💊 Intrinsic Factor & Terminal Ileum Absorption Simulator

Dietary B12 Release in the Stomach

Placeholder sentence: acid and pepsin liberate B12 from food proteins.

• ~1.5–3: Gastric pH (Placeholder short caption)
• Pepsin: Enzyme (Placeholder short caption)
• Animal protein: B12 source (Placeholder short caption)
• Stomach lumen: Site (Placeholder short caption)

Gastric liberation of protein-bound B12

Placeholder short paragraph describing acid/pepsin release of B12.

Placeholder highlight: achlorhydria impairs this first release step.

R-protein Binding and Pancreatic Cleavage

Placeholder sentence: haptocorrin shields B12 until pancreatic enzymes act.

• Haptocorrin: Carrier (Placeholder short caption)
• Trypsin/chymotrypsin: Cleaving enzymes (Placeholder short caption)
• Duodenum: Location (Placeholder short caption)
• Acidic→alkaline: pH shift (Placeholder short caption)

R-protein transfer and proteolytic release

Placeholder short paragraph describing R-protein handoff and cleavage.

Placeholder highlight: pancreatic insufficiency can trap B12 on R-protein.

Intrinsic Factor Binding

Placeholder sentence: parietal-cell intrinsic factor captures freed B12.

• Parietal cells: Secreted by (Placeholder short caption)
• Very high: Affinity (Placeholder short caption)
• B12–IF: Complex (Placeholder short caption)
• Protease-resistant: Stability (Placeholder short caption)

Formation of the stable B12–IF complex

Placeholder short paragraph describing intrinsic factor binding.

Placeholder highlight: pernicious anemia arises from IF autoantibodies.

Terminal Ileum Cubilin Receptor Uptake

Placeholder sentence: cubilin-amnionless receptors internalize the complex.

• Cubilin/amnionless: Receptor (Placeholder short caption)
• Terminal ileum: Site (Placeholder short caption)
• Receptor-mediated endocytosis: Process (Placeholder short caption)
• ~3–4 hours: Time lag (Placeholder short caption)

Cubilin-mediated endocytosis in enterocytes

Placeholder short paragraph describing cubilin receptor uptake.

Placeholder highlight: ileal resection removes this absorption site.

Transport to Circulation via Transcobalamin

Placeholder sentence: transcobalamin carries B12 from enterocyte to blood.

• Transcobalamin II: Transporter (Placeholder short caption)
• Basolateral membrane: Exit route (Placeholder short caption)
• Portal circulation: Destination (Placeholder short caption)
• Liver B12 pool: Storage (Placeholder short caption)

Basolateral export and systemic delivery

Placeholder short paragraph describing transcobalamin-bound transport.

Placeholder highlight: liver stores buffer years of B12 supply.