Proteins are an important class of molecules found in all living cells. A protein is composed of one or more long chains of amino acids, the sequence of which corresponds to the DNA sequence of the gene that encodes it. Proteins play a variety of roles in the cell, including structural (cytoskeleton), mechanical (muscle), biochemical (enzymes), and cell signaling (hormones). Proteins are also an essential part of diet.
Many genes in the genome code for proteins. These are molecules of amino acids linked together in a very specific sequence that produce a functional molecule that can fold up to either be an enzyme, or a formed part of the structure of the cell, or to be secreted and act as signals. In all, there are thousands and thousands of proteins that your cells and body makes every single day. In the human genome, there are approximately 20,000 genes that code for proteins.- Lawrence C. Brody, Ph.D.