AP Biology Proteins

AP Biology Proteins _______________

AP Biology Proteins  Most structurally & functionally diverse group  Function: involved in almost everything  (pepsin, DNA polymerase)  (keratin, collagen)  (hemoglobin, aquaporin)   (insulin & other hormones)   (antibodies)  (actin & myosin)  (bean seed proteins)

AP Biology Proteins  Structure  monomer =  20 different amino acids  polymer =  protein can be one or more polypeptide chains folded & bonded together   Rubisco hemoglobin growth hormones H2OH2O

AP Biology Amino acids  Structure    (acid)  (side chain)  variable group  different for each amino acid   like 20 different letters of an alphabet  can make many words (proteins) —N——N— H H C—OH || O R | —C— | H Oh, I get it! amino = NH 2 acid = COOH

AP Biology Effect of different R groups: Nonpolar amino acids Why are these nonpolar & hydrophobic? 

AP Biology Effect of different R groups: Polar amino acids  Why are these polar & hydrophillic?

AP Biology Ionizing in cellular waters H+ donors

AP Biology Ionizing in cellular waters H+ acceptors

AP Biology Sulfur containing amino acids  Form  covalent cross links betweens sulfhydryls  You wondered why perms smell like rotten eggs? H-S – S-H

AP Biology Building proteins  Peptide bonds   C–N bond peptide bond dehydration synthesis H2OH2O

AP Biology Building proteins  Polypeptide chains have direction  repeated sequence (N-C-C) is the _____________________  can only grow in one direction

AP Biology Protein structure & function hemoglobin   3-D structure  twisted, folded, coiled into unique shape collagen pepsin

AP Biology Primary (1°) structure    slight change in amino acid sequence can affect protein’s structure & its function  lysozyme: enzyme in tears & mucus that kills bacteria

AP Biology Sickle cell anemia Just 1 out of 146 amino acids!

AP Biology Secondary (2°) structure  “ ”  folding along short sections of polypeptide    weak bonds between R groups    -helix   -pleated sheet

AP Biology Secondary (2°) structure

AP Biology Tertiary (3°) structure  “ ”  interactions between distant amino acids   cytoplasm is water-based  nonpolar amino acids cluster away from water    covalent bonds between sulfurs in sulfhydryls (S–H)  anchors 3-D shape

AP Biology Quaternary (4°) structure   only then does polypeptide become functional protein  hydrophobic interactions collagen = skin & tendons hemoglobin

AP Biology 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°

AP Biology Protein denaturation   conditions that disrupt H bonds, ionic bonds, disulfide bridges     alter 2° & 3° structure  destroys functionality  In Biology, size doesn’t matter, SHAPE matters!