| Membranes control the composition of cells by active and passive transport.
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| Understandings: |
Nature of science: |
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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.
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Experimental design—accurate quantitative measurement in osmosis experiments are essential. (3.1)
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| Applications : |
Guidance: |
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Structure and function of sodium–potassium pumps for active transport and potassium channels for facilitated diffusion in axons.
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.
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Osmosis experiments are a useful opportunity to stress the need for accurate mass and volume measurements in scientific experiment
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| Skill: |
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| Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions. (Practical 2)
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