A protein is created from twenty simple chemicals named amino acids—Methionine, Glycine, Leucine, and so forth—strung together in a chain. Unlike a chain of DNA, which exists primarily in the form of a double helix, a protein chain can twist and turn in space idiosyncratically, like a wire that has been sculpted into a unique shape. This shape-acquiring ability allows proteins to execute diverse functions in cells. They can exist as long, stretchable fibers in muscle (myosin). They can become globular in shape and enable chemical reactions—i.e., enzymes (DNA polymerase). They can bind colored
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