4.5 Co-transport and absorption of glucose in the
Increasing the movement across membranes
- Epithelial cells lining the ileum possess microvilli collectively forming a brush boarder. The microvilli provide a larger surface area for the intersection of carrier proteins through which diffusion, facilated diffusion, and active transport can take place.
The role of diffusion in absorption
- As carbohydrates and proteins are being digested continously there is normally a greater concentration of glucose and amino acids within the ileum and the blood.
- Thetre is a concentration gradient down which moves the glucose via facilitated diffusion.
Role of active transport in the blood
- Diffusion only results in an equalibrium is reached in the intestinal epithelium. This leads to not all amino acids being absorbed.
- All amino acids or glucose are pulled into the cell by co-transport of sodium ions that have been actively transported out by the sodium potassium pump. .
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4.5 Process of co-transport in the ileum
- 1. Sodium ions are actively transported out of epithelial cell, by the sodium-potassium pump. This takes place in one type of protein-carrier molecuel found in the membrane of epithelial cells.
- 2. This maintains a much higher concentration of sodium ions in the lumen of the intestine and that of the epithelial cells.
- 3. Sodium ions diffuse into the epithelial cells through a different type of protein carrier in the cell surface membrane.As the sodium ions diffuse in through the seocnd carrier protein , they carry either amino acids or gluecose molecuels.
- 4. The glucose/amino acid molecuels move into the blood plasma by facilitated diffusion using another type of carrier protein.
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