AT

Question 1

Co transport

Answer 1

1. Sodium ions are actively transported out of the epithelial cell into the blood by the sodium potassium pump
2. This reduces the sodium ion concentration in the epithelial. cell.
3. Sodium ions can then diffuse from the lumen down their concentration gradient into the epithelial cell
4. The protein the sodium ions diffuse through is a co

transported protein, so either glucose also attach and are transported into the epithelial cell against their concentration gradient

5. Glucose then moves by facilitated diffusion from the epithelial cell to the blood.