H2 Biology Visking Tubing Practical: Dialysis Membrane Permeability, Osmosis and Evaluation
Q: What does Visking tubing model in H2 Biology?
A: It models a partially permeable membrane, letting students test osmosis and solute permeability while evaluating why the model is not the same as a living plasma membrane.
TL;DR
Visking tubing can show water movement by osmosis and selective movement of small solutes. It is useful for Paper 4 planning, controls, and evaluation, but it is not a living membrane: it has no proteins, no active transport, and no regulation. The strongest answers separate what the model can show from what it cannot.
Concrete example: If iodine turns the inside blue-black but the outside stays brown, iodine entered the tubing while starch stayed inside because starch molecules were too large to pass through the pores.
Use this after H2 Biology Osmosis and Diffusion Practicals and H2 Biology Core 1 Cell and Biomolecules.
Status: SEAB H2 Biology 9477 syllabus checked 2026-05-01. The Paper 4 apparatus list includes Visking tubing, and Core Idea 1 includes membrane transport.
1 | What Visking Tubing Models
Visking tubing is a dialysis membrane with pores. It can represent partial permeability:
- Water molecules can pass through.
- Some small solutes may pass through.
- Large molecules such as starch usually cannot pass through.
It does not represent:
- Membrane proteins.
- Active transport.
- Endocytosis or exocytosis.
- Selective channel regulation.
- Living-cell metabolism.
2 | Osmosis Setup
A common osmosis investigation uses sucrose solution inside Visking tubing and water outside.
Method pattern:
- Soak Visking tubing until flexible.
- Tie one end securely.
- Add sucrose solution.
- Tie the other end and blot the outside dry.
- Measure initial mass.
- Place tubing in water for a fixed time.
- Blot dry and measure final mass.
- Calculate percentage mass change.
If mass increases, water has entered the tubing by osmosis because the inside has lower water potential.
3 | Permeability Setup
To test molecule movement, a question may use starch, glucose, iodine, or Benedict's reagent data.
Practical course completion-record note
For practical, lab, and experiment courses, Eclat Institute maintains centre-held attendance records and may also issue an internal attendance or completion document based on participation and internal assessment.
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