Is it impossible to design an importer protein that can selectively import certain molecules without using energy? If not, why?

Ans.:
Cell has high concentration of different substances, it requires energy (we have to do it forcibly, and will not occur spontaneously by itself) so it has some energy stored in this way.
One of the fundamental principles of physics is that entropy of the universe never decreases. To continue living, cell has to concentrate some definite substances inside the cell; this process leads to a decrease in entropy. So according to aforesaid principle, entropy must increase in some other processes. Entropy can increase by simultaneous diffusion of some other substances or simply by dissipation of energy- namely heat. So in principle, it is impossible to design an importer protein that can selectively import certain molecules without using energy of any form (energy can be stored in concentration gradient which can also be harnessed in active transport process).

transpiration

Chain of water molecule – evaporating at one end.
The evaporating molecule must move up, with an upward drag. To make the drag more efficient it will be good idea to make a vacuum tube. But even vacuum tube has a limit because after reaching certain height two opposing process gravity and transpiration-drag will reach equilibrium. Solution is adhesion of water molecule to xylem vessel, transferring weight of the water column to the tree itself. Now we have got rid of gravity.
What we'll do when gas bubbles breaks the chain. Answer is make new fibre. Simple!