ABSTRACT
Absorption of the nutrients is a process of great complexity, often involving the participation of intracellular enzymes, transport proteins, and ion pumps. Gastrointestinal proteins are hydrolyzed to their constituent amino acids, di- and tripeptides. Soluble proteins and proteins that have been denatured are most readily hydrolyzed. All of the digestive enzymes, components of the pancreas, mucosal secretions, and exfoliated tissues of the intestinal lumen are subject to digestion right along with dietary protein. For most people, carbohydrates in the diet provide the largest contribution of total caloric need and singularly account for the largest nutrient mass ingested. The absorption of lipids and the products of lipid digestion from the intestinal lumen is complex, owing to the variety of lipids in the diet, the participation of the bile acids in micelle formation, and the intracellular synthesis of triglycerides within the microvilli.
