Explore how auxin activates genes and proton pumps, acidifies the apoplast, loosens cell walls and enables water uptake, elongation and bending in IB Biology HL C3.1.21.
Plants have cell walls composed of cellulose.
When a plant cell grows, the cell wall must expand. Explain the role of auxin in cell wall expansion.
a. auxin causes (specific) genes to be transcribed/expressed;
b. stimulates proton pumps/causes movement of hydrogen ions into cell wall/through plasma membrane;
c. hydrogen ions/low pH/acidity loosens connections between cellulose (microfibrils/fibers)
OR
hydrogen ions/acidity activates expansin / expansin breaks/reforms connections between cellulose;
d. loosened cellulose can move apart/separate so wall becomes weaker/can expand;
2
Marking guidance:
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Clarity of communication: [1]
The candidate's answers are clear enough to be understood without re-reading. The candidate has answered the question succinctly with little or no repetition or irrelevant material.