Actuan las hormonas solo sobre celulas o pueden actuar sobre otras estructuras?

Hormones act only on cells not structures.

Explanation:

Hormones act only on cells and they  do not act on other structures because there are specific cells have receptors for that particular hormone. Some hormones bind itself to the receptors on the surface of target cells whereas other hormones enter the cells and bind itself to the receptors present in the cytoplasm or nucleus of the cell.

cramming before a final is bad because it makes a student's stress level higher. students who embrace cramming to get through a final exam week find themselves struggling to perform consistently, once the brain adjusts to prolonged sleep deprivation.

enzyme speed up the reactions