In __, the second stage of food processing, food is broken down into molecuels small enough for the body to absorb. This stage is necessry because animals cannot directyl use proteins, carbs, nucleic acids, fats and phospholipids in food. These molecuels are too large to pass through membranes and enter the cells of the animal. In addition, the large molecuels in food are not all identical to those the animal needs for its particular tissue and fucntions. When large molecuels in food are broken down into their components, the animal can use these smaller molecules to assemble the large molecules it needs.