Cambridge AS & A Level Biology
7.2Transport mechanisms
Transport mechanisms in Cambridge AS & A Level Biology: what the syllabus expects you to know, the learning objectives and how to practise.
Subtopic59 practice questions3 lessons
Learning objectives
What the syllabus expects you to be able to do.
- 7.2.1State that some mineral ions and organic compounds are transported dissolved in water.
- 7.2.2Describe water transport from soil to xylem by the apoplast and symplast pathways, with the endodermis, Casparian strip and suberin.
- 7.2.3Explain transpiration as evaporation from internal leaf surfaces and diffusion of water vapour out.
- 7.2.4Explain how hydrogen bonding gives cohesion-tension in the xylem and adhesion to cellulose walls.
- 7.2.5Make annotated drawings of xerophytic leaf sections to explain how they reduce water loss.
- 7.2.6State that assimilates move in sieve tubes from sources to sinks.
- 7.2.7Explain how companion cells load sieve tubes using proton pumps and cotransporter proteins.
- 7.2.8Explain mass flow in sieve tubes down a hydrostatic pressure gradient.
Lessons
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Translocation: moving assimilates through the phloem
35 min
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Transpiration, the potometer and the cohesion-tension mechanism
40 min
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Water uptake: from the soil to the root xylem
30 min
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Sample question
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