6 Nonpolar No charge associated with a molecule Electrons are evenly distributed creating no electrical field (charges cancel out each other)Symmetrical shapeIn amino acids (benzene ring/alkyl functional group)
13 Hydrophobic R groupsComposed mostly of carbon and hydrogen, and tend to be repelled from waterGlycine (Gly), alanine (Ala), valine (Val), leucine (Leu), isoleucine (Ile), proline (Pro), phenylalanine (Phe), methionine (Met), and tryptophan (Trp).
14 Polar amino acids Side chains that are not charged Serine (Ser), threonine (Thr), cysteine (Cys), asparagine (Asn), glutamine (Gln), and tyrosine (Tyr)
15 Basic amino acids Arginine (Arg), lysine (Lys), and histidine (His) Their side chains contain nitrogen and resemble ammonia, which is a base
16 Acidic amino acids Acidic R groups Aspartate (Asp) and glutamic acid or glutamate (Glu)
17 BondsAmino acids are linked together by peptide bonds
18 Primary (1°) structure Order of amino acids in chain amino acid sequence determined by gene (DNA)slight change in amino acid sequence can affect protein’s structure & its functioneven just one amino acid change can make all the difference!lysozyme: enzyme in tears & mucus that kills bacteria
19 Secondary (2°) structure “Local folding”folding along short sections of polypeptideinteractions between adjacent amino acidsH bondsweak bonds between R groupsforms sections of 3-D structure-helix-pleated sheet
20 Tertiary (3°) structure “Whole molecule folding”interactions between distant amino acidshydrophobic interactionscytoplasm is water-basednonpolar amino acids cluster away from waterH bonds & ionic bondsdisulfide bridgescovalent bonds between sulfurs in sulfhydryls (S–H)anchors 3-D shape
21 Quaternary (4°) structure More than one polypeptide chain bonded togetheronly then does polypeptide become functional proteinhydrophobic interactionshemoglobincollagen = skin & tendons
22 Protein structure (review) R groupshydrophobic interactionsdisulfide bridges(H & ionic bonds)3°multiple polypeptideshydrophobic interactions1°amino acid sequencepeptide bonds4°2°determined by DNAR groupsH bonds
23 Protein denaturation Unfolding a protein conditions that disrupt H bonds, ionic bonds, disulfide bridgestemperaturepHsalinityalter 2° & 3° structurealter 3-D shapedestroys functionalitysome proteins can return to their functional shape after denaturation, many cannot
24 EnzymesLock and key: The key (substrate) has a specific shape (arrangement of functional groups and other atoms) that allows it and no other key to fit into the lock (the enzyme).
25 EnzymesInduced fit: The substrate is distorted (atoms are shifted, bonds are stretched, and reactive groups are brought close together).Only molecules with the correct functional groups in the correct configurations are able to be induced to fit the active site of the enzyme.
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