Chapter 4~ Carbon & The Molecular Diversity of Life Chapter 5~ The Structure & Function of Macromolecules Organic chemistry Carbon tetravalence Tetrahedron shape determine function Hydrocarbons Only carbon & hydrogen (petroleum; lipid tails) Covalent bonding; nonpolar High energy storage Isomers (same molecular formula, but different structure & properties) structural~differing covalent bonding arrangement geometric~differing spatial arrangement enantiomers~mirror images pharmacological industry (thalidomide) Figure 4.6 Three types of isomers Functional Groups, I Attachments that replace one or more of the hydrogens bonded to the carbon skeleton of the hydrocarbon Each has a unique property from one organic to another Hydroxyl Group H bonded to O; alcohols; polar (oxygen); solubility in water Carbonyl Group C double bond to O; At end of skeleton: aldehyde Otherwise: ketone Functional Groups, II Carboxyl Group O double bonded to C to hydroxyl; carboxylic acids; covalent bond between O and H; polar; dissociation, H ion Amino Group N to 2 H atoms; amines; acts as a base (+1) Functional Groups, III Sulfhydral Group sulfur bonded to H; thiols Phosphate Group phosphate ion; covalently attached by 1 of its O to the C skeleton; Polymers Covalent monomers Condensation reaction (dehydration reaction): One monomer provides a hydroxyl group while the other provides a hydrogen to form a water molecule Hydrolysis: bonds between monomers are broken by adding water (digestion) D:\ImageLibrary1-17\05- Macromolecules\ Macromolecules.mov Carbohydrates, I Monosaccharides CH 2 O formula; multiple hydroxyl (-OH) groups and 1 carbonyl (C=O) group: aldehyde (aldoses) sugar ketone sugar cellular respiration; raw material for amino acids and fatty acids Carbohydrates Functions: Energy source Provide building material (structural role) Contain carbon, hydrogen and oxygen in a 1:2:1 ratio Varieties: monosaccharides, disaccharides, and polysaccharides Carbohydrates, II Disaccharides glycosidic linkage (covalent bond) between 2 monosaccharides; covalent bond by dehydration reaction Sucrose (table sugar) most common disaccharide Figure 5.5 Examples of disaccharide synthesis Carbohydrates, III Polysaccharides Storage: Starch~ glucose monomers Plants: plastids Animals: glycogen Polysaccharides Structural: Cellulose~ most abundant organic compound; Chitin~exoskeletons; cell walls of fungi; surgical thread Lipids No polymers; glycerol and fatty acid Fats, phospholipids, steroids Hydrophobic; H bonds in water exclude fats Carboxyl group = fatty acid Non-polar C-H bonds in fatty acid tails Ester linkage: 3 fatty acids to 1 glycerol (dehydration formation) Triacyglycerol (triglyceride) Saturated vs. unsaturated fats; single vs. double bonds 15 Fatty acids are either unsaturated or saturated. Unsaturated - one or more double bonds between carbons GOOD type of fat Tend to be liquid at room temperature Example: plant oils Saturated - no double bonds between carbons Tend to be solid at room temperature BAD FAT Examples: butter, lard Triglycerides: Long-Term Energy Storage Phospholipids 2 fatty acids instead of 3 (phosphate group) Tails hydrophobic; heads hydrophilic Micelle (phospholipid droplet in water) Bilayer (double layer); cell membranes Steroids Lipids with 4 fused carbon rings Ex: cholesterol: cell membranes; precursor for other steroids (sex hormones) Proteins Importance: instrumental in nearly everything organisms do; 50% dry weight of cells; most structurally sophisticated molecules known Monomer: amino acids (there are 20) ~ carboxyl (-COOH) group, amino group (NH 2 ), H atom, variable group (R). Variable group characteristics: polar (hydrophilic), nonpolar (hydrophobic), acid or base Three-dimensional shape (conformation) Polypeptides (dehydration reaction): peptide bonds~ covalent bond; carboxyl group to amino group (polar) Proteins Proteins are polymers of amino acids linked together by peptide bonds. A peptide bond is a covalent bond between amino acids. Two or more amino acids joined together are called peptides. Long chains of amino acids joined together are called polypeptides. A protein is a polypeptide that has folded into a particular shape and has function. 