C) Proteins

. Proteins:

-- contain the elements carbon, hydrogen, oxygen, and nitrogen

-- composed of amino acid subunits (below is the structure of an amino acid)

[Major Protein Functions]

1. Growth and repair

2. Energy

3. Buffer -- helps keep body pH constant

dipeptide -- formed from two amino acid subunits

Dehydration synthesis of a dipeptide

amino acid + amino acid ----- dipeptide + water

Hydrolysis of a dipeptide

dipeptide + H2O ---> amino acid + amino acid

polypeptide (protein) -- is composed of three or more amino acids linked by synthesis reactions

Examples of proteins include insulin, hemoglobin, and enzymes.

** There are an extremely large number of different proteins. The bases for variability include differences in the number, kinds and sequences of amino acids in the proteins