MCB 2000 Exam 1

MCB 2000 Exam 1 Alanine (ala) nonpolar aliphatic Glycine (gly) nonpolar aliphatic Valine (val) nonpolar aliphatic branched chain Leucine (leu) nonpolar aliphatic branched chain Isoleucine (ile) nonpolar aliphatic branched chain Proline (pro) nonpolar aliphatic ring structure that is not aromatic Phenylalanine (phe) nonpolar aromatic permits absorption of UV light at 280 nm Tyrosine (tyr) polar and nonpolar properties -amphipathic uncharged aromatic OH group Tryptophan (trp) nonpolar aromatic permits absorption of UV light at 280 nm Serine (ser) polar uncharged OH group Threonine (thr) polar uncharge OH group Cysteine (cys) polar uncharged SH group -groups can become oxidized and form disulfide bonds to each other (S-S) Asparagine (asn) polar uncharged carboxamide group Methionine (met) nonpolar aliphatic thioether Glutamine (gln) polar uncharged carboxamide group Lysine (lys) polar charged positive Arginine (arg) polar charged positive Histidine (his) polar charged positive pKa 6, close to physiological can act as acid or base Aspartic acid (asp) polar charged negative Glutamic acid (glu) polar charged negative What makes water essential for life? -solvent -organizing principle -can be reactant or product in reaciton Common electronegative atoms in biological systems OxygenNitrogenSulfur Types of Noncovalent Interactions Hydrogen Bonding Electrostatic, Ionic interactions Van der Waals force Hyrdrophobic interactions Hydrogen bonds btwn electronegative atom (acceptor) and an H atom that is covalently bonded to another atom (donor) -dont last very long -weak association -bond is strongest at 180 degrees Importance of Hydrogen bonds -solvent properties of water -structure of proteins and nucleic acids Electrostatic, Ionic interactions Occur btwn atoms with a complete - charge and complete + charge -strength of interaction determine by distance and solvent Importance of electrostatic interactions protein-protein interactions DNA protein interactions Catalytic mechanisms Van der Waals forces charge fluctuations transiently produces + or - poles even in nonpolar molecules -weakest -present with snug fit btwn atoms -interactions in membranes - contributes to how permeable it is Hydrophobic interactions Nonpolar molecules that can not form H bonds -form spontaneously Hydrophobic interactions importance allow for an increase in entropy in water The hydrophobic effect Entropy driven association -structure function of proteins - hydrophobic amino acids on inside Importance of noncovalent interactions flexibility stability to large molecules essential to specificity 4 properties of all living organisms Chemical and energy transformation adaptation