"respond as a human would"? Which human? A sleeping one? Mentally ill? Mute? A fetus? Frenchman?
Terri Shiavo? I guarantee I can make a computer that responds more "as a human would" in your mind than someone in a persistent vegetative state would respond. Surely you aren't defining humanity by such criteria?
I certainly have the resources to reproduce a human, as (according to my wife

) I've done it 3 times already. And when you say "function as a human" you're again treading into an extremely subjective area which was my point above. You think you know what a human is, but I doubt you've given it much thought. Is a person missing a hand still human? What about a person missing a face? What about a being with partial brain damage? Does the amount of brain damage matter? If so, how much? What about a living yet disembodied brain?
My point is you must first specifically define terms before I can say whether or not humans can or will ever be able to achieve the accomplishments in your head.