1. Chapter 11 Protein
Proteins are mainly composed of the elements carbon, hydrogen, oxygen, and nitrogen
Proteins are made up of subunits called organic acids which contain carboxyl groups (-COOH)
Organic acids in proteins are called amino acids

2. Amino Acids
Amino acids have three parts to their structure; a side chain of carbon and hydrogen atoms, a carboxyl group, and an amine group.
An amine group contains one nitrogen and two hydrogen atoms, (-NH2)
When two amino acids join together the bond is called a peptide bond

3. Amino Acids
There are 20 amino acids that are necessary for the body to remain healthy, grow, and maintain body functions
Eight of these amino acids cannot be produced in the body and are classified as essential amino acids
Essential amino acids- amino acids that must be supplied by foods in the diet

4. Complete vs. Incomplete Proteins
Complete proteins- foods that contain all 8 essential amino acids
Most come from animal sources and are high quality proteins, ex. eggs, milk, fish, poultry, meats
Incomplete proteins- foods that are short of one or more of the 8 essential amino acids needed for human growth
Most come from grains, nuts, vegetables, and legumes

5. Protein Structures
There are infinite numbers of protein structures but they can be classified in three ways.
1. Primary structure
2. Secondary structure
3. Tertiary structure

6. Primary Structure
Primary structure of a protein molecule is the order the amino acids occur in the chain
A result of the chain of peptide bonds formed in making the protein molecule

7. Secondary Structure
Secondary structure of a protein molecule refers to the shape of sections of the amino acid chain
The three patterns of secondary structures are the helix, random coil, and the pleated sheet

8. Tertiary Structure
Tertiary structure of a protein molecule refers to the three-dimensional structure of an entire amino acid chain
The two main tertiary structures are globular (balled up) and fibrous (strands)
Globular proteins- hemoglobin, lipoprotein, casein, and albumin
Fibrous proteins- helix shaped strands,ex. collagen, elastin, keratin, myosin are all found in muscle fibers, ligaments, tendons, hair and fingernails

9. Hydrophobic Interactions
A common interaction between protein molecules is a hydrophobic, or water repelling, interaction that occurs between nonpolar side chains with carbon rings
Casein, found in milk, is an example of a hydrophobic protein and is vital to the formation of curds in cheese making

10. Oxidation and Reduction
The reversible process of adding and removing oxygen to a compound is called oxidation and reduction
Oxidation adds oxygen to a compound
Reduction removes oxygen from a compound

11. Denaturation of Proteins
Denaturation- Any change of the shape of a protein molecule without breaking peptide bonds and usually results in a loosening or unfolding of the protein molecule
Denaturation is occasionally reversible but it is not when disulfide cross-links are broken

12. Causes of Denaturation
Hot and cold temperatures
Mechanical actions
Sound waves
Pressure
Irradiation
pH changes
Mineral salts

13. Heat and Denaturation
The rate of increase for protein denaturation is 600 times for every 10ºC increase in temperature

14. Coagulation
Coagulation- a type of permanent denaturation when a liquid or semiliquid protein forms solid or semisoft clots.
Example- milk curdling to form cheese