Discussing an article with friends we began discussing whether a protein complex that punches holes in cells (membrane attack complex) would be considered a machine.

Now, my friends are biochemistry students while I am a computer science student so this is far from my expertise. In my imagination this would be a mechanical action, hence the definition of a machine found on Wikipedia. My friends counter argument is more of an emotional one, saying it feels wrong to call it a machine but also couldn't come up with a better word.

So: Is it a machine? Is it something else? Or is a complex just a complex? Does chemistry/biology have its very own definitions for things that do stuff in coordination without being "alive"?

  • $\begingroup$ If some gaseous molecules collide, they can react to form a new compound, given they have enough energy and the right orientation. Would you call the reactants a machine? $\endgroup$ – It's Over May 27 '19 at 12:57
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    $\begingroup$ I might argue that for the distinction to be meaningful the issue would be whether a protein is manipulating something chemical (eg breaking bonds selectively) or physical (eg moving some other object or punching a hole in something without breaking specific bonds). $\endgroup$ – matt_black May 27 '19 at 12:58
  • $\begingroup$ @M.A.R. Not necessarily, I guess. But what about a protein that fold under light. Is that not technically converting energy to mechanical motion? $\endgroup$ – Harri May 27 '19 at 12:58
  • $\begingroup$ I would generalize that a machine can transform chemical energy (or other form) into mechanical energy, and can operate in a cycle, eventually returning to its original state. $\endgroup$ – Buck Thorn May 27 '19 at 13:06
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    $\begingroup$ @Harri That's how I think of one. Then again I suppose you could have a one-off (disposable) machine, probably I am imposing an unnecessary constraint with the cyclic business. en.wikipedia.org/wiki/Molecular_machine#Biological $\endgroup$ – Buck Thorn May 27 '19 at 13:13

According to the Oxford dictionary, a machine is:

An apparatus using mechanical power and having several parts, each with a definite function and together performing a particular task.

Based on that definition, I think some proteins and enzymes could definitely be considered machines. A good example for that, in my opinion, would be ATP Synthase and all of the proteins that participate in the oxidative phosphorilation process.

  • $\begingroup$ According to to the Oxford dictionary, an apparatus is 1. technical equipment or machinery [....], 2.the complex structure of a particular organization or system. 3. A collection of notes [...] - I do not really see a good fit for proteins here. But if a protein isn't an apparatus, it's not a machine either... $\endgroup$ – Arsak May 28 '19 at 11:45
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    $\begingroup$ Well, we can just keep going down the rabbit hole. According to the Oxford dictionary, technical is: "Relating to a particular subject, art, or craft, or its techniques." Seems to fit. I guess there is no clear answer because it's a question that relies heavily on semantics. $\endgroup$ – Argento May 28 '19 at 11:48
  • $\begingroup$ :) Fully agree that this question heavily relies on semantics. $\endgroup$ – Arsak May 28 '19 at 11:51
  • $\begingroup$ @Arsak Apparatus has much narrower meaning. $\endgroup$ – Mithoron May 29 '19 at 18:12

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