What determines whether the cell will use the transport proteins

Some molecules can diffuse through the cell membrane without any assistance from the cell. Others require the help of transmembrane proteins to move into or out of the cell. Three primary factors determine whether a molecule will diffuse across a cell membrane: concentration, charge and size.

Explanation:

i think its control and coordinate because im pretty sure thats what tissue does and the joints are what control movement and then your skeletal/ bones provides portection. hope that .

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.