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.

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.

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 levels of protein structure

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

Worldwide Lactose intolerance http://www.britannica.com/science/human-nutrition/images-videos/Global-distribution-of-lactose-intolerance-in-humans/157598

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

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