Transcript R–groups
LEVELS OF PROTEIN STRUCTURE A. Primary Structure—the unique sequence of amino acids, type sequence and number; determines the other three structures It is held together by peptide bonds between the carboxyl group of one amino acid with the amino group of another amino acid B. Secondary Structure― regular repeated coiling and folding of the polypeptide caused by H–bonds between atoms in the polypeptide backbone (a hydrogen on a nitrogen and a double–bonded oxygen atom) see Fig. 5.20 p. 76 a. alpha helix― a delicate coil held together by hydrogen bonding between every fourth peptide bond b. Beta pleated sheet― where regions of the chain lie parallel to each other LEVELS OF PROTEIN STRUCTURE C. Tertiary Structure―the irregular contortions in the polypeptide chain caused by bonding between atoms in the side chains (R–groups) a. hydrogen bonds between atoms in R–groups b. hydrophobic interactions― the congregating of nonpolar R– groups in the core of the protein away from water c. hydrophilic interactions― the twisting of polar R–groups toward water d. ionic bonds between positively and negatively charged R– groups of some amino acids e. disulfide bridges― covalent bonds between two cysteine amino acids with sulfhydryl groups are brought close enough together by the folding of the protein D. Quaternary Structure― when two or more polypeptide chains are joined together by bonds or interactions of their R–groups. Same as a–e above. THE STRUCTURE AND FUNCTION OF MACROMOLECULES Linus Pauling determined the alpha helix structure of a protein Alias-PGAL or G3P Ribulose as in biphosphate 6 5 4 1 3 2 1 5 2 3 4 6 curved chain that forms a coil curved chain that forms a coil with many branches curved It has more branches than amylopectin All these can form H-bonds with other cellulose molecules alpha-glucose starch beta-glucose cellulose STARCH 1. alpha glucose CELLULOSE 1. beta glucose 2. 14 bonds easily 2. 14 bonds only broken by the broken by vertebrate enzymes of a few bacteria enzymes protozoans and fungi 3. forms helix w/ OH's 3. forms straight molecule inside making it w/ OH's sticking out slightly soluble above and below 4. no H-bonds between chains 5. energy storage 4. forms H-bonds between chains 5. structural uses Chitin-structural polysaccharide found in arthropod exoskeletons and fungus cell walls Monomers of beta glucose with a nitrogen containing group on the #2 carbon Chitin-structural polysaccharide found in arthropod exoskeletons and fungus cell walls Triacylglycerol—stores twice as much energy per gram as carbohydrates; also used structurally as cushions around vital organs and insulation against heat loss waxes Glycolipid-a chain of sugars attached to the third carbon of a glycerol-- gives it a polar but not charged head; found in cell membranes; it has a polar but not charged head and two nonpolar tails so it sits a little deeper in the membrane; It is used for adhesion and identification by lymphocytes PROTEINS POLYMERS OF AMINO ACIDS PROTEINS POLYMERS OF AMINO ACIDS alanine cysteine Dipeptide Hydrogen bonds alpha helix beta pleated sheet Secondary structures 3 alpha helix into a quartenary Microtubules-a fibrous or tubular protein composed of many globular dimers LEVELS OF PROTEIN STRUCTURE A. Primary Structure—the unique sequence of amino acids, type sequence and number; determines the other three structures It is held together by peptide bonds between the carboxyl group of one amino acid with the amino group of another amino acid B. Secondary Structure― regular repeated coiling and folding of the polypeptide caused by H–bonds between atoms in the polypeptide backbone (a hydrogen on a nitrogen and a double–bonded oxygen atom) see Fig. 5.20 p. 76 a. alpha helix― a delicate coil held together by hydrogen bonding between every fourth peptide bond b. Beta pleated sheet― where regions of the chain lie parallel to each other LEVELS OF PROTEIN STRUCTURE C. Tertiary Structure―the irregular contortions in the polypeptide chain caused by bonding between atoms in the side chains (R–groups) a. hydrogen bonds between atoms in R–groups b. hydrophobic interactions― the congregating of nonpolar R– groups in the core of the protein away from water c. hydrophilic interactions― the twisting of polar R–groups toward water d. ionic bonds between positively and negatively charged R– groups of some amino acids e. disulfide bridges― covalent bonds between two cysteine amino acids with sulfhydryl groups are brought close enough together by the folding of the protein D. Quaternary Structure― when two or more polypeptide chains are joined together by bonds or interactions of their R–groups. Same as a–e above.