1 / 23

Proteins

Proteins . Proteins. Multipurpose molecules. Proteins . Most structurally & functionally diverse group of biomolecules Function: involved in almost everything enzymes (pepsin, polymerase, etc.) structure (keratin, collagen) carriers & transport (membrane channels)

ranee
Télécharger la présentation

Proteins

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Proteins

  2. Proteins Multipurposemolecules

  3. 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)

  4. 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 hemoglobin growthhormones Rubisco

  5. H O | —C— | H || C—OH —N— H Amino acids • Structure: • central carbon • amino group • carboxyl group (acid) • R group (side chain) • variable group • confers unique chemical properties of the amino acid R

  6. nonpolar & hydrophobic Nonpolar amino acids Why are these nonpolar & hydrophobic?

  7. polar or charged & hydrophilic Polar amino acids Why are these polar & hydrophillic?

  8. Sulfur containing amino acids • Formdisulfide bridges • cross links betweens sulfurs in amino acids H-S – S-H You wonderedwhy permssmelled like rotten eggs?

  9. peptidebond Building proteins • Peptide bonds • linking NH2 of one amino acid to COOH of another • C–N bond dehydration synthesis

  10. Protein models • Protein structure visualized by • X-ray crystallography • extrapolating from amino acid sequence • computer modelling lysozyme

  11. Building proteins • Polypeptide chains • N-terminus = NH2 end • C-terminus = COOH end • repeated sequence (N-C-C) is the polypeptide backbone • can only grow in one direction

  12. hemoglobin collagen Protein structure & function • Function depends on structure • 3-D structure • twisted, folded, coiled into unique shape pepsin

  13. 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

  14. Sickle cell anemia

  15. Secondary (2°) structure • “Local folding” • folding along short sections of polypeptide • interaction between adjacent amino acids • H bonds between R groups • -helix • -pleated sheet

  16. “Let’s go to the video tape!” (play movie here) Secondary (2°) structure

  17. 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)

  18. Quaternary (4°) structure • More than one polypeptide chainjoined together • only then is it a functional protein • hydrophobic interactions collagen = skin & tendons hemoglobin

  19. Chaperonin proteins • Guide protein folding • provide shelter for folding polypeptides • keep the new protein segregated from cytoplasmic influences

  20. 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!

  21. multiplepolypeptides hydrophobic interactions aa sequence peptide bonds determinedby DNA R groups H bonds Protein structure (review) R groups hydrophobic interactions, disulfide bridges 3° 1° 2° 4°

  22. Let’s build some Proteins!

  23. Any Questions??

More Related