Lecture 3 Notes 1 26 15 All living organisms have 4 kinds of carbon based macromolecules proteins carbohydrates lipids nucleic acids Most macromolecules are POLYMERS which are long chains of smaller molecules called MONOMERS joined by covalent bonds Building blocks of life Amino acid protein Nucleotide nucleic acid Sugar monosaccharides polysaccharide can be linear or branched Phospholipid fatty acid membrane 2 tiered structure Important Functional Groups Hydroxyl Polar Hydrogen bonds w water to dissolve molecules Enables linkage to other molecules by condensation Aldehyde C O group is very reactive Important in building molecules and in energy releasing reactions Keto C O group is important in carbs and in energy reactions Carboxyl Acidic Ionizes in living tissues to form COO and H Gives up OH to enter into condensation reactions Amino Basic Accepts H in living tissues to form NH3 Gives up H to enter into condensation reactions How to make a polymer Condensation Water out energy in How to break a polymer Hydrolysis Water in energy out PROTEINS Proteins have a great diversity of function Enzymes catalytic proteins Defensive proteins antibodies Hormones control physiological processes Receptor proteins recieve and respond to molecular signals Structural proteins provide physical stability and movement Transport proteins carry substances within the organism Genetic regulatory proteins regulate when where and how much a gene is expresses Polymers of 20 different amino acids Linked by peptide bond Vary in length from a few amino acids to thousands Vary in composition of amino acids Titin is a huge protein 34 000 amino acids and adds flexibility to muscle fibers Thrytropin releasing hormone is a very small protein 3 amino acids and controls secretion of thyroid hormone Amino acids are grouped according to the properties of their side chain R groups Synthesis of Proteins Grow from N terminus C terminus each additional amino acid joined to C term of previous one Fold into specific reproducible shapes as a result of the amino acid composition and order Some proteins made from just one polypeptide others made from several Levels of Protein Structure Primary structure 1 the sequence of amino acids Determines secondary and tertiary structure how it folds Secondary structure 2 Regular repeated pattern in different regions of the amino acid chain that arise from hydrogen bonding between amino acids Alpha helix right handed coil resulting from hydrogen bonding Beta pleated sheet two or more polypeptide chain segments are aligned and held together by hydrogen bonds Tertiary structure 3 3D shape that arises from bending and folding interactions between R groups The outer surfaces present functional groups that can interact with other molecules Disulfide bridges The terminal where an SH group of cysteine can react with another cysteine side chain Different amino acid sequence leads to a different tertiary structure therefore a different function Quaternary structure 4 Association of two or more polypeptides to form the functional protein Proteins bind noncovalently with other cellular or extracellular molecules to perform their functions Binding is VERY specific Chaperones Proteins that help prevent inappropriate interactions Heat shock proteins HSPs The general class of stress induced chaperone proteins Denaturation A protein that gets heated causing the secondary and tertiary structures to be broken down Conditions that affect secondary and tertiary structure High temperature pH changes High concentrations of polar molecules Nonpolar substances Clicker Questions What is NOT true about the primary structure of a protein Cannot be branched Held together by covalent bonds Unique to that protein Determines the tertiary strutter Is the sequence of amino acids Which of the macromolecules polymerizes to form branched structures Carbohydrates