The Wonderful World of Proteins

1. The Wonderful Worldof Proteins Types of Proteins Amino Acids The Peptide BondProtein Structure

2. Types of Proteins Type Examples • Structural tendons, cartilage, hair, nails • Contractile muscles • Transport hemoglobin, myoglobin • Storage milk, nuts, seeds • Hormonal insulin, growth hormone • Enzyme catalyzes reactions in cells • Protection immune response

3. Amino Acids • Building blocks of proteins • Carboxylic acid group • Amino group • Side group R gives unique characteristics Rside chain (variable) I H2N—C —COOH I H

4. Examples of Amino Acids H I H2N—C —COOH I H glycine CH3 I H2N—C —COOH I H alanine

5. Types of Amino Acids Nonpolar Polar Polar/Acidic Polar/ Basic Amino acids each have their own unique chemical properties. Some dissolve in water – some do not. This is essential for transport and storage.

6. Essential Amino Acids • 10 amino acids not synthesized by the body • arg, his, ile, leu, lys, met, phe, thr, trp, val • Must obtain from the diet • All in diary products • 1 or more missing in grains and vegetables

7. The Peptide Bond Bond formed by the –COOH of an amino acid and the –NH2 of the next amino acid O CH3 + || + | NH3–CH2–COH + H3N–CH–COO– O CH3 + ||| NH3–CH2–C – N–CH–COO– | peptide bond H

8. Peptides • Amino acids linked by peptide bonds Gly Lys Phe Arg Ser H2N- -COOH end Peptide bonds end Glycyllysylphenylalanylarginylserine

9. Protein Structure Primary and Secondary Structure Tertiary and Quaternary Structure Protein Hydrolysis and Denaturation

10. Primary Structure of Proteins The particular sequence of amino acids that is the backbone of a peptide chain or protein Ala-Leu-Cys-Met

11. Secondary Structure – Alpha Helix • Three-dimensional arrangement of amino acids with the polypeptide chain in a corkscrew shape • Held by H bonds Looks like a coiled “telephone cord”

12. Secondary Structure – Beta Pleated Sheet • Polypeptide chains are arranged side by side • Hydrogen bonds form between chains • Typical of fibrous proteins such as silk

13. Secondary Structure – Triple Helix • Three polypeptide chains woven together • Typical of collagen, connective tissue, skin, tendons, and cartilage

14. Tertiary Structure • Specific overall shape of a protein • Examples of cross links between R groups of amino acids in chain disulfide –S–S– + ionic –COO– H3N– H bonds C=O HO– hydrophobic –CH3 H3C–

15. Globular and Fibrous Proteins Globular proteins Fibrous proteins “spherical” shape long, thin fibers Insulin Hair Hemoglobin Wool Enzymes Skin Antibodies Nails Spider web

16. Quaternary Structure • Proteins with two or more chains • Example is hemoglobin Carries oxygen in blood Four polypeptide chains Each chain has a heme group to bind oxygen

17. Protein Hydrolysis • Break down of peptide bonds • Requires acid or base, water and heat • Gives smaller peptides and amino acids • Similar to digestion of proteins using enzymes • Occurs in cells to provide amino acids to synthesize other proteins and tissues

18. Hydrolysis of a Dipeptide

19. Denaturation Disruption of secondary, tertiary and quaternary protein structure by heat/organics acids/ bases heavy metal ions agitation Basically the protein is unfolded without changing the primary structure resulting in the protein changing its’ physical properties.

20. Examples of Denaturation Frying or boiling an egg Ironing or curling your hair Alcohol on cuts to denature proteins in bacteria Cooking food to denature proteins in bacteria