1. Protein (cont.) Definition
Protein from the Greek proteios, meaning primary or “first place”.
Our genes code for proteins
Protein make up more than 50% of the dry mass of cells.

2. Roles played by proteins include:
Enzymes (biological catalysts)
Hormones
Storage proteins
Transport proteins
Structural proteins
Protective proteins
Contractile proteins
Toxic proteins
Proteins in the Diet
9 of the 20 amino acids must be obtained from the diet (these are referred to as the essential amino acids).
Proteins are also the major source of nitrogen in the diet.

3. Protein Structure Dipeptide – 2 amino acids Tripeptide – 3 amino acids
Oligopeptides – 4-10 amino acids
Polypeptide – more than 10 amino acids
Proteins in the body and diet are long polypeptides (100s of amino acids)
Collagen: the most abundant protein in mammals, and gives bone and skin their strength
Keratin: provides structure to hair and nails

4. 4 levels of protein structure

5. 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

6. Worldwide Lactose intolerance

7. Denaturation
Disruption of secondary, tertiary and quaternary protein structure by
heat/organics
Break apart H bonds and disrupt hydrophobic attractions
acids/ bases
Break H bonds between polar R groups and ionic bonds
heavy metal ions
React with S-S bonds to form solids
agitation
Stretches chains until bonds break

8. Applications of Denaturation
Hard boiling an egg
Wiping the skin with alcohol swab for injection
Cooking food to destroy E. coli.
Heat used to cauterize blood vessels
Autoclave sterilizes instruments
Milk is heated to make yogurt