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Chapter 5

Chapter 5. The Structure and Function of Macromolecules. Macromolecules. Are large molecules composed of smaller molecules Are complex in their structures. Protein. Macromolecules. Most macromolecules are polymers , built from monomers

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Chapter 5

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  1. Chapter 5 The Structure and Function of Macromolecules

  2. Macromolecules • Are large molecules composed of smaller molecules • Are complex in their structures Protein

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

  4. A polymer • Is a long molecule consisting of many similar building blocks called monomers • Specific monomers make up each macromolecule • Amino acids are the monomers for proteins • Monosaccharides make up carbohydrates • Glycerol and Fatty acids for Lipids • Nucleotides for Nucleic acids

  5. 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 or Condensation • Is an anabolic reaction (building up) Condensation of amino acids

  6. Dehydration Synthesis of Carbohydrates

  7. 1 3 HO 4 2 H Hydrolysis adds a watermolecule, breaking a bond H2O 1 2 H HO 3 H HO Figure 5.2B (b) Hydrolysis of a polymer The Synthesis and Breakdown of Polymers • Polymers can disassemble by • Hydrolysis (addition of water molecules) • Is a catabolic or breakdown reaction

  8. Hydrolysis of a Disaccharide

  9. 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 • How many words can be made using the English alphabet?

  10. Carbohydrates • C, H, O w/ a H:O ratio of 2:1 • Serve as fuel and building material • Sugars and their polymers (starch, cellulose, etc.) • Tend to end in “ase”

  11. Sugars • Monosaccharides • Are the simplest sugars • Most are: C6H12O6 • Can be used for fuel • Can be converted into other organic molecules • Can be combined into polymers • Glucose, Galactose, Fructose, Ribose…

  12. 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 Fructose Figure 5.3 • Examples of monosaccharides

  13. 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 3 2 O HO OH 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 Figure 5.4 (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. • Monosaccharides • May be linear • Can form rings

  14. Disaccharides • C12H22O11 • Consist of two monosaccharides • Are joined by a glycosidic linkage

  15. 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. (a) 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 OH H OH OH OH H2O Glucose Maltose Glucose CH2OH CH2OH CH2OH CH2OH O O O O H 1–2glycosidiclinkage H H H H H HOH HOH 2 1 OH H 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. HO H HO H (b) HO H O O HO CH2OH CH2OH OH H OH H H H OH OH H2O Glucose Sucrose Fructose Figure 5.5

  16. Polysaccharides • Polysaccharides • Are polymers of sugars • Serve many roles in organisms • Starch, glycogen, cellulose, chitin

  17. 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

  18. 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

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

  20. 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

  21. 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. Plant cells Cellulose molecules • Is a major component of the tough walls that enclose plant cells

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

  23. 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

  24. Lipids • Lipids are a diverse group of hydrophobic molecules • Lipids • Are the one class of large biological molecules that do not consist of polymers • Not considered a true macromolecules • Made up mostly of chains of hydrocarbons • Share the common trait of being hydrophobic • Fats, oils, waxes, phospholipids and steroids • Carbon, Hydrogen & Oxygen with H:O ratio >2:1 • Involved in long term energy storage

  25. Fats • Are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids • Vary in the length and number and locations of double bonds they contain

  26. Saturated fatty acids Have the maximum number of hydrogen atoms possible Have no double bonds Lard, butter, animal fat, palm oil, coconut oil, palm kernel oil Stearic acid Figure 5.12 (a) Saturated fat and fatty acid

  27. cis double bond causes bending Oleic acid Figure 5.12 (b) Unsaturated fat and fatty acid • Unsaturated fatty acids • Have one or more double bonds • Olive oil

  28. What to eat? • The following foods are high in monounsaturated fats: • peanut butter • olives • nuts – almonds, pecans, pistachios, cashews • avocado • seeds – sesame • oils – olive, sesame, peanut, canola • The following foods are high in polyunsaturated fats: • walnuts • seeds – pumpkin, sunflower • flaxseed • fish – salmon, tuna, mackerel • oils – safflower, soybean, corn

  29. Phospholipids • Have only two fatty acids • Have a phosphate group instead of a third fatty acid • Typical of a cell membrane

  30. + CH2 Choline N(CH3)3 CH2 O Phosphate Hydrophilic head – P O O O CH2 CH CH2 Glycerol O O C O C O Fatty acids Hydrophilic head Hydrophobic tails Hydrophobic tails (b) Space-filling model (c) Phospholipid symbol Figure 5.13 (a) Structural formula • Phospholipid structure • Consists of a hydrophilic “head” and hydrophobic “tails”

  31. WATER Hydrophilic head WATER Hydrophobic tail Figure 5.14 • The structure of phospholipids • Results in a bilayer arrangement found in cell membranes

  32. H3C CH3 CH3 CH3 CH3 HO Figure 5.15 Steroids • Steroids • Are lipids characterized by a carbon skeleton consisting of four fused rings • One steroid, cholesterol • Is found in cell membranes • Is a precursor for some hormones

  33. Proteins • Proteins have many structures, resulting in a wide range of functions • Building and regulatory functions • Proteins do most of the work in cells and act as enzymes • Proteins are made of monomers called amino acids • Made up of Carbon, Hydrogen, Oxygen, Nitrogen & sometimes Sulfur

  34. Table 5.1 • An overview of protein functions

  35. Substrate binds to enzyme. 1 Active site is available for a molecule of substrate, the reactant on which the enzyme acts. 2 2 Substrate (sucrose) Glucose Enzyme (sucrase) OH H2O Fructose H O 4 Products are released. 3 Substrate is converted to products. Figure 5.16 • Enzymes • Are a type of protein that acts as a catalyst, speeding up chemical reactions

