2. Regents Biology Proteins

3. Regents Biology 2006-2007 Proteins: Multipurpose molecules

4. Regents Biology Proteins insulin collagen (skin) hemoglobin Examples  muscle  fingernails, claws  skin  hair  enzymes  example: pepsin  hormones  example: insulin

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

6. 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

7. 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

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

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

10. Regents Biology pepsin 3-D protein structure collagen  Proteins fold & twist into 3-D shape hemoglobin growth hormone

11. Regents Biology Proteins (Polypeptides) Four levels of protein structure: A.Primary Structure B.Secondary Structure C.Tertiary Structure D.Quaternary Structure

12. Regents Biology Primary Structure peptide bonds (straight chains) Amino acids bonded together by peptide bonds (straight chains) aa1aa2aa3aa4aa5aa6 Peptide Bonds Amino Acids (aa)

13. Regents Biology Secondary Structure primary structurecoilspleats hydrogen bonds  3-dimensional folding arrangement of a primary structure into coils and pleats held together by hydrogen bonds.  Two examples: Alpha Helix Beta Pleated Sheet Hydrogen Bonds

14. Regents Biology Tertiary Structure  Secondary structuresbent foldedmore complex 3-D arrangement  Secondary structures bent and folded into a more complex 3-D arrangement of linked polypeptides  Bonds: H-bonds, ionic, disulfide bridges (S-S) “subunit”.  Call a “subunit”. Alpha Helix Beta Pleated Sheet

15. Regents Biology Quaternary Structure  Composed of 2 or more “subunits”  Globular in shape  Form in Aqueous environments enzymes (hemoglobin)  Example: enzymes (hemoglobin) subunits

16. Regents Biology Its shape that matters!  Proteins do their jobs, because of their shape  Unfolding a protein destroys its shape  wrong shape = can’t do its job  unfolding proteins = “denature”  temperature  pH (acidity) folded unfolded “denatured”