Digestion and Absorption
Start with the big picture
Digestion combines luminal enzymes from saliva, the stomach, and pancreas with brush border enzymes on enterocytes. Carbohydrates must become monosaccharides: glucose and galactose use sodium-linked SGLT-1, while fructose uses GLUT-5. Proteins are broken down by pepsin, pancreatic proteases, and brush border peptidases, then absorbed as amino acids or small peptides. Lipids depend on bile salts for micelle formation and pancreatic lipase for digestion; their products are absorbed, reassembled into chylomicrons, and enter the lymph. The topic also covers fat-soluble vitamins, vitamin B₁₂ absorption with intrinsic factor in the ileum, mineral uptake, and water and electrolyte absorption. The duodenum and jejunum absorb many nutrients, the ileum takes up bile salts and B₁₂, and the colon fine-tunes water and electrolyte absorption.
What you'll learn
- Distinguish luminal digestion from brush border digestion.
- Describe how monosaccharides are absorbed through their specific transporters.
- Summarize protein and lipid digestion and the forms in which they are absorbed.
- Explain the roles of bile salts and chylomicrons in lipid absorption.
- Identify key sites and requirements for vitamin, mineral, water, and electrolyte absorption.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
