Sulfur and phosphorus compounds enter bodies of water, such as ponds, lakes, and rivers a) from the decomposition of rocks found on the bottom of bodies of water. b) as by-products of photosynthesis carried out by aquatic plants. c) as run-off containing fertilizers and detergents. d) as a by-product of algal blooms.

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.