Co transport

Question 1

The sports drink contains sodium chloride. Sodium chloride increases uptake of glucose in the small intestine.

Explain how

Answer 1

Sodium ions and glucose absorbed by co-transport;

Only penalise omission of ‘ions’ once in marking points 1, 3, 4
and 5

2. (Co-transport) via carrier / channel protein;

Accept via symport

Only reward reference to carrier / channel proteins in the context of co-transport

3. Sodium ions removed (from epithelial cell) by active transport into blood;
4. Maintains low concentration of sodium ions (in epithelial cell) / maintains sodium ion concentration gradient (between small intestine and epithelial cell);

Principle: marking points 3, 5, and 6 require consideration of ‘what moves’, ‘where it moves to’ and ‘how it moves’ to achieve credit

5. Sodium ions enter epithelial cells by facilitated diffusion taking glucose with them (from small intestine);

Reference to diffuse / diffusion for movement is required.
Accept facilitated diffusion

6. Glucose moved by facilitated diffusion into blood (from epithelial cells