3.3.3: Digestion & Absorption

• -> Explain the process for lipid digestion.

  • (Big) lipid droplet is mixed with bile salts produced by the liver and gallbladder -> emulsification
  • Emulsification causes small lipid droplets to form micelles (smaller lipid droplets)
  • Pancreatic lipase hydrolyses ester bonds of micelles to form monoglycerides and fatty acids (which can recombine constantly)
  • Monoglycerides and fatty acids enter epithelial cells of ileum via simple diffusion
  • Reach the rough E.R, recombine to form triglycerides
• Explain the process for lipid digestion (cont.)

  • Associate with cholesterol and lipoproteins -> chylomicrons
  • Chylomicrons exit cell via exocytosis in lacteals through to lymphatic system
  • Enter bloodstream
  • Enzymes in capillary endothelial cells hydrolyse chylomicrons
  • Products diffuse into cells as needed.
• Absorption of glucose

  • AT of Na+ from epithelial cells of ileum to capillaries/blood (concentration gradient established between epithelial & capillaries)
  • Co-transport of glucose & Na+ TOGETHER through symport Na+ dependent co-transporter protein back into epithelial cell
  • Glucose diffuses into bloodstream via facilitated diffusion accordingly