Question

Membrane proteins are among the most important proteins biologically because they allow cells to communicate with their environments. In humans, they determine whether the immune system recognizes the cell as foreign or not and they are the targets of most pharmaceuticals. In all organisms, membrane proteins are responsible for other functions as well. One function determines when and if cell division takes place. That is

Answer 1

One function determines when and if cell division takes place. That is activation of growth hormones.
When these hormones start forming, that is when the cell is going to be divided. 

Answer 2

C) activation of growth hormones.