Bios 208 1st Edition Exam 3 Study Guide I II III IV V VI VII I DNA Structure Components and Base Pairing Protein Structure Protein Functions and Levels of Structure Polymer Formation and Breakdown Enzymes Energy Use by Cells and Energy Units Free Energy ATP Structure and Function in Reactions DNA Structure Components and Base Pairing A The nitrogenous bases in DNA pair up and form hydrogen bonds adenine A always with thymine T and guanine G always with cytosine C B Called complementary base pairing C Complementary pairing can also occur between two RNA molecules or between parts of the same molecule D In RNA thymine is replaced by uracil U so A and U pair E The linear sequences of nucleotides in DNA molecules are passed from parents to offspring F Two closely related species are more similar in DNA than are more distantly related species G Molecular biology can be used to assess evolutionary kinship II Protein Structure Protein Functions and Levels of Structure A Protein Structure a A functional protein consists of one or more polypeptides precisely twisted folded and coiled into a unique shape b The coils and folds of secondary structure result from hydrogen bonds between repeating constituents of the polypeptide backbone c Typical secondary structures are a coil called an helix and a folded structure called a pleated sheet d The primary structure of a protein is its unique sequence of amino acids e Secondary structure found in most proteins consists of coils and folds in the polypeptide chain f Tertiary structure is determined by interactions among various side chains R groups g Quaternary structure results when a protein consists of multiple polypeptide chains h Order or sequence of AAs i Every protein has precise chain length and a specific AA at each position e g transthyretin has 127 AAs j Number of possible sequences 20n k 20 is the number of letters in the l Amino Acid alphabet n is the number of AAs in the chain m A protein s FUNCTION is dependent on its overall 3D STRUCTURE n Lysozyme an enzyme can kill bacteria by destroying their cell walls but only if the enzyme is in its native conformation o Tertiary structure is determined by interactions between R groups rather than interactions between backbone constituents p These interactions between R groups include hydrogen bonds ionic bonds hydrophobic interactions and van der Waals interactions q Strong covalent bonds called disulfide bridges may reinforce the protein s structure r Quaternary structure results when two or more polypeptide chains form one macromolecule s Collagen is a fibrous protein consisting of three polypeptides coiled like a rope t Hemoglobin is a globular protein consisting of four polypeptides two alpha and two beta chains u In addition to primary structure physical and chemical conditions can affect structure v Alterations in pH salt concentration temperature or other environmental factors can cause a protein to unravel w This loss of a protein s native structure is called denaturation x A denatured protein is biologically inactive y It is hard to predict a protein s structure from its primary structure z Most proteins probably go through several stages on their way to a stable structure aa Chaperonins are protein molecules that assist the proper folding of other proteins bb Diseases such as Alzheimer s Parkinson s and mad cow disease are associated with misfolded proteins B Protein Functions a Protein is a biologically functional molecule that consists of one or more polypeptides b Enzymes make break bonds as catalysts c Defense against disease antibodies d Amino acid storage e Transport across membranes f Hormones g Receptors h Cell motility i Structure and support C Levels of Structure a Enzymatic proteins 1 Function Selective acceleration of chemical reactions 2 Example Digestive enzymes catalyze the hydrolysis of bonds in food molecules b Defensive proteins 1 Function Protection against disease 2 Example Antibodies inactivate and help destroy viruses and bacteria c Storage proteins 1 Function Storage of amino acids 2 Examples Casein the protein of milk is the major source of amino acids for baby mammals Plants have storage proteins in their seeds Ovalbumin is the protein of egg white used as an amino acid source for the developing embryo d Transport proteins 1 Function Transport of substances 2 Examples Hemoglobin the iron containing protein of vertebrate blood transports oxygen from the lungs to other parts of the body Other proteins transport molecules across cell membranes e Hormonal proteins 1 Function Coordination of an organism s activities 2 Example Insulin a hormone secreted by the pancreas causes other tissues to take up glucose thus regulating blood sugar concentration f Receptor proteins 1 Function Response of cell to chemical stimuli 2 Example Receptors built into the membrane of a nerve cell detect signaling molecules released by other nerve cells g Contractile and motor proteins 1 Function Movement 2 Examples Motor proteins are responsible for the undulations of cilia and flagella Actin and myosin proteins are responsible for the contraction of muscles h Structural proteins 1 Function Support 2 Examples Keratin is the protein of hair horns feathers and other skin appendages Insects and spiders use silk fibers to make their cocoons and webs respectively Collagen and elastin proteins provide a fibrous framework in animal connective tissues III Polymer Formation and Breakdown A Amino Acid Polymers a Amino acids are linked by peptide bonds b A polypeptide is a polymer of amino acids c Polypeptides range in length from a few to more than a thousand monomers d Each polypeptide has a unique linear sequence of amino acids with a carboxyl end C terminus and an amino end N terminus e Polypeptide synthesis involves the carboxyl group of one AA with the amino group of another AA f Dehydration synthesis reaction g Peptide backbone has repeating pattern NCC NCC NCC h The first AA is at the amino end N terminus i Each new AA is added to the carboxyl end C terminus j R groups side chains stick out k The AA chain is a polypeptide B Nucleotide Polymers a Nucleotide polymers are linked together to build a polynucleotide b Adjacent nucleotides are joined by covalent bonds that form between the OH group on the 3 carbon of one nucleotide and the phosphate on the 5 carbon on the next c These links create a backbone of sugar phosphate units with nitrogenous bases as appendages d The sequence of bases