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Chapter 4

Chapter 4. Carbon and the Molecular Diversity of Life. Figure 4.1. Carbon Chemistry. Carbon is the Backbone of Biological Molecules (macromolecules) All living organisms Are made up of chemicals based mostly on the element carbon. Carbon Chemistry.

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Chapter 4

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  1. Chapter 4 Carbon and the Molecular Diversity of Life

  2. Figure 4.1 Carbon Chemistry • Carbon is the Backbone of Biological Molecules (macromolecules) • All living organisms Are made up of chemicals based mostly on the element carbon

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

  4. Ball-and-Stick Model Name and Comments Space-Filling Model Molecular Formula Structural Formula H (a) Methane CH4 C H H H H H (b) Ethane C2H6 C H C H H H H H (c) Ethene (ethylene) C C C2H4 H H Figure 4.3 A-C • The bonding versatility of carbon allows it to form many diverse molecules, including carbon skeletons

  5. Carbon (valence = 4) Nitrogen (valence = 3) Hydrogen (valence = 1) Oxygen (valence = 2) O H N C Figure 4.4 • The electron configuration of carbon gives it covalent compatibility with many different elements

  6. H H C C C C H H C H H H H H H C H H H H H H H H H H H H C C C C C C C H H H H H H H H H H H H (a) Length H Ethane Propane H H H H H H H H H H H C C C C C C C C H H H H (b) Branching Butane isobutane H H H H C H (c) Double bonds H H C C C H H C C H H C C 1-Butene 2-Butene H H C C C (d) Rings Figure 4.5 A-D Cyclohexane Benzene • Carbon may bond to itself forming carbon chains • Carbon chains form the skeletons of most organic molecules • Carbon chains vary in length and shape

  7. Fat droplets (stained red) 100 µm (b) Mammalian adipose cells (a) A fat molecule Figure 4.6 A, B Hydrocarbons • Hydrocarbons are molecules consisting of only carbon and hydrogen • Hydrocarbons Are found within many of a cell’s organic molecules

  8. OH CH3 Estradiol HO Female lion OH CH3 CH3 O Testosterone Male lion Figure 4.9 Functional Groups • Functional groups are the parts of molecules involved in chemical reactions • They Are the chemically reactive groups of atoms within an organic molecule • Give organic molecules distinctive chemical properties

  9. Six functional groups are important in the chemistry of life • Hydroxyl • Carbonyl • Carboxyl • Amino • Sulfhydryl • Phosphate

  10. FUNCTIONAL GROUP HYDROXYL CARBONYL CARBOXYL O O OH C C OH (may be written HO ) In a hydroxyl group (—OH), a hydrogen atom is bonded to an oxygen atom, which in turn is bonded to the carbon skeleton of the organic molecule. (Do not confuse this functional group with the hydroxide ion, OH–.) STRUCTURE The carbonyl group( CO) consists of a carbon atom joined to an oxygen atom by a double bond. When an oxygen atom is double-bonded to a carbon atom that is also bonded to a hydroxyl group, the entire assembly of atoms is called a carboxyl group (—COOH).  Figure 4.10 Some important functional groups of organic compounds

  11. Ketones if the carbonyl group is within a carbon skeleton Aldehydes if the carbonyl group is at the end of the carbon skeleton NAME OF COMPOUNDS Alcohols (their specific names usually end in -ol) Carboxylic acids, or organic acids EXAMPLE H H H H O O C C H OH C C H C H C H OH H H H H C Ethanol, the alcohol present in alcoholic beverages H H Acetic acid, which gives vinegar its sour tatste Acetone, the simplest ketone H H O H C C C H H H Propanal, an aldehyde Figure 4.10 Some important functional groups of organic compounds

  12. AMINO SULFHYDRYL PHOSPHATE O H SH N P OH O (may be written HS ) H OH In a phosphate group, a phosphorus atom is bonded to four oxygen atoms; one oxygen is bonded to the carbon skeleton; two oxygens carry negative charges; abbreviated P . The phosphate group (—OPO32–) is an ionized form of a phosphoric acid group (—OPO3H2; note the two hydrogens). The amino group (—NH2) consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton. The sulfhydryl group consists of a sulfur atom bonded to an atom of hydrogen; resembles a hydroxyl group in shape. Figure 4.10 • Some important functional groups of organic compounds

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

  14. Macromolecules • Most macromolecules are polymers, built from monomers • Four classes of life’s organic molecules are polymers • Carbohydrates (include sugars, starches etc) • Proteins • Nucleic acids • Lipids (fats)

  15. 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

  16. 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

  17. 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)

  18. 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

  19. Carbohydrates • Serve as fuel and building material • Include both sugars and their polymers (starch, cellulose, etc.)

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

  21. 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

  22. 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

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

  24. (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

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

  26. 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

  27. 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

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

  29. 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

  30. 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

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

  32. 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

  33. Lipids • Lipids are a diverse group of hydrophobic molecules • Lipids • Are the one class of large biological molecules that do not consist of polymers • Share the common trait of being hydrophobic

  34. 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

  35. 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

  36. Fats • Are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids

  37. Fats • Vary in the length and number and locations of double bonds they contain

  38. Saturated fatty acids Have the maximum number of hydrogen atoms possible Have no double bonds Stearic acid Figure 5.12 (a) Saturated fat and fatty acid

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

  40. Phospholipids • Have only two fatty acids • Have a phosphate group instead of a third fatty acid

  41. + 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 (c) Phospholipid symbol (b) Space-filling model Figure 5.13 (a) Structural formula • Phospholipid structure • Consists of a hydrophilic “head” and hydrophobic “tails”

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

  43. Steroids • Steroids • Are lipids characterized by a carbon skeleton consisting of four fused rings

  44. H3C CH3 CH3 CH3 CH3 HO Figure 5.15 • One steroid, cholesterol • Is found in cell membranes • Is a precursor for some hormones

  45. Proteins • Proteins have many structures, resulting in a wide range of functions • Proteins do most of the work in cells and act as enzymes • Proteins are made of monomers called amino acids

  46. Table 5.1 • An overview of protein functions

  47. 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

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

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

  50. 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

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