Proteins Amino acids structure Peptide bonds (condensation reaction)

Protein Structures Primary Structures: peptide bonds between amino acids Secondary Structures: hydrogen bonds between COOH & NH2 of different AA Tertiary Structures: disulfide bonds between variable side groups Quaternary Structures: multiple polypeptides

Primary Structure … Try – Gly – Lys – Pro – Val – Arg – Glu … N-terminal C-terminal

Secondary Protein Structure: hydrogen bonds Alpha-helix Beta-pleated sheets

HEAT Proteins are wound-up, and held together by disulfide & hydrogen bonds. Denaturation – change of molecular shape (unwind), and hydrogen bonds are broken. Coagulation - liquid  semisolid HEAT

Denaturation Beating an egg Cooking an egg

Denaturation Thermal denaturation (stable 47-67°C) Ionic strength/pH (disrupt H-bonds) Mechanical treatment (beating) Lab: Effect of Acid on Proteins

Effects of Acid on Proteins How does gastric juice facilitate protein digestion? Outer-most layer of protein denatures and coagulates first Key words: H+ ions, hydrogen and disulfide bonds

Anatomy of an Egg

Some Parts You Can Name… Albumin (white) Yolk Shell: pores

Shell Texture Pores

Inner & Outer Membrane Protection Air cell in between Semi-permeable

Air Cell Location Formed after being laid

Albumen > 50% of an egg ~ 90% water 40 different proteins Thick & thin albumen

Chalazae opaque twisted cordlike anchoring the yolk prominent in fresh eggs

Vitelline Membrane enclosing the yolk

Yolk even more protein, less water vitamins (A, B, D) mineral (Fe, Ca, P) some fats

Denaturation