Understandings:
- Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport.
- The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis. Vesicles move materials within cells.
Applications and skills:
- Application: Structure and function of sodium–potassium pumps for active transport and potassium channels for facilitated diffusion in axons.
- Application: Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis.
- Skill: Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions. (Practical 2)
Guidance:
- Osmosis experiments are a useful opportunity to stress the need for accurate mass and volume measurements in scientific experiments.
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Utilization:
- Kidney dialysis artificially mimics the function of the human kidney by using appropriate membranes and diffusion gradients.
- Syllabus and cross-curricular links:
- Biology
- Topic 6.5 Neurons and synapses
Aims:
- Aim 8: Organ donation raises some interesting ethical issues, including the altruistic nature of organ donation and concerns about sale of human organs.
- Aim 6: Dialysis tubing experiments can act as a model of membrane action. Experiments with potato, beetroot or single-celled algae can be used to investigate real membranes.
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