Often we look at complex machinery and associate meanings or parallels to biological systems, however this is an incorrect perspective. No matter how sophisticated the machine is, it is invariably only a tool and as such needs to be examined from that viewpoint.
Consider a simple tool like the hammer. It is clear that the purpose is to be able to extend the functionality of the hand by using it to pound nails. This is something that is beyond the ability of our hand to do, but with this extension the hand can be transformed. Similarly with inventions like the typewriter, leading up to word processors, each of these simply becomes an extension of our bodies to do things either faster, or with greater efficiency that more primitive mechanisms would allow.
The invention of an airplane isn't intended to replicate a bird's flight, but rather to serve as a tool that allows humans to fly.
The point here is that all tools are simply biological extensions and have no purpose or use outside of that realm. A word processor cannot simply generate a document on its own, nor can an plane decide to take a trip. Each of these is directed by humans to perform a specific task.
From this it becomes easier to see how even robots and seemingly "intelligent" devices are merely extensions of human behavior that we've been able to encode to replicate things we would ordinarily do. A computer may be able to perform tasks better or faster than a human, but that is fundamentally as meaningless as comparing a car to an long distance runner. That's the point of our tools, is to do things better than we can do them ourselves using only our biology.
The difficulty in separating these viewpoints occurs when our tools become increasingly sophisticated and are capable of behaving in ways that replicate other biological systems. However, the key element is that they are still acting according to our directed intentions.
For living things it seems obvious that there is a transition point, or emergent property that exists so that an organism's behavior can become self-directed beyond the mere chemistry of its existence. That self-direction invariably involves acquiring food/energy, reproduction, and defense.
While we can certainly build machines that can replicate such activities, they are as different from life as the Mona Lisa is when compared to a paint by numbers version of it.
However, it seems that the one element of biological systems that is different from all else, is that biological systems adapt and evolve through the vehicle of reproduction. It is this characteristic that distinguishes organic molecules like those that make up snake venom from viruses. While both may elicit an immunization type of response, only the latter has the means of reproducing and growing albeit with hijacked mechanisms.
Perhaps it is this latter perspective that also suggests the most serious flaw of Intelligent Design, in that no matter what object we select for complexity, it cannot behave in any way that isn't a reflection of the humans that created it. Similarly, if we considered that all biological systems were created by an intelligent designer, then it would suggest the worst sort of dependence, since we would be incapable of operating independently, but instead be a mere reflection of someone else's intent.
1 It is not my intent to engage in the debate of when chemistry becomes life, which is akin to asking when a screw or bolt becomes a plane.