21 Functions of Proteins Metabolism Most enzymes are proteins that act as catalysts to accelerate chemical reactions within cells. Support Keratin and collagen Transport Hemoglobin and membrane proteins Defense Antibodies Regulation Hormones are regulatory proteins that influence the metabolism of cells. Motion Muscle proteins and microtubules amino acid amino group Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Synthesis and Degradation of a Peptide dehydration reaction hydrolysis reaction water peptide bond dipeptide amino acid acidic groupamino group Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 24 Levels of Protein Structure Proteins cannot function properly unless they fold into their proper shape. When a protein loses it proper shape, it said to be denatured. Exposure of proteins to certain chemicals, a change in pH, or high temperature can disrupt protein structure. Proteins can have up to four levels of structure: Primary Secondary Tertiary Quaternary 25 Four Levels of Protein Structure Primary The sequence of amino acids Secondary Characterized by the presence of alpha helices and beta (pleated) sheets held in place with hydrogen bonds Tertiary Final overall three-dimensional shape of a polypeptide Stabilized by the presence of hydrophobic interactions, hydrogen bonding, ionic bonding, and covalent bonding Quaternary Consists of more than one polypeptide Primary Structure Conformation: Linear structure Molecular Biology: each type of protein has a unique primary structure of amino acids Ex: lysozyme Amino acid substitution: hemoglobin; sickle-cell anemia Secondary Structure Conformation: coils & folds (hydrogen bonds) Alpha Helix: coiling; keratin Pleated Sheet: parallel; silk Tertiary Structure Conformation: irregular contortions from R group bonding hydrophobic disulfide bridges hydrogen bonds ionic bonds Quaternary Structure Conformation: 2 or more polypeptide chains aggregated into 1 macromolecule collagen (connective tissue) hemoglobin Nucleic Acids, I Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) DNA->RNA->protein Polymers of nucleotides (polynucleotide): nitrogenous base pentose sugar phosphate group Nitrogenous bases: pyrimidines~cytosine, thymine, uracil purines~adenine, guanine Nucleic Acids Nucleic acids are polymers of nucleotides. Two varieties of nucleic acids: DNA (deoxyribonucleic acid) Genetic material that stores information for its own replication and for the sequence of amino acids in proteins. RNA (ribonucleic acid) Perform a wide range of functions within cells which include protein synthesis and regulation of gene expression 32 Structure of a Nucleotide Each nucleotide is composed of three parts: A phosphate group A pentose sugar A nitrogen-containing (nitrogenous) base There are five types of nucleotides found in nucleic acids. DNA contains adenine, guanine, cytosine, and thymine. RNA contains adenine, guanine, cytosine, and uracil. Nucleotides are joined together by a series of dehydration synthesis reactions to form a linear molecule called a strand. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. S C O P nitrogen- containing base pentose sugar 5' 4' 1' 2' 3' phosphate Nucleotides Figure 5.28 DNA RNA protein: a diagrammatic overview of information flow in a cell Figure 5.28 DNA RNA protein: a diagrammatic overview of information flow in a cell Nucleic Acids, II Pentoses: ribose (RNA) deoxyribose (DNA) nucleoside (base + sugar) Polynucleotide: phosphodiester linkages (covalent); phosphate + sugar Nucleic Acids, III Inheritance based on DNA replication Double helix (Watson & Crick ) H bonds~ between paired bases van der Waals~ between stacked bases A to T; C to G pairing Complementary 37 Structure of DNA and RNA The backbone of the nucleic acid strand is composed of alternating sugar-phosphate molecules. RNA is predominately a single-stranded molecule. DNA is a double-stranded molecule. DNA is composed of two strands held together by hydrogen bonds between the nitrogen- containing bases. The two strands twist around each other to form a double helix. Adenine hydrogen bonds with thymine Cytosine hydrogen bonds with guanine The bonding between the nucleotides in DNA is referred to as complementary base pairing. 38 A Special Nucleotide: ATP ATP (adenosine triphosphate) is composed of adenine, ribose, and three phosphates. ATP is a high-energy molecule due to the presence of the last two unstable phosphate bonds. Hydrolysis of the terminal phosphate bond yields: The molecule ADP (adenosine diphosphate) An inorganic phosphate Energy to do cellular work ATP is called the energy currency of the cell. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ATP N N N N + + P PP P P P N N N N ENERGY phosphatediphosphate ADP triphosphate ATPb. NH 2 H2OH2O adenosinetriphosphatec.a. adenosine c: Jennifer Loomis / Animals Animals / Earth Scenes