2OH2O H Hydrolysis adds a water molecule, breaking a bond Figure 5.2B

12. 12 Although organisms share the same limited number of monomer types, each organism is unique based on the arrangement of monomers into polymers An immense variety of polymers can be built from a small set of monomers

13. 13 Carbohydrates Serve as fuel and building material Include both sugars and their polymers (starch, cellulose, etc.) 1:2:1 ratio of C:H:O

14. 14 Sugars Monosaccharides –Are the simplest sugars –Can be used for fuel –Can be converted into other organic molecules –Can be combined into polymers

15. 15 Types of Monosaccharides Triose – formula ______ ex. glyceraldehyde and dihydroxyacetoneglyceraldehydedihydroxyacetone Tetrose – formula Pentose- formula ____ Ex. ribose Hexose – formula ____ ex. glucose, dextrose, fructose, galactose Heptose – formula ____

16. 16 Examples of monosaccharides Triose sugars (C 3 H 6 O 3 ) Pentose sugars (C 5 H 10 O 5 ) Hexose sugars (C 6 H 12 O 6 ) H C OH HO C H H C OH HO C H H C OH C O H C OH HO C H H C OH C O H H H HHH H H HHH H H H C CCC O O O O Aldoses Glyceraldehyde Ribose Glucose Galactose Dihydroxyacetone Ribulose Ketoses Fructose Figure 5.3

17. 17 Monosaccharides –May be linear –Can form rings H H C OH HO C H H C OH H C O C H 1 2 3 4 5 6 H OH 4C4C 6 CH 2 OH 5C5C H OH C H OH H 2 C 1C1C H O H OH 4C4C 5C5C 3 C H H OH OH H 2C2C 1 C OH H CH 2 OH H H OH HO H OH H 5 3 2 4 (a) Linear and ring forms. Chemical equilibrium between the linear and ring structures greatly favors the formation of rings. To form the glucose ring, carbon 1 bonds to the oxygen attached to carbon 5. OH 3 O H O O 6 1 Figure 5.4

18. 18 What is the difference between alpha and beta glucose? Top of page 73 in your book

19. 19 Disaccharides –Consist of two monosaccharides –Are joined by a bond called a glycosidic linkage –These bonds are numbered. The numbers come from what two carbons the bond forms between

20. Example: In sucrose, glucose and fructose are bonded together by a 1-2 glycosidic linkage. The 1 C on the glucose molecule and the 2 C on the fructose molecule. Extremely important that you know the numbers. 20

21. 21 Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide. Dehydration reaction in the synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose. Notice that fructose, though a hexose like glucose, forms a five-sided ring. (a) (b) H HO H H OH H OH O H CH 2 OH H HOHO H HOHHOH H OHOH O H OHOH H O H H OH H OH O H CH 2 OH H H2OH2O H2OH2O H H O H HO H OH O H CH 2 OH HO OH H CH 2 OH HOHHOH H H HO OH H CH 2 OH HOHHOH H O O H OH H CH 2 OH HOHHOH H O H OH CH 2 OH H HO O CH 2 OH H H OH O O 1 2 1 4 1– 4 glycosidic linkage 1–2 glycosidic linkage Glucose Fructose Maltose Sucrose OH H H Figure 5.5

22. Maltose is glu + glu with a 1 – 4 glycosidic linkage. Maltose is the sugar in beer, found in germinating grain and some in corn syrup. If you turn the second glucose molecule around so that the bond is a 1 – 1 glycosidic linkage, you don’t get maltose. You get trehalose which is the sugar found in insects’ blood (also used in some hair care products). 22

23. Oligosaccharides – between 3 and 15 monomers important in cell membrane structure 23

24. 24 Polysaccharides –Are polymers of sugars –Serve many roles in organisms

25. 25 Storage Polysaccharides Starch –Is a polymer consisting entirely of glucose monomers –Is the major storage form of glucose in plants Chloroplast Starch Amylose Amylopectin 1  m (a) Starch: a plant polysaccharide Figure 5.6

26. 26 Glycogen –Consists of glucose monomers –Is the major storage form of glucose in animals in liver Mitochondria Giycogen granules 0.5  m (b) Glycogen: an animal polysaccharide Glycogen Figure 5.6

27. Glucagon – made by the alpha cells in the islet of Langerhans in the pancreas breaks glycogen down and makes it glucose again (glycogenolysis) Insulin is made by beta cells of the islet of Langerhans They are antagonistic hormones. 27

