What Is a Molecular Machine and Why Is It Irreducibly Complex?
Molecular machines are complex structures located inside of cells or on the surface of cells. One popular example is the bacterial flagella. This whip-like structure is composed of many proteins, and its rotation propels bacteria through their environment. The molecular machine of interest in a recent PNAS article is a protein transport machine located in the mitochondria.2 This machine transports proteins across the membrane of mitochondria so they can perform the very important function of making energy. Molecular machines are considered to be irreducibly complex. An irreducibly complex machine is made of a number of essential parts, and all these parts must be present for it to function properly. If even one of these parts is missing the machine is non-functional. Evolution, which supposedly works in a stepwise fashion over long periods of time, can’t form these complex machines. Evolution is not goal-oriented; it cannot work towards a specific outcome. If a part of the machine woul
