Most thunderstorms form by a cycle that has three stages: the cumulus stage, the mature stage, and dissipating stage. the sun heats the earth's surface during the day. the heat on the surface and warms the air around it. since warm air is lighter than cool air, it starts to rise (known as an updraft)

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.