ASIM'S WEBWORLD View: Main School Main AP Biology Chapter Guides RELATED LINKS Review Questions and Answers		AP BIOLOGY: Chapter Three Outline INTRODUCTION Many Molecules Are Very Small Other Molecules Are Very Large Called macromolecules Four general types fig 3.1 THE BUILDING BLOCKS OF ORGANISMS The Chemistry of Carbon Organic molecules contain carbon Four electrons needed to fill outer orbital Has four equidistant binding sites Forms single, double and triple bonds with itself Four classes: carbohydrates, lipids, proteins, nucleic acids Have groups of atoms with definite chemical properties Are called functional groups fig 3.2 Most chemical reactions involve transfer of these groups Macromolecules Structural or informational function Many are polymers, repeating units bonded together Building Macromolecules Subunits joined by covalent bonds -OH removed from one subunit H+ removed from other subunit Dehydration synthesis (reaction) fig 3.3a Molecule of water removed as subunits are linked Requires input of energy to assemble Anabolic reactions build macromolecules from subunits Catalysis carried out by enzymes Hydrolysis reaction fig 3.3b Molecule of water added as subunits are broken apart Catabolic reactions disassemble molecules to subunits, energy released CARBOHYDRATES tbl 3.1 Sugars Are Simple Carbohydrates Contain C, H, O in 1:2:1 ratio Function in energy storage Important monosaccharides have six carbons and seven C-H bonds Empirical formula C6H12O6 or (CH2O)6 Are straight chains that form rings in water Primary six carbon sugar is glucose fig 3.4 Isomers fig 3.5 Have same empirical formula Atoms are arranged differently Glucose and fructose are structural isomers Glucose and galactose are stereoisomers Transport Disaccharides fig 3.6 Protects sugar from being metabolized during transport Are made of two monosaccharides linked together Maltose = glucose + glucose Sucrose = glucose + fructose Lactose = glucose + galactose Starches Are Chains of Sugars fig 3.7 Insoluble polymers called polysaccharides Starches are polysaccharides made from glucose Amylose is simplest form in plants Carbon 1 of glucose bonds to carbon 4 of next glucose Chains of maltose coil in water Pectins are branched polysaccharides in plants Called amylopectin when based on amylose Branches formed by cross-links, short chain length between branches Results in mesh of linked glucose units Glycogen is branched form in animals Long chain length Great number of branches Cellulose Is a Starch That Is Hard to Digest fig 3.8 Orientation of glucose subunits In starch all are on same side In cellulose subunits alternate sides Component of plant cell walls Same subunits as amylose Different bonds connect subunits Cannot be degraded by enzyme that breaks amylose Undigestible by most organisms, human dietary fiber Degraded by certain bacteria and protists Structural modification produces chitin fig 3.9 Present in insects and fungi Adds nitrogen group to glucose units LIPIDS tbl 3.1 Fats Are lipids that are insoluble due to nonpolar nature Cannot form hydrogen bonds like water can Fat molecules cluster together and exclude water Oils and waxes are other kinds of lipids Triglyceride = glycerol + three fatty acids fig 3.10 Fatty acids can be different from one another Saturated fatty acids fig 3.11 Internal carbons have maximum hydrogens Single bonds between carbons Present in hard animal fats Unsaturated fatty acids Internal carbons have fewer hydrogens Double bonds between many carbons Present in liquid plant oils Polyunsaturated fats have more than one double bond Humans and fats Over consumption of saturated fats raises cholesterol levels Natural unsaturated fats are healthier than saturated fats They are also healthier than artificially hydrogenated fats Efficient energy storage molecules Many C-H bonds, saturated have more than unsaturated 9 kcal per gram fat, 4 kcal per gram carbohydrate Conversion of consumed carbon molecules Glucose available for immediate use Disaccharides transported within organism Starch and fat storage reserves There Are Many Other Kinds of Lipids fig 3.12 Phospholipids comprise membranes Composed of polar head and nonpolar tail Form lipid bilayers fig 3.13 Polar