Which of the following is an example of internal regulation during the cell cycle? A gap outside of the cell (caused by a skateboarding accident) triggers cell division.
A cell receives a signal from the cell’s own nucleus to divide.
Tumor cells continue to divide without receiving a signal.
Hormones in the blood cause cell growth in a growing teenager.

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.