Nonpolar No charge associated with a molecule Electrons are evenly distributed creating no electrical field (charges cancel out each other) Symmetrical shape In amino acids (benzene ring/alkyl functional group)
Hydrophobic R groups Composed mostly of carbon and hydrogen, and tend to be repelled from water Glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), isoleucine (Ile), proline (Pro), phenylalanine (Phe), methionine (Met), and tryptophan (Trp).
Polar amino acids Side chains that are not charged Serine (Ser), threonine (Thr), cysteine (Cys), asparagine (Asn), glutamine (Gln), and tyrosine (Tyr)
Basic amino acids Arginine (Arg), lysine (Lys), and histidine (His) Their side chains contain nitrogen and resemble ammonia, which is a base
Acidic amino acids Acidic R groups Aspartate (Asp) and glutamic acid or glutamate (Glu)
Bonds Amino acids are linked together by peptide bonds
Primary (1°) structure Order of amino acids in chain amino acid sequence determined by gene (DNA) slight change in amino acid sequence can affect proteins structure & its function even just one amino acid change can make all the difference! lysozyme: enzyme in tears & mucus that kills bacteria
Secondary (2°) structure Local folding folding along short sections of polypeptide interactions between adjacent amino acids H bonds weak bonds between R groups forms sections of 3-D structure -helix -pleated sheet
Tertiary (3°) structure Whole molecule folding interactions between distant amino acids hydrophobic interactions cytoplasm is water-based nonpolar amino acids cluster away from water H bonds & ionic bonds disulfide bridges covalent bonds between sulfurs in sulfhydryls (S–H) anchors 3-D shape
Quaternary (4°) structure More than one polypeptide chain bonded together only then does polypeptide become functional protein hydrophobic interactions collagen = skin & tendons hemoglobin
Protein structure (review) amino acid sequence peptide bonds 1° determined by DNA R groups H bonds R groups hydrophobic interactions disulfide bridges (H & ionic bonds) 3° multiple polypeptides hydrophobic interactions 4° 2°
Protein denaturation Unfolding a protein conditions that disrupt H bonds, ionic bonds, disulfide bridges temperature pH salinity alter 2° & 3° structure alter 3-D shape destroys functionality some proteins can return to their functional shape after denaturation, many cannot
Enzymes Lock 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).
Enzymes Induced 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.