A-LevelBiologyTransport in plantsOct/Nov 2009Paper 1 Q251 Mark
What is the sequence of events in the translocation of assimilates?
Aactive loading of sucrose into sieve elements via companion cells at the source, in
hydrostatic pressure, mass flow, unloading at the sink
Bhydrolysis of storage compounds in sinks, lowered water potential in sink, unloading o
sucrose from sieve elements down the water potential gradient, mass flow from the source
Clowered pressure in sieve elements at the source, movement of sucrose down the pressure
gradient from companion cells, mass flow down a diffusion gradient to the sink
Dmass flow of dissolved sucrose via companion cells into the sieve element at the source,
lowered hydrostatic pressure, diffusion of sucrose down concentration gradient to sink,
active unloading
✓ Correct Answer
The correct answer is A. This question tests the candidate's understanding of transport in plants within the Biologysyllabus. The examiner's mark scheme requires...
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Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
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