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Chapter 5

Chapter 5. The Structure and Function of Macromolecules. 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

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Chapter 5

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  1. Chapter 5 The Structure and Function of Macromolecules

  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. H H H C H H C H H H H H H H (a) Structural isomers H C C C C C H H C H C C H H H H H H H H H X X X C C C C (b) Geometric isomers X H H H CO2H CO2H C C (c) Enantiomers H H NH2 NH2 CH3 CH3 Figure 4.7 A-C Isomers • Isomers are molecules with the same molecular formula but different structures and properties • Three types of isomers are • Structural • Geometric • Enantiomers

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

  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

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

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

  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. 1 HO H 3 2 H HO Unlinked monomer Short polymer Dehydration removes a watermolecule, forming a new bond H2O 1 2 3 4 HO H Longer polymer (a) Dehydration reaction in the synthesis of a polymer Figure 5.2A The Synthesis and Breakdown of Polymers • Monomers form larger molecules by condensation reactions called dehydration synthesis

  11. 1 3 HO 4 2 H Hydrolysis adds a watermolecule, breaking a bond H2O 1 2 H HO 3 H HO (b) Hydrolysis of a polymer Figure 5.2B The Synthesis and Breakdown of Polymers • Polymers can disassemble by • Hydrolysis (addition of water molecules)

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

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

  16. Triose sugars(C3H6O3) Pentose sugars(C5H10O5) Hexose sugars(C6H12O6) H H H H O O O O C C C C H C OH H C OH H C OH H C OH H C OH H C OH HO C H HO C H Aldoses H H C OH H C OH HO C H H C OH H C OH H C OH Glyceraldehyde H C OH H C OH H Ribose H H Glucose Galactose H H H H C OH H C OH H C OH C O C O C O HO C H H C OH H C OH Ketoses H C OH H C OH H Dihydroxyacetone H C OH H C OH H C OH H Ribulose H Figure 5.3 Fructose • Examples of monosaccharides

  17. O H 1 C 6CH2OH 6CH2OH 2 CH2OH H C OH 5C H 5C O O 6 3 H O H H H H H 5 HO C H HOH H HOH 4 4C 1 C 1C 4C 4 1 OH H H H C OH O HO OH 3 2 OH OH 5 OH 2 C C 3 C 2C 3 OH H C H OH 6 H H OH OH H C OH H (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. Figure 5.4 • Monosaccharides • May be linear • Can form rings

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

  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.

  21. (a) 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. CH2OH CH2OH CH2OH CH2OH O O O O H H H H H H H H 1–4glycosidiclinkage HOH HOH HOH HOH 4 1 H H H H OH OH O H OH HO HO OH O H H H H OH OH OH OH H2O Glucose Maltose Glucose CH2OH CH2OH CH2OH CH2OH O O O O 1–2glycosidiclinkage H H H H H HOH HOH H 2 1 H OH H HO H HO H 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. (b) HO H O O HO CH2OH CH2OH OH H OH H H H OH OH H2O Glucose Sucrose Fructose 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).

  23. Polysaccharides • Polysaccharides • Are polymers of sugars • Serve many roles in organisms

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

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

  26. 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. Structural Polysaccharides • Cellulose • Is a polymer of glucose

  28. H O CH2OH C CH2OH OH OH H C H O O H H H H HO OH OH C H 4 4 1 H H HO OH HO OH H H C OH OH H OH H C H OH  glucose C  glucose H (a)  and  glucose ring structures CH2OH CH2OH CH2OH CH2OH O O O O OH OH OH OH 1 4 4 4 1 1 1 HO O O O O OH OH OH OH (b) Starch: 1– 4 linkage of  glucose monomers OH CH2OH OH CH2OH O O OH OH O O OH OH HO OH 4 O 1 O O CH2OH CH2OH OH OH (c) Cellulose: 1– 4 linkage of  glucose monomers Figure 5.7 A–C • Has different glycosidic linkages than starch

  29. About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. Cellulose microfibrils in a plant cell wall Microfibril Cell walls  0.5 m Plant cells OH OH CH2OH CH2OH O O O O OH OH OH OH O O O O O OH CH2OH OH CH2OH Cellulose molecules CH2OH OH CH2OH OH O O O O OH OH OH OH Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. O O O O O OH CH2OH OH CH2OH CH2OH CH2OH OH OH O O O O OH OH OH OH O O O A cellulose molecule is an unbranched  glucose polymer. O O OH CH2OH OH CH2OH Figure 5.8 • Glucose monomer • Is a major component of the tough walls that enclose plant cells

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

  31. CH2OH O OH H H OH H H H NH O C CH3 OH (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. (a) The structure of the chitin monomer. Figure 5.10 A–C • Chitin, another important structural polysaccharide • Is found in the exoskeleton of arthropods • Can be used as surgical thread

  32. 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

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

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

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

  36. 5’ end 5’C O 3’C O O 5’C O 3’C 3’ end OH Figure 5.26 The Structure of Nucleic Acids • Nucleic acids • Exist as polymers called polynucleotides (a) Polynucleotide, or nucleic acid

  37. Nucleoside Nitrogenous base O 5’C O O CH2 P O O Phosphate group 3’C Pentose sugar Figure 5.26 (b) Nucleotide • Each polynucleotide • Consists of monomers called nucleotides • Sugar + phosphate + nitrogen base

  38. Nitrogenous bases Pyrimidines NH2 O O C C CH3 C N CH HN C CH HN CH CH C CH C C CH CH N N O N O O H H H Cytosine C Uracil (in RNA) U Thymine (in DNA) T Uracil (in RNA) U Purines O NH2 C C N N C C NH N HC HC C CH C N N NH2 N N H H Adenine A Guanine G Pentose sugars 5” 5” OH OH HOCH2 HOCH2 O O H H H H 1’ 1’ 4’ 4’ H H H H 3’ 2’ 3’ 2’ H OH OH OH Deoxyribose (in DNA) Ribose (in RNA) Ribose (in RNA) Nucleotide Monomers • Nucleotide monomers • Are made up of nucleosides (sugar + base) and phosphate groups Figure 5.26 (c) Nucleoside components

  39. 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

  40. Gene • The sequence of bases along a nucleotide polymer • Is unique for each gene

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

  42. 3’ end 5’ end Sugar-phosphatebackbone Base pair (joined byhydrogen bonding) Old strands Nucleotideabout to be added to a new strand 3’ end A 5’ end Newstrands 3’ end 3’ end 5’ end Figure 5.27 • The DNA double helix • Consists of two antiparallel nucleotide strands

  43. 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)

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

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