Proteins

Proteins are composed of long chains of amino acid units, which may be sequenced in any order. This makes possible a great variety of proteins. There are, however, a limited number of amino acids, some twenty of which are of interest to biologists. Long chains of repeating units of such amino acids are called polymers.

A given type of protein has a given sequence of amino acids, as shown in figure 4-14. The characteristics (specifically, the biological properties) of a protein can be attributed to both the amino acid sequencing and the bends and folds that occur along the chain of amino acid units (which are also constant for any particular protein) (figure 4-15).

Figure 4-14 A chain of amino acids linked in a particular sequence produces a protein

Figure 4-15 The configuration of a protein shows bends at specific sites.