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1.4 Membrane transport

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Description

Nature of science:
Experimental design—accurate quantitative measurement in osmosis experiments are essential. (3.1)
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.
 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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