28. 28 Structural Polysaccharides Cellulose –Is a polymer of glucose

29. 29 –Has different glycosidic linkages than starch (c) Cellulose: 1– 4 linkage of  glucose monomers H O O CH 2 O H H OHOH H H OHOH OHOH H H HOHO 4 C C C C C C H H H HOHO OHOH H OHOH OHOH OHOH H O H H H OHOH OHOH H H HOHO 4 OHOH O OHOH OHOH HOHO 4 1 O O OHOH OHOH O O OHOH OHOH O OHOH OHOH O O O OHOH OHOH HOHO 4 O 1 OHOH O OHOH OHOH O O OHOH O OHOH O OHOH OHOH (a)  and  glucose ring structures (b) Starch: 1– 4 linkage of  glucose monomers 1  glucose  glucose CH 2 O H 1 4 4 1 1 Figure 5.7 A–C

30. 30 Plant cells 0.5  m Cell walls Cellulose microfibrils in a plant cell wall  Microfibril CH 2 OH OH OHOH O O O CH 2 OH O O OH O CH 2 OH OH O O CH 2 OH O O OHOH O O OHOH O O OH CH 2 OHOH O O CH 2 OH OH O CH 2 OH O O OHCH 2 OH OH  Glucose monomer O O O O O O Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. A cellulose molecule is an unbranched  glucose polymer. OH O O Cellulose molecules Figure 5.8 –Is a major component of the tough walls that enclose plant cells

31. 31 Cellulose is difficult to digest –Cows have microbes in their stomachs to facilitate this process Figure 5.9

32. 32 Chitin, another important structural polysaccharide –Is found in the exoskeleton of arthropods –Can be used as surgical thread (a) The structure of the chitin monomer. O CH 2 O H OH H H H NH C CH 3 O H H (b) Chitin forms the exoskeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emerging in adult form. (c) Chitin is used to make a strong and flexible surgical thread that decomposes after the wound or incision heals. OH Figure 5.10 A–C

33. 33 Nucleic Acids Nucleic acids store and transmit hereditary information Genes –Are the units of inheritance –Program the amino acid sequence of polypeptides –Are made of nucleotide sequences on DNA

34. 34 The Roles of Nucleic Acids There are two types of nucleic acids –Deoxyribonucleic acid (DNA) –Ribonucleic acid (RNA)

35. 35 Deoxyribonucleic Acid DNA –Stores information for the synthesis of specific proteins –Found in the nucleus of cells

36. 36 DNA Functions –Directs RNA synthesis (transcription) –Directs protein synthesis through RNA (translation) 1 2 3 Synthesis of mRNA in the nucleus Movement of mRNA into cytoplasm via nuclear pore Synthesis of protein NUCLEUS CYTOPLASM DNA mRNA Ribosome Amino acids Polypeptide mRNA Figure 5.25

37. 37 The Structure of Nucleic Acids Nucleic acids –Exist as polymers called polynucleotides (a) Polynucleotide, or nucleic acid 3’C 5’ end 5’C 3’C 5’C 3’ end OH Figure 5.26 O O O O

38. 38 Each polynucleotide –Consists of monomers called nucleotides –Sugar + phosphate + nitrogen base Nitrogenous base Nucleoside O O OO OO P CH 2 5’C 3’C Phosphate group Pentose sugar (b) Nucleotide Figure 5.26 O

39. 39 Nucleotide Monomers Nucleotide monomers –Are made up of nucleosides (sugar + base) and phosphate groups Two types of bases: purines (A and G) and pyrimidines (C, T and U) (c) Nucleoside components Figure 5.26 CH Uracil (in RNA) U Ribose (in RNA) Nitrogenous bases Pyrimidines C N N C O H NH 2 CH O C N H HN C O C CH 3 N HN C C H O O Cytosine C Thymine (in DNA) T N HC N C C N C CH N NH 2 O N HC N H H C C N NH C NH 2 Adenine A Guanine G Purines O HOCH 2 H H H OH H O HOCH 2 H H H OH H Pentose sugars Deoxyribose (in DNA) Ribose (in RNA) OH CH Uracil (in RNA) U 4’ 5”5” 3’ OH H 2’ 1’ 5”5” 4’ 3’ 2’ 1’

40. 40 Nucleotide Polymers Nucleotide polymers – Are made up of nucleotides linked by the–OH group on the 3´ carbon of one nucleotide and the phosphate on the 5´ carbon on the next

41. 41 Gene The sequence of bases along a nucleotide polymer –Is unique for each gene

42. 42 The DNA Double Helix Cellular DNA molecules –Have two polynucleotides that spiral around an imaginary axis –Form a double helix

43. 43 The DNA double helix –Consists of two antiparallel nucleotide strands 3’ end Sugar-phosphate backbone Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a new strand A 3’ end 5’ end New strands 3’ end 5’ end Figure 5.27

44. 44 A,T,C,G The nitrogenous bases in DNA –Form hydrogen bonds in a complementary fashion (A with T only, and C with G only in DNA A with U in RNA)

45. 45 DNA and Proteins as Tape Measures of Evolution Molecular comparisons –Help biologists sort out the evolutionary connections among species