  36. Polypeptides • Polypeptides • Are polymers (chains) of amino acids • A protein • Consists of one or more polypeptides

  37. Amino acids • Are organic molecules possessing both carboxyl and amino groups • Differ in their properties due to differing side chains, called R groups

  38. CH3 CH3 CH3 CH CH2 CH3 CH3 H CH3 H3C CH3 CH2 CH O O O O O H3N+ H3N+ H3N+ H3N+ C H3N+ C C C C C C C C C O– O– O– O– O– H H H H H Valine (Val) Leucine (Leu) Isoleucine (Ile) Glycine (Gly) Alanine (Ala) Nonpolar CH3 CH2 S H2C CH2 O NH CH2 H2N C C CH2 CH2 O– CH2 O O O H H3N+ H3N+ C C C C H3N+ C C O– O– O– H H H Phenylalanine (Phe) Proline (Pro) Methionine (Met) Tryptophan (Trp) Figure 5.17 Twenty Amino Acids • 20 different amino acids make up proteins

  39. OH NH2 O C NH2 O C OH SH CH2 Polar CH3 OH CH2 CH CH2 CH2 CH2 CH2 O O O O O O H3N+ H3N+ H3N+ H3N+ H3N+ H3N+ C C C C C C C C C C C C O– O– O– O– O– O– H H H H H H Glutamine (Gln) Tyrosine (Tyr) Asparagine (Asn) Cysteine (Cys) Serine (Ser) Threonine (Thr) Basic Acidic NH3+ NH2 NH+ O– O –O O NH2+ CH2 C C C Electrically charged NH CH2 CH2 CH2 CH2 CH2 O O H3N+ H3N+ CH2 CH2 C CH2 C C C O O– H3N+ O– CH2 C CH2 C H O H H3N+ O– C C CH2 H O O– H3N+ C C H O– H Lysine (Lys) Histidine (His) Arginine (Arg) Glutamic acid (Glu) Aspartic acid (Asp)

  40. Amino Acid Polymers • Amino acids • Are linked by peptide bonds

  41. Protein Conformation and Function • A protein’s specific conformation (shape) determines how it functions

  42. Amino acid subunits +H3NAmino end Pro Thr Gly Gly Thr Gly Glu Seu Lys Cys Pro Leu Met Val Lys Val Leu Asp Ala Arg Val Gly Ser Pro Ala Glu Lle Asp Thr Lys Ser Tyr Trp Lys Ala Leu Gly lle Ser Pro Phe His Glu His Ala Glu Val Thr Phe Val Ala Asn lle Thr Asp Ala Tyr Arg Ser Ala Arg Pro Gly Leu Leu Ser Pro Tyr Ser Tyr Ser Thr Thr Ala o Val c Val Glu – Lys o Thr Pro Asn Carboxyl end Figure 5.20 Four Levels of Protein Structure • Primary structure • Is the unique sequence of amino acids in a polypeptide

  43. H H H H H H O O O O O O O H H H H H H R R R R R R R C C C C C C C C C C C C C N N N N N N N N N N N N N C C C C C C C C C C C C C C R R R R R R H H H H H H H O O O O O O O H H H H H H H  pleated sheet H O H H Amino acidsubunits C C N N N C C C R H O H H H H H H N N N N N N  helix C C O C H H H C C C R R R R R H H C C C C C C O O O O H C R O C C O H C O N N H C C H R H R Figure 5.20 • Secondary structure • Is the folding or coiling of the polypeptide into a repeating configuration • Includes the  helix and the  pleated sheet

  44. Hydrophobic interactions and van der Waalsinteractions CH CH2 CH2 H3C CH3 OH Polypeptidebackbone H3C CH3 Hyrdogenbond CH O HO C CH2 CH2 S S CH2 Disulfide bridge O -O C CH2 CH2 NH3+ Ionic bond • Tertiary structure • Is the overall three-dimensional shape of a polypeptide • Results from interactions between amino acids and R groups

  45. Polypeptidechain Collagen  Chains Iron Heme  Chains Hemoglobin • Quaternary structure • Is the overall protein structure that results from the aggregation of two or more polypeptide subunits

  46. +H3N Amino end Amino acid subunits helix Review of Protein Structure

  47. Sickle-Cell Disease: A Simple Change in Primary Structure • Sickle-cell disease • Results from a single amino acid substitution in the protein hemoglobin

  48. Normal hemoglobin Sickle-cell hemoglobin Primary structure Exposed hydrophobic region Primary structure . . . . . . Glu His Leu Thr Pro Glul Val His Leu Pro Val Val Glu Thr 5 6 7 7 2 3 4 5 6 1 1 2 3 4 Secondaryand tertiarystructures Secondaryand tertiarystructures  subunit  subunit   Hemoglobin S   Quaternary structure Quaternary structure Hemoglobin A    Molecules interact with one another tocrystallize into a fiber, capacity to carry oxygen is greatly reduced.  Function Molecules donot associatewith oneanother, eachcarries oxygen. Function 10 m 10 m Red bloodcell shape Normal cells arefull of individualhemoglobinmolecules, eachcarrying oxygen Red bloodcell shape Figure 5.21 Fibers of abnormalhemoglobin deform cell into sickle shape.

  49. What Determines Protein Conformation? • Protein conformation depends on the physical and chemical conditions of the protein’s environment • Temperature, pH, [salt], etc. influence protein structure

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