"???" - snowbird
If you wish to assert something like the cell is designed, rather than the product of non-guided process you either have to bring the designer forwards to explain how it was all done (or to simply say "yeah it was me, good eh?") or demonstrate that there is no natural process that could bring it about.
For the latter you would have to know everything so as to not overlook a potential natural process. You can't just say "I can't think of an explanation therefore..." or "I can't see how it could have happened naturally..." because that is nothing more than an argument from ignorance/incredulity and as such is logically flawed.