Proteins AP Biology Proteins Multipurpose molecules AP Biology

Proteins AP Biology Proteins Multipurpose molecules AP Biology

Proteins AP Biology Proteins Multipurpose molecules AP Biology 2008-2009 Proteins Most structurally & functionally diverse group Function: involved in almost everything

AP Biology enzymes (pepsin, DNA polymerase) structure (keratin, collagen) carriers & transport (hemoglobin, aquaporin) cell communication

signals (insulin & other hormones) receptors defense (antibodies) movement (actin & myosin) storage (bean seed proteins) Proteins Structure H2O monomer = amino acids 20 different amino acids

polymer = polypeptide protein can be one or more polypeptide chains folded & bonded together large & complex molecules complex 3-D shape hemoglobin AP Biology Rubisco growth

hormones Amino acids Structure central carbon amino group carboxyl group (acid) R group (side chain) H O H || | N

C COH H | R variable group different for each amino acid confers unique chemical properties to each amino acid like 20 different letters of an AP Biology alphabet can make many words (proteins)

Oh, I get it! amino = NH2 acid = COOH Effect of different R groups: Nonpolar amino acids nonpolar & hydrophobic AP Biology Why are these nonpolar & hydrophobic? Effect of different R groups: Polar amino acids

polar or charged & hydrophilic AP Biology Why are these polar & hydrophillic? Ionizing in cellular waters AP Biology H+ donors Ionizing in cellular waters AP Biology

H+ acceptors Sulfur containing amino acids Form disulfide bridges covalent cross links betweens sulfhydryls stabilizes 3-D structure H-S S-H You wondered why perms smell like

rotten eggs? AP Biology Building proteins Peptide bonds covalent bond between NH2 (amine) of one amino acid & COOH (carboxyl) of another CN bond H2O dehydration synthesis

AP Biology peptide bond Building proteins Polypeptide chains have direction N-terminus = NH2 end C-terminus = COOH end repeated sequence (N-C-C) is the polypeptide backbone

can only grow in one direction AP Biology Protein structure & function Function depends on structure 3-D structure twisted, folded, coiled into unique shape pepsin

hemoglobin AP Biology collagen 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! AP Biology lysozyme: enzyme in tears & mucus that kills bacteria Sickle cell anemia Im hydrophilic! AP Biology

Just 1 out of 146 amino acids! But Im hydrophobic! 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 AP Biology Secondary (2) structure AP Biology

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

AP Biology sulfurs in sulfhydryls (SH) anchors 3-D shape Quaternary (4) structure More than one polypeptide chain bonded together only then does polypeptide become functional protein hydrophobic interactions AP Biology = skin & tendons

collagen hemoglobin Protein structure (review) R groups hydrophobic interactions disulfide bridges (H & ionic bonds) 3 multiple polypeptides hydrophobic

interactions 1 amino acid sequence peptide bonds determined by DNA AP Biology 4 2 R groups

H bonds Protein denaturation Unfolding a protein In Biology, size doesnt matter, SHAPE matters! 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 AP Biology EAT

Lets build X some Proteins! AP Biology 2008-2009 Ghosts of Lectures Past (storage) AP Biology

2007-2008 Chaperonin proteins Guide protein folding AP Biology provide shelter for folding polypeptides keep the new protein segregated from cytoplasmic influences Protein models Protein structure visualized by

X-ray crystallography extrapolating from amino acid sequence computer modelling lysozyme AP Biology

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