How can you investigate the rate of absorobtion in the visiting tube experiment more quantitatively?
Comparisons between the time intervals can be made with a set of colour standards (known glucose concentrations) or a colorimeter to give a more quantitative set of results
A graph could be drawn showing how the rate of absorption changes with the concentration gradient between the inside and outside of the tubing
Limitations
Using visking tubing membrane as a substitute for the membrane of the small intestine:
Both are selectively/partially permeable
The small intestine has a much larger surface area due to the presence of villi
Using distilled water as a substitute for blood:
Both have an initially low solute concentration
The distilled water does not flow and so does not maintain the concentration gradient the way blood does
