4.5 Co-Transport

Co-Transport and Absorption of Glucose in the Ileum

• Microvilli to increase SA for absorption
• Movement of a substance against its concentration gradient is coupled with the movement of another substance down its concentration/ electrochemical gradient
• This is facilitated by symporters, which can transfer two substances in the same direction.
• An example of a symporter is the sodium-glucose symporter. It uses the sodium ions to move glucose into the cell. The flow of sodium ions through the symporter provides the needed energy for the glucose to move also through the symporter

1. %%Na+ actively transported out of epithelial cells & into bloodstream%%
2. %%Na+ concentration lower in epithelial cells than lumen of gut.%%
3. %%Transport of glucose/ amino acids from lumen to epithelial cells is ‘coupled’ to facilitated diffusion of Na+ down electrochemical gradient%%