Proteins Are Molecular Workers

Most enzymes are a type of polymeric molecule called protein. Proteins are chains of amino acids. Twenty different amino acid types are found in living cells. When joined in a protein, the amino acids interact. Particular amino acids attract; others repel. The order of amino acids in a protein chain and the length of the chain determine the three-dimensional structure of a given protein molecule. That structure then determines how the protein functions in the cell. Differences among organisms can be reduced to differences in their proteins. Because protein length can range from less than a hundred to more than several thousand amino acids, an astronomical number of different protein molecules can exist. (For example, a chain of 100 amino acids could come in 20¹⁰⁰ combinations—20 times 20 one hundred times). That gives life forms tremendous potential for diversity.