Phosphatases are a family of enzymes that remove phosphate groups from specific proteins; these phosphate groups had been added to the proteins by protein kinases. vanadate is an inhibitor of phosphatases in eukaryotic cells. what effect would vanadate have on the response of cells to signals received by receptor kinases? \

Kinases would stop working too.

Explanation:

Cells work constantly to maintain homeostasis or equilibrium within themselves. One of the mechanisms used for this purpose is feedback. As mentioned in the question, kinases put phosphates on proteins, and then, phosphatases take them off. Therefore, for phosphatases to work, kinases must be working at the same pace. By inhibiting the phosphatases the number of phosphate-proteins will be too high. This can be perceived by the kinases and they will automatically stop working since there's an excess of product. That process is called feedback.  

i think it is true in my reasonment ..