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AP Biology Proteins
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AP Biology 2006-2007 Proteins Multipurpose molecules
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AP Biology Proteins Most structurally & functionally diverse group of biomolecules Function: involved in almost everything enzymes (pepsin, polymerase, etc.) structure (keratin, collagen) carriers & transport (membrane channels) receptors & binding (defense: antibodies) contraction (actin & myosin) signaling (hormones: insulin) storage (bean seed proteins)
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AP Biology Proteins Structure: 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 Rubisco hemoglobin growth hormones
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AP Biology Amino acids Structure: central carbon amino group carboxyl group (acid) R group (side chain) variable group confers unique chemical properties of the amino acid —N——N— H H C—OH || O R | —C— | H
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AP Biology Nonpolar amino acids nonpolar & hydrophobic Why are these nonpolar & hydrophobic?
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AP Biology Polar amino acids polar or charged & hydrophilic Why are these polar & hydrophillic?
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AP Biology Sulfur containing amino acids Form disulfide bridges cross links betweens sulfurs in amino acids You wondered why perms smelled like rotten eggs? H-S – S-H
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AP Biology Building proteins Peptide bonds linking NH 2 of one amino acid to COOH of another C–N bond peptide bond dehydration synthesis
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AP Biology Protein models Protein structure visualized by X-ray crystallography extrapolating from amino acid sequence computer modelling lysozyme
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AP Biology Building proteins Polypeptide chains N-terminus = NH 2 end C-terminus = COOH end repeated sequence (N-C-C) is the polypeptide backbone can only grow in one direction
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AP Biology Protein structure & function hemoglobin Function depends on structure 3-D structure twisted, folded, coiled into unique shape collagen pepsin
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AP Biology 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 & it’s function even just one amino acid change can make all the difference! lysozyme: enzyme in tears & mucus that kills bacteria
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AP Biology Sickle cell anemia
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AP Biology Secondary (2°) structure “Local folding” folding along short sections of polypeptide interaction between adjacent amino acids H bonds between R groups -helix -pleated sheet
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AP Biology Secondary (2°) structure “Let’s go to the video tape!” (play movie here)
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AP Biology Tertiary (3°) structure “Whole molecule folding” determined by interactions between R groups hydrophobic interactions effect of water in cell anchored by disulfide bridges (H & ionic bonds)
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AP Biology Quaternary (4°) structure More than one polypeptide chain joined together only then is it a functional protein hydrophobic interactions hemoglobin collagen = skin & tendons
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AP Biology Chaperonin proteins Guide protein folding provide shelter for folding polypeptides keep the new protein segregated from cytoplasmic influences
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AP Biology Denature a protein Unfolding a protein disrupt 3° structure pH salt temperature unravels or denatures protein disrupts H bonds, ionic bonds & disulfide bridges destroys functionality Some proteins can return to their functional shape after denaturation, many cannot In Biology, size doesn’t matter, SHAPE matters!
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AP Biology Protein structure (review) 1° 2° 3° 4° aa sequence peptide bonds R groups H bonds R groups hydrophobic interactions, disulfide bridges determined by DNA multiple polypeptides hydrophobic interactions
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AP Biology 2006-2007 Let’s build some Proteins!
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AP Biology 2006-2007 Any Questions??
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