2. Regents Biology Proteins

3. Regents Biology 2006-2007 Proteins: Multipurpose molecules

4. Regents Biology collagen (skin) Proteins insulin Examples  muscle  skin, hair, fingernails, claws  collagen, keratin  pepsin  digestive enzyme in stomach  insulin  hormone that controls blood sugar levels pepsin

5. Regents Biology Proteins  Function:  many, many functions  hormones  signals from one body system to another  insulin  movement  muscle  immune system  protect against germs  enzymes  help chemical reactions

6. Regents Biology Amino acids  Structure  central carbon  amino group  carboxyl group (acid)  R group (side chain)  variable group  different for each amino acid  confers unique chemical properties to 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 = NH2 acid = COOH

7. Regents Biology Proteins  Building block = amino acid amino acid – amino acid – amino acid – amino acid – —N——N— H H H | —C— | C—OH || O variable group amino acids  20 different amino acids There’s 20 of us… like 20 different letters in an alphabet! Can make lots of different words

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

9. Regents Biology Effect of different R groups: Polar amino acids  polar or charged & hydrophilic Why are these polar & hydrophillic?

10. Regents Biology Ionizing in cellular waters H+ donors

11. Regents Biology Ionizing in cellular waters H+ acceptors

12. Regents Biology Sulfur containing amino acids  Form disulfide bridges  covalent cross links betweens sulfhydryls  stabilizes 3-D structure You wondered why perms smell like rotten eggs? H-S – S-H

13. Regents Biology Amino Acids  Essential Amino acids  Amino acids that the body cannot synthesize from simpler compounds; they must be obtained from the diet

14. Regents Biology Amino acid chains  Proteins  amino acids chained into a polymer —N——N— H H H | —C— | R C—OH || O —N——N— H H H | —C— | R C—OH || O

15. Regents Biology Amino acid chains  Proteins  amino acids chained into a polymer —N——N— H H H | —C— | R C—OH || O —N——N— H H H | —C— | R C—OH || O Carboxyl group Amino group

16. Regents Biology Amino acid chains  Proteins  amino acids chained into a polymer —N——N— H H H | —C— | R C— || O —N——N— H H | —C— | R C—OH || O OH H

17. Regents Biology Amino acid chains  Proteins  amino acids chained into a polymer —N——N— H H H | —C— | R C— || O —N——N— H H | —C— | R C—OH || O H2OH2O Peptide bond- The amide linkage that holds amino acids together in polypeptides

18. Regents Biology Amino acid chains  Proteins  amino acids chained into a polymer  Each amino acid is different  some “like” water & dissolve in it  some “fear” water & separate from it amino acid

19. Regents Biology Amino acid chains  Amino terminus  The free amino group at one end of the polypeptide  Carboxyl terminus  The free carboxyl group at one end of a polypeptide amino acid

20. Regents Biology Water-fearing amino acids  Hydrophobic  “water fearing” amino acids  try to get away from water in cell  the protein folds

21. Regents Biology Water-loving amino acids  Hydrophillic  “water loving” amino acids  try to stay in water in cell  the protein folds

22. Regents Biology pepsin For proteins: SHAPE matters! collagen  Proteins fold & twist into 3-D shape  that’s what happens in the cell!  Different shapes = different jobs hemoglobin growth hormone

23. Regents Biology It’s SHAPE that matters!  Proteins do their jobs, because of their shape (conformation)  Unfolding a protein destroys its shape  wrong shape = can’t do its job  unfolding proteins = “denature”  temperature  pH (acidity) folded unfolded “denatured” In Biology, it’s not the size, it’s the SHAPE that matters!

24. Regents Biology Protein Folding  Shape comes from how the protein folds  There are 4 levels of folding in proteins

25. Regents 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 & its function  even just one amino acid change can make all the difference! lysozyme: enzyme in tears & mucus that kills bacteria

26. Regents Biology 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

27. Regents Biology Secondary (2°) structure

28. Regents 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 sulfurs in sulfhydryls (S–H)  anchors 3-D shape

29. Regents Biology Quaternary (4°) structure  More than one polypeptide chain bonded together  only then does polypeptide become functional protein  hydrophobic interactions  Protein structure video Protein structure video collagen = skin & tendons hemoglobin

30. Regents 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°