Protein

- Proteins account for more than 50% of dry weight of most cells

7 Classes of Proteins:
1. Structural Proteins (function in cell membrane)
2. Contractile Proteins (provide muscular movement)
3.Storage Proteins (a source of amino acid for developing embryos)
4. Defensive Proteins (antibodies carried in blood)
5. Transport Proteins (hemoglobin, transports oxygen from lungs)
6. Enzymes (regulate chemical reactions in cells)
7. Hormones (chemical messenger)

- proteins are made from 20 amino acids
- bonded together by peptide bonds (dehydration synthesis reaction)

- 9 amino acids are essential
1 amino acid = 1 amino acid monomer
2 amino acid = dipeptide molecule
many amino acid = polypeptide chain
1 or more polypeptide chains = a protein molecule

secondary structure:
- connected by hydrogen bonds
- 2 types (alpha helix and beta pleated sheet)
       1. alpha helix: flexible, coiled
       2.beta pleated sheet: strong, parallel

tertiary structure:
- folded
- hydrogen bond
- ionic bond
- di-sulfide bridges occur between neighbouring cysteine amino acids
- 2 types (fibrous and globular)
1. fibrous: strong, insoluble in water
2. globular: spherical, hydrophobic inside, hydrophilic outside, soluble in water

- reducing agent breaks down di-sulfide bridges
- oxidizing agent (H peroxide) helps reform bridges

Quaternary structure:
- 2 or more polypeptide chains linked together

Denatured Proteins:
- proteins that cannot perform properly
- chemicals and or heat disrupts the bonds within proteins