1. Protein Structure
Over 50% of the body’s dry mass is protein; proteins are the most important organic molecule in the body.
The building blocks of proteins are amino acids.
26 amino acids exist in nature; humans require 20 to make the proteins we need.
Amino acids are manufactured by plants and some bacteria; animals cannot make amino acids unless they eat plants or eat animals that eat plants.

2. Function of Proteins Proteins function as:
Regulatory: Enzymes and hormones are proteins..(control the rate of all metabolic reactions; either anabolic or catabolic).
Structural protein; muscle fibers, connective tissue, hair and tendons are all composed of protein.

3. Basic Structure of an Amino Acid
All amino acids contain an amino group and a
Carboxylic acid group; these functional groups are
“sticky,” that is, they are charged and can form bonds with
each other.

4. Here are the structures
of the 20 amino
acids needed by the
body; Note the pink
highlighted areas
are the same amongst
all of the acids; these
are the carboxylic
acid and amino groups.

5. Joining Amino Acids to Form a Peptide Bond

6. Peptide Bond Continued…

7. Peptide Bond Animations
Protein folding
Protein denaturature egg whites

8. MILK PROTEIN: “Curds” and “Whey”
Milk contains two major proteins:
“casein” found in the curds (cheese)
“whey” found in the liquid left over after cheese is made

9. MILK PROTEINS..structure of milk
Milk is a colloid, that is, a mixture of two or more substances that will separate over time due to large particle size.

13. Casein protein is an Emulsifier, that is, the casein molecule contains both a polar (charged) section and a nonpolar (uncharged) section making the casein molecule both hydrophillic and hydrophobic.