head region faces outward Nonpolar tails face inward Steroids composed of four carbon rings Terpenes form various long-chain pigments Prostaglandins are modified fatty acids Composed of two nonpolar tails attached to ring Variety of biological functions PROTEINS tbl 3.1 Diverse Functions tbl 3.2 Enzymes are globular and catalyze biological reactions Fibrous proteins are structural fig 3.14 Peptides are short protein chemical messengers Amino Acids Are the Building Blocks of Protein Among first biological molecules to evolve Amino, carboxyl, hydrogen bonded to central carbon Identity conferred by variable R group Five classes fig 3.15 Nonpolar Polar, uncharged Ionizable Aromatic Special function Amino acids are linked together by peptide bonds fig 3.16 Proteins Are Chains of Amino Acids Proteins composed of one or more polypeptides Polypeptides are long chains of amino acids Each protein has a unique, defined amino acid sequence The Shape of Globular Proteins Globular protein chains are folded up into complex shapes Examine three dimensional structure with X-ray diffraction Myoglobin first one examined All internal amino acids are nonpolar Hydrophobic interactions shove nonpolar molecules inside Interactions result from hydrogen bonding Possess six structural levels fig 3.17 Primary, secondary, tertiary, quateranary, structures Motifs and domains Primary structure Specific amino acid sequence determined by gene's nucleotide sequence Permits great diversity of proteins Secondary structure Side groups, CO and NH groups of main chain form hydrogen bonds Two patterns of H bonding Linking of two amino acids along chain forms alpha helix Many parallel links across two chains forms beta sheet Motifs Sometimes called supersecondary structure ß a ß (beta-alpha-beta) creates fold or crease Beta-barrel is a beta sheet folded into a tube Helix-turn-helix binds to DNA double helix Tertiary structure Protein's final folded shape, positions motifs and side groups Spontaneous, driven by hydrophobic interactions with water Nonpolar chains in close proximity exhibit van der Waal's forces Allow very close fitting of nonpolar chains in protein interior Single amino acid change can significantly disrupt fit Domains Exon-encoded, structurally independent globular unit Several domains connected by single polypeptide chain Each domain may have different function Quaternary structure Combination of two or more polypeptide subunits Composes functional unit of a protein Denaturation Protein shape altered with changes in pH, temperature, ion concentration Protein becomes biologically inactive Enzymes function only within a narrow environmental range Proteins may return to natural shape fig 3.18 Large proteins rarely refold naturally May do so with help of protein chaperone cofactors NUCLEIC ACIDS tbl 3.1 Cellular Information Storage Devices, the Hereditary Material fig 3.19 Deoxyribonucleic acid = DNA, master molecule Ribonucleic acid = RNA, template copy Nucleotides Polymerize Forming Nucleic Acids Chemical components fig 3.19 Five-carbon ribose or deoxyribose sugar Phosphate group Organic nitrogen-containing base Phosphodiester bonds join sugars Nitrogen base attached to sugar and protrudes from chain Two kinds of organic bases fig 3.20 Purines: adenine (A), guanine (G) Pyrimidines: cytosine (C), thymine (T) (DNA), uracil (U) (RNA) Adenine also found in ATP, NAD and FAD fig 3.21 DNA Sequential nucleotides store hereditary information DNA forms double chains fig 3.22 Helix is a spiral staircase shape Two intertwined DNA molecules form a double helix Hydrogen bonds between bases hold chains together as duplex Base pairing is specific and complementary Adenine with thymine (DNA) or uracil (RNA) Guanine with cytosine (DNA and RNA) RNA Chemical differences between RNA and DNA RNA contains ribose sugar with hydroxyl at carbons 2 and 3 Uracil base in RNA, thymine in DNA Single stranded helix under most circumstances Which Came First, DNA or RNA DNA stores information for protein synthesis RNA is working copy of DNA master information DNA protected by not being actively used to make protein DNA evolved from RNA to protect the genetic information Flow of genetic information: DNA RNA protein