BRAINCAKEAbsorption in the Ileum
Absorption of digested food occurs in the ileum of the small intestine. At the beginning of the small intestine, ions are pumped into the lumen from the epithelial cells. The water potential is lower in the lumen of the small intestine than the epithelial cells and water moves from the epithelial cells lining the small intestine to the lumen by osmosis.
Further along the small intestine ions are pumped back by active transport. The water potential is now lower in the epithelial cells. Water moves from the lumen to the epithelial cells by osmosis. Glucose is absorbed by active transport.
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Key terms in this lesson
- diffusion
- The net passive movement of molecules or ions from a region of higher concentration to a region of lower concentration, down a concentration gradient.
- facilitated diffusion
- The passive movement of molecules or ions down their concentration gradient through protein channels or carrier proteins.
- osmosis
- The net movement of water molecules from a region of higher water potential to a region of lower water potential through a selectively permeable membrane.
- water potential
- The pressure created by water molecules, a measure of the tendency of water to move out of a solution; pure water has a water potential of zero and solutes make it more negative.
- active transport
- The movement of molecules or ions across a membrane from a region of lower to higher concentration, against the concentration gradient, using ATP and carrier proteins.
More in Transport Across Cell Membranes
- Osmosis
- Osmosis in Animal Cells
- Osmosis in Plant Cells
- Active Transport
- Sodium-Potassium Pump
- Increasing the Rate of Movement across a Membrane
- Co-transport in Absorption
- Oral Rehydration Therapy
All 22 lessons in Transport Across Cell Membranes · All AQA AS-level Biology topics