Why do people, animals, and all other organisms do cellular respiration? O To make food/glucose for themselves. As a byproduct they make the oxygen that we need.
O To make carbon dioxide and water that animals can use.
O To make ATP (cell energy). Carbon dioxide and water are also produce as byproducts.
To make oxygen, carbon dioxide, and glucose for themselves.

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.