Digestion is the complex biological process by which large, complex food molecules are broken down into smaller, absorbable units that the body can utilize for energy, growth, and metabolic functions. This process begins in the mouth with mechanical chewing and initial chemical breakdown, continues through the acidic environment of the stomach, and progresses through the intestines. Digestive enzymes catalyze the breakdown of macronutrients—carbohydrates, proteins, and fats—into their fundamental components (sugars, amino acids, and fatty acids, respectively). These smaller molecules then pass through the intestinal wall into the bloodstream and lymphatic system, where they are distributed to various cells and organs. The remaining undigested material is eliminated from the body.