BIOL 141 Lecture Notes - Lecture 14: Protonation, Electronegativity, Zwitterion
Monday, September 18, 2017
BIOL 141
•Phenylalanine and valine would be able to polymerize via hydrophobic interactions,
but phenylalanine does not because its size is large."
•Structural proteins - give cell shape and mobility, cytoskeleton elements (actin,
tubular), extracellular matrix holds cells and tissues together"
•Cell surface proteins - receptors facilitate cell to cell communication"
•Channels and transporters regulate movement of molecules in/out of cell"
•Secreted proteins - peptide hormones coordinate body systems (homeostasis)"
•Antibodies defense against pathogens"
•Extracellular matrix made up of secreted proteins"
•Enzymes: protein catalyst, speed up the rate of chemical reactions"
•Enzymes are named according to their functions"
•Protonated - ionizable, deprotonated - ionic (charged) form"
•The charges on the functional groups help amino acids stay in solution where they
can interact with one another and with other solutes: they also alter amino acid
reactivity"
•Zwitterion - has both positive and negative charge"
•Cysteine is less polar compared to other polar side chains - electronegativity of
sulfur is lower"
•Two cysteine molecules bind by disulfide bond (which is a peptide bond?)"
•Glutamate (ionized) - glutamic acid (protonated